Harshness, Clicks and Pops
Printed From: Graham Slee Hifi System Components
Category: And the rest
Forum Name: Amplification
Forum Description: Share your interests or views on amplifiers, preamps, etc
URL: https://www.hifisystemcomponents.com/forum/forum_posts.asp?TID=5144
Printed Date: 19 Apr 2024 at 5:18pm
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Topic: Harshness, Clicks and Pops
Posted By: Graham Slee
Subject: Harshness, Clicks and Pops
Date Posted: 31 Jan 2021 at 11:26am
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Through Big-Tech, Moore's law has hammered home that subtle artifacts make a difference - sometimes explosively. I watched a video explaining "n -pn" leakage, that in nanometer technology, it caused Latency, so off isn't off entirely. They knew about this before they embarked on transistor stuffing many years ago, but I'm surprised by how such things are ignored in audiophile circles. They seem to be more interested in the magical stuff of zero scientific connection. It could be due to a lack of scientific education. Leakage current exists in common or garden silicon, too - things like power transistors, discrete small-signal transistors, and the transistors that make up a silicon chip such as an op-amp. Could the Early voltage be related? Maybe, but the point I'm making here is old technological understanding gave way to a new technical understanding, with minimal in the form of transitional fossil evidence. To put it another way, the language changed. It might mean much the same as it used to do, but we can't catch them up to ask. James Early discovered that on-ness increased with on-ness, but Moore's suffers from off-ness being less than off-ness. Early has little effect on Moore's because switching is "different" to analogue. All I can discuss is what I do, not what they do. The point is that transistors are not the clean devices many take for granted while indulging in their other-world esoteric pastimes. One interesting word popped-out of the video, which is Latency. In the word Latency, we can see another word, Late. We can add the letters n and t to obtain Latent from Late. We can observe Latent if we are near a brick or stone building in the summertime. Early in the day, with temperatures rising, the building feels cool. Near dusk, with temperatures falling, the building feels warm. That is Latent Heat. Therefore, Latency can describe a stickiness, where things don't change the instant we'd like them to change. Big-tech discovered that Latency is the spanner in Moore's law as far as silicon is concerned. It brings Moore's law to an end. Looking back, they showed the valve (tube) as having significant Latency, followed by the bipolar transistor, the FET, and then nano-transistors. Even though the valve has the speed needed for high power-high frequency work to this day, it suffers the worst leakage. This leakage is such that it doesn't switch off sufficiently, so power is wasted. As junctions between materials become narrower, leakage becomes a problem, and now they're at 3D - building upward - so that 2D can be shrunk further. Can any of this benefit audio? Some say the same characteristics cannot exist at audio frequencies - that they live at GHz and THz frequencies. As if by a miracle, they do not exist at MHz or kHz. Instead of a complete building on a summer's day, shall we use a single brick? Latent heat might not be easily felt by hand, but we can establish more accurate measurement, and using it, we can find there is Latency of temperature. Therefore, some of what exists up there can exist down here. During my research for this part of this topic, I could not find any correlation between the words Late, Latent, and Latency, which I thought rather odd. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Replies:
Posted By: Godra
Date Posted: 01 Feb 2021 at 12:30am
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Pretty interesting read Graham. Thanks for sharing! Like you said, it's funny how all things digital are always advertised as perfect. I think we are misled in this case. When we think about digital, we instantly have in mind that there is only two value that sums up everything : '0' (false-no voltage) and '1'(true- voltage). This suffers no ambiguity. This lack of ambiguity is to me the hallmark of all thing digital. Though, in reality, from what I have read on digital to analog converter , it seems that some '1' can be seen as '0' and conversely... ------------- Clearaudio Performance DC with Clarify tonearm + Virtuoso V2, Tannoy Legacy Eaton, Accession MM and BAT VK300Xse |
Posted By: Graham Slee
Date Posted: 01 Feb 2021 at 5:53am
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It could be said that a nano-transistor has no capacitance; instead, it's one of those cases where it's so small it can be neglected. Capacitance is another "show-stopper" for semiconductors - it gets bigger as the device gets bigger. It begins to get troublesome in discrete transistor circuits, becoming far worse in power amplifiers. The larger the area of each layer of silicon that come together to form collector, base, and emitter, or source, gate, and drain, the larger the capacitance. The junction between the gain elements - collector to base, or drain to gate - is worsened by voltage gain - whatever its capacitance, it is multiplied by its gain. Power transistors come off worse due to the physical size of the junctions. Valves (tubes) suffer significantly from capacitance considering their high impedance - big Rs combine with Cs to roll-off the highs. It led to the development of the tetrode (one extra grid) and the pentode (two extra grids) to split the inter-electrode capacitances and reduce the total capacitive effect. The choice for a low-distortion preamp stage was always the pentode. It could be used for accurate in-loop EQ because it didn't run out of high-frequency gain as a triode does. A triode inside an EQ network would suffer poor high-frequency accuracy, and failing to control transients, would output considerable distortion and exaggerate click and pops. The triode was often relegated to the cheaper (mono) record player, where its 5% THD didn't matter much. Using a dual vacuum tube and passive EQ in between, sufficient gain could be had from a simple tube. Incredibly, over recent years, this circuit has found its way into the audiophile market. The valve takes its place at the head of the latency hierarchy, followed by power transistors, small-signal transistors, and then chip-level fabricated transistors in such as operational amplifiers (opamps). The 1960s silicon revolution rapidly supplanted the valve in small-signal applications. When combined inside innovative configurations, the discrete transistor, available in both NPN and PNP, could do more and do it without as much noise. Impedance had come down an order of magnitude. Large value resistors generate more noise than small value resistors, and so noise is reduced in that ratio. However, the capacitance was still a problem, and without the ability to add "grids," other techniques had to be found. Oscillation had been a problem for valve voltage followers (cathode followers or common-anode amplifiers) - these being used as output buffer stages. The transistor suffered so much from it that it was almost reinvented as a passive amplifier. The difficulty caused by capacitance resulted in negative resistance. Semiconductors are not only used for amplification or switching; they are also used for oscillators to generate the frequencies needed for radio communications. Oscillators exist in both transmitters and receivers. In a receiver, they are used to demodulate carrier frequencies. Transistor output buffer stages (emitter followers) bear a more than a striking resemblance to the Clapp version of a Colpitts oscillator. A buffer stage in a preamp often follows a volume control, and the stage might be oscillating at some considerably high frequency, well beyond our hearing range. A give-away is "early wear-out" of the volume control, which results in a crackling sound. This is simply the accidental oscillator changing and stopping and starting in frequency as the pot is turned. Not all crackling volume controls are due to this, mostly if they've done good service for a few years - that's just debris accumulation. The discrete transistor designer might find more headaches than bargained for, and for what reason? Do discrete stages work better than a suitable alternative fabricated onto a silicon slice? The operational amplifier design has had to pass the tests of not oscillating or working within a specification where oscillation is guaranteed not to occur. The opamp might not contain romanticism but has reduced latency and better frequency control within limits. Not all opamps are better than discrete in all applications, but they beat discrete hands down in some applications. Much depends on the designer's experience. There's a place for everything, and all applications are different. We should now be aware that leakage, the Early effect, and now capacitance, have a significant bearing on how any particular circuit performs. More to follow. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Speculator66
Date Posted: 01 Feb 2021 at 2:55pm
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When I was buying my first system - many years ago now - I bought a Wharfedale Linton amplifier. My mother heard it and said she would like one as well so one was secured for her. Not long after she got it, she complained to me about hissing down one channel. It turned out that the amp worked fine for 15 mins or so before the hiss started. It was duly returned to the Rank Wharfedale Service department, not once, but twice. They said that they couldn't find anything wrong with it. So I, as a young lad beginning to learn about electronics stepped in and looked at it. She was absolutely right and my thoughts turned to capacitors and transistors. On taking the cover off I was greeted by a beautifully simply design - i'm not talking electronically but layout. There were four plug-in boards, two for each channel. My simplistic mind said, swap the boards and see which one changes the channel it's hissing on. I identified the bad board within only a few minutes and then started to replace the transistors one at a time. Second time lucky - there were only six anyway. So, can transistors cause noise problems such as hum and hissing ?No doubt about it. That amplifier is still working away in my workshop - currently through some old KEF 104ab Mk II's and it is now ca. 50 years old. Never had a problem since. |
Posted By: Graham Slee
Date Posted: 02 Feb 2021 at 7:13am
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Transistors used to be different from op-amps because, at first, there were just transistors made from ingots of doped germanium, and so, op-amps were discrete assemblies of a number of them. Today, transistors do not have superiority over op-amps - they are equivalents. When you see somebody boasting the superiority of transistors over op-amps, they are being incredibly big-headed about being able to assemble a number of elements better than a chip manufacturer. Then again, we all make mistakes! To realise your mistake, you would need considerable experience in developing circuitry with both. An op-amp is not a ready-made amplifier; it is a greater part of one than a single transistor. If you need a complex solution, the op-amp out-performs a board full of transistors. If you need a simple solution, one or a few transistors might be more suitable. It was an awkward process making transistors from an ingot of germanium (or silicon). Still, by adopting a similar approach to how printed circuit boards are made, it became possible to print and etch transistors by the one, or by the many, on a silicon substrate. The ingot method was problematic in attaching the wires. The planar process solved that problem. Bill Shockley's ingot method produced tiny single transistor slugs that could be clamp-wired either end, but the difficulty was sticking the base wire into the middle of it. You can't solder or weld a wire to a rock! Eight of Shockley's team moved down the road and developed the print and etch method, which allowed the deposition of metal, and thus the ability to accurately and reliably spot weld the wires. The company they formed was Fairchild, which could make a single transistor on a chip, or many transistors on a chip, and a combination of N-doped and P-doped transistors, on a chip. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 02 Feb 2021 at 10:45am
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As a youth, leaving alone my disco work on ceramic cartridge stages, my first home-made magnetic cartridge phono stage used a 741 op-amp, and the EQ was in its feedback. 50% of its improvement over my amplifier's built-in stage was psychological - because I'd built it! The 741 was the most easily implemented op-amp of its time. The "designed for audio" NE5534 did not make its debut until the late '70s and didn't hit the hobby shops until much later. I'd spotted a passive interstage preamp in a Tandy book about valves but could see any two gain stages could be used and set about making it with 741 op-amps. The result was revealing! Over the years, I had difficulty understanding how 741's were able to sound so good. Pouring over valve datasheets many years later, the reason for the 741's success jumped out of the page. The RCA design was made for a cheap but low noise, twin triode valve (today's equivalent is the 12AX7). Remember that I previously remarked on triodes' capacitance limiting their high-frequency performance? This valve also had very poor distortion. By comparison, the 741 was light-years ahead. Nearly everybody making phono stages today uses the same basic circuit, and some use three amplifier stages with two passive filters. I don't think they'd use 741 op-amps, but maybe the NE5534 or NE5532 dual cousin. Now, some declare that their's is a discrete transistor design, which to some might appear smart, but having been there, I beg to differ. The great thing about the passive interstage is it does help with the harshness, clicks, and pops. The interstage EQ is also the equivalent of a scratch filter - it attenuates any instability in the gain stages to a degree. That degree might not last, depending on the capacitors used in the filter. But first, we need to understand the filter's behavior. A single-stage filter is similar in many respects to a tone-stack. In the case of RIAA, it is a low-pass filter with a step. It rolls off the highs given a starting point of 50Hz (this is called a pole), and then stops doing so at 500Hz (this is called a zero), then starts rolling off again from 2122Hz (the second pole). Now, that would be fine if the driving impedance of the gain stage was very low - low, as the output of a 741. A class-A transistor output has considerable collector resistance, just like the original RCA valve circuit had significant anode resistance. On positive half-cycles, the resistance adds to the filter, and on negative half cycles, it isn't there. And so, what you have to do is average it out on test, using an audio analyser, tweaking values as you go. To avoid this problem, the output of the first gain stage can be made push-pull, resulting in distortion problems due to gm-doubling - or not - which depends on signal level (loudness). The op-amp has this "pre-sorted." Another problem is the capacitors and their dielectric absorption - because, in a filter, they charge and discharge. Should they be slow or inductive, they will not attenuate immediately to the correct level, and so clicks and pops might be exaggerated. The leading edge of a note might be exaggerated too. If we also have a single-sided drive signal - a collector pulling down on the negative excursion and a resistor pulling up on the positive, depending on the first gain stage's absolute phase, some instruments sound different. The trumpet is an excellent example of an instrument favouring one half of the cycle over the other. By setting the filter impedance ten times the collector resistance, this problem is minimised, but the high-value filter resistors add their noise. That's OK if you can put up with a bit of hiss, and if it's a valved stage, you'll probably expect hiss. The filter capacitors ought to be fast to remove leading-edge exaggeration, so we can employ polypropylene types here. As long as they're not those audiophile wound ones, which are inductive (even if they claim otherwise), things should improve. However, not all polypropylene capacitors are equal, and some still lead to an exaggerated sound. By and large, the biggest problem is the channel mismatch. Even using 1% components, the driving impedance difference per half cycle moves the leading edges away from the averaged level, such that the stereo image drifts and sometimes rapidly shifts, confusing the sound stage. I made phono stages this way for many years, gradually learning why the 741 op-amps passive phono stage sounded good when its specification would suggest otherwise. It was blunting the edge. One further observation was reading the technical hi-fi blurbs, which made much of pure resistive negative feedback in the gain stages. As the gain stages were multi-transistor, there must therefore be excess-phase. Although non-destructive, the lack of capacitive compensation leads to high-frequency oscillation (well beyond the audible range). Although, with passive filters blocking it from escaping the phono stage, it could have a very "dry" sound, which became ever more evident the more prolonged the circuit was left on. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 03 Feb 2021 at 9:42am
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To supplement my last post I include illustrations of passive RIAA stages.  A block diagram illustrating the basic workings of a dual gain-stage with passive RIAA EQ.  ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 03 Feb 2021 at 8:12pm
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Another image where the effect will be seen by those with a smattering of technical understanding. This is a single sided class-A amp with a collector load resistor (Rc, Ro is the "Early resistance"), and is virtually the same as the input valve in the RCA circuit. So, you think your phono stage is reproducing sounds like real? (it depends on its configuration) This doesn't.  ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 03 Feb 2021 at 9:04pm
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Take another look at the above image. If the instrument waveforms shown are in-phase, and the first gain stage inverts, the waveforms invert. Although this has no bearing on what comes out of the loudspeaker, the passive phono stage, driven class-A inverted, will give the instruments a different sound to a non-inverting first gain stage. If the sharp "edges" point one way, and that way gets smoothed by the blunt side of the 2nd harmonic as well as the RIAA turning over at a lower frequency on that half-cycle, it might appear warm. If the circuit was such that the opposite occurred, it might appear harsh! Clicks and pops caused by hairline scratches, micro-bubbles in the vinyl, and debris, might well be "stretched" on one half-cycle and "narrowed" on the other. The amount heard will depend on the loudness of the signal. The louder the signal, the more pronounced the difference is as far as the 2nd harmonic is concerned. Now, if driven by a class-B output stage such as the humble 741 op-amp, there are no half-cycle differences. I'm not saying the 741 is good, just that there is an obvious difference. We're not talking about component subtleties; we're talking about real things. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Sylvain
Date Posted: 04 Feb 2021 at 10:52am
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I'd spotted a passive interstage preamp in a Tandy book about valves but could see any two gain stages could be used and set about making it with 741 op-amps. The result was revealing! Over the years, I had difficulty understanding how 741's were able to sound so good. Pouring over valve datasheets many years later, the reason for the 741's success jumped out of the page. The RCA design was made for a cheap but low noise, twin triode valve (today's equivalent is the 12AX7). Remember that I previously remarked on triodes' capacitance limiting their high-frequency performance? This valve also had very poor distortion. By comparison, the 741 was light-years ahead. Nearly everybody making phono stages today uses the same basic circuit, and some use three amplifier stages with two passive filters. I don't think they'd use 741 op-amps, but maybe the NE5534 or NE5532 dual cousin. The discussion is of great interest but my ability to contribute to the Technical aspect is very limited ,,,However....I was advised by another Audio Design Engineer some 15 years ago to change NE5534 for the then modern OPA 2015!!!!!!! of a well known Texas instrument company .......and then The discussion between the WHY and the Merit of Passive and Discrete was still OP AMP were not fully arrived as yet .....BUT OP AMP development versatility seem to have overcome the argument over Discrete case specific application Apologies for my interruption BUT teh subject is highly IMPORTANT to my Audio components upgrade and development
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Posted By: Graham Slee
Date Posted: 04 Feb 2021 at 11:49am
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Another problem with the passive phono stage is the flat gain stage (how could it be any other?) between cartridge input and the passive filter. The passive filter has an insertion loss of -19.3dB - as near as damn it, 1/10. For a regular MM gain of 40dB (x100), each gain stage must share a gain of 1000 (60dB). It makes sense for best noise performance to put most of the gain upfront, but you'll see the calamity in doing so as I continue to explain. For the sake of this discussion, we'll share the gain between the two gain stages. The square root of 1000 is 31.6227766, or we could divide 60dB by two. 30dB expressed linearly is also 31.6227766. That's a bit cumbersome for a discussion, so let's call the input gain x30. If we were to use op-amps, the supply is generally 30V (+/-15V dual-rail), and datasheets tell us the output swing into their rated load. Mostly that's 10V rms. The cartridge output might be 5mV. Some output 6.5mV, others 3mV, and so on. A particular Stanton does 9mV. However, we'll stick at 5mV. Vinyl can achieve 14dB headroom. However, it's doubtful if the highs go so loud, as most styli would skip on the inner groove, but perhaps we can use the studio PPM of +8dBu (x2.5). The cartridge's rising output, helped by record EQ, means that the reference 5mV at 1kHz is 50mV at 20kHz, and multiplied by 2.5 is 125mV at 20kHz (merely taking the inverse of the RIAA filter as evidence). Multiply 125mV by the gain of 30, and you get 3.75 volts. The maximum swing on a 30V rail op-amp is 10V, so the difference is x2.67 or 8.5dB. So, the headroom here is just 8.5dB. What does the spec of the advertising blurb say? I'd hazard a guess it doesn't admit what we just discovered. Now, at the bass end, the cartridge outputs 0.54mV (5mV at 1kHz minus the 19.3dB of the RIAA curve). The gain stage outputs 30 x 0.5 = 15mV. The op-amp is "flying" at HF, and then there's the weedy bass signal at just 15mV - hardly linear gain. But what about the scratch, or the microbubbles, the debris, or a little mistracking? The scratch's leading edge will be in the upper-frequency end - a transient - and what voltage will that produce? Hopefully, it won't result in the first gain stage outputting more than 10 volts? What if it did try to output more than 10 volts? Well, it would clip, wouldn't it? With low-frequency noise being a problem in most amplifier stages (op-amp or otherwise) - what the technical type understands as 1/f noise - we really should be making the first gain stage have more gain. But if we do, we drive the HF transients further into clipping. The problem is that we need to spec the lowest noise to the customer, so we're now stuck. We could increase the power supply to give us more headroom, but to do so meaningfully, we'd need around 90 volts. That might seem crazy, but I've seen it. You cannot use op-amps anymore, so your circuit is discrete, and you're now competing with Silicon Valley. But, continuing with our down-to-earth power supply voltage and accepting that clipping will happen at HF (but omitting to tell the customer), then perhaps the passive RIAA filter will help. Well, yes, as in all RC filters, a square wave (the result of clipping) will change shape and become "more rounded," and so the passive EQ phono stage just about gets away with it. Compared with the early solid-state feedback EQ, the passive interstage RIAA is far in advance. I made plenty of different passives, and my ears can vouch for that! But compared to the pentode feedback EQ, they may not fare so well. The difference here is due to the pentode valve's high-frequency performance and the fact that it had a lot more (HT) power supply headroom for a thing called overshoot. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: patientot
Date Posted: 04 Feb 2021 at 3:05pm
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The stuff I see posted over and over on audio forums is that "passive RIAA is better" and "active RIAA is bad". A few manufacturers make a big deal of this and tout their passive RIAA phono stage as having "less prominent clicks and pops" and a "more natural sound" than anything with active RIAA. Honestly the worst phono stage I had in terms of sounding harsh generally and amplifying clicks and pops and surface noise was a passive RIAA one. It had great looking specs on paper but was plagued with problems in real life. It seems to me that whether a phono stage amplifies clicks and pops and harshness comes down to very particular aspects of the design, not whether it uses active RIAA or passive RIAA. Another thing of note - there is one newer company that has recently made the rounds on some forums that heavily touts their discrete, passive RIAA approach. I'm not out to bash this particular company or anything so I won't mention names here. I'm seeing people recommend this company's products over others solely due to the design approach and nothing else. Again, very few people have actually heard the units because they are so new. The product may well be decent or even excellent, but that seems a bit misguided to me. ------------- SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges. |
Posted By: Graham Slee
Date Posted: 04 Feb 2021 at 4:22pm
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Hi Sylvain, A word or few about op-amps. Study the internal circuit of an op-amp from its datasheet (where they dare to show it), and you'll mostly see a common or garden transistor amplifier with a few enhancements. To meet op-amp science requirements, it must have a "universal" power supply range. So you'll see a voltage reference that you'd not usually see in a proprietary amplifier design. In a single op-amp, you'll also see offset null pins used to trim the device for some scientific applications. Otherwise, they generally follow the same path. We hear a lot about Burr-Brown, but until 1983, little was known about this 1956 established company. It was taken over by Texas Instruments 17 years after making its second debut (the year 2000). It worked in precision digital signal processing, so I can see how the audiophile might associate with that. Analogue Devices are similar to what Burr-Brown was, but Texas could see the value in milking the audiophile cow using the Burr-Brown tag. Shall we take a technical peek? Perhaps the OP275? But wait a minute, that's an Analog Devices op-amp. Well, maybe Kevin Brown, whose company owns the patent, could be a relation of Thomas Brown, jr. but I'd be wasting my time finding out. So, what's the patent all about? We read about the Butler input stage, so we take a look at the patent, and it uses two FET transistors to pad-out a Wilson current mirror. After it became apparent that a Wilson current mirror could be improved by adding emitter resistors, like fries, they came with everything. The patent states these are FET resistors, and that's sufficient novelty to grant a patent. Its correct use is to reduce input noise, and compared with the nearest equivalent (LF351, in my opinion), the only main difference is that the LF351 uses 1k3 resistors instead of gate-drain shorted FETs. It makes 7nV per sq. root of frequency range. That's a 6dB noise improvement for those capable of making use of it. Other circuit noise sources might drown out the improvement, and in which case, what difference is it going to make to your ears? Skipping to the favourite pastime of chip-rolling, there are scores of partially technical proponents of high slew-rate op-amps all over the internet. The formula for the power supply capacitors in "Talkin' PSUs" Q = CV = IT also applies to slew rate, except, looking at the chip-rolling antics, it would seem that science has nothing to do with it. If you don't know how an amplifier circuit works, you won't see what you're doing with an op-amp - it's that simple. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 04 Feb 2021 at 4:28pm
All I can really say is that I've pointed out the pitfalls as simply as I can translate them, and if they didn't exist, I'm sure I'd be making passive stages. And I've built plenty of them. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
patientot wrote:Posted By: patientot
Date Posted: 04 Feb 2021 at 6:14pm
They certainly do milk it from what I've seen. Browsing online or the catalogs I've seen, any product that has a chip from the brand is always advertised as such with ad copy specifically pointing it out, not just flatly stating it in the specs section.
I never understood the point of changing op-amps in a piece of equipment like that. I guess some people think that all manufacturers use the "wrong" op-amp or the "cheapest" one or whatever. Maybe they never thought the equipment was designed to be used with a specific component and that changing it might have unintended consequences. Then again you also have companies like this telling us we "need" to switch out our op-amps. https://sparkoslabs.com/discrete-op-amps/ - https://sparkoslabs.com/discrete-op-amps/
------------- SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges. |
Posted By: Sylvain
Date Posted: 04 Feb 2021 at 9:06pm
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Thank YOU all for very useful contributions ...... I now dream of a Pentode driven Pre-amp fed from 'Genera'' or Line level output, 6volt Mac Pro Transport or my WALKMAN Cassette portableCD player to feed DAC and Proprius, bypassing the electronic Pot pre-amp......perhaps, holding my breath, for DAK badge front plate and circuit board.
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Posted By: Graham Slee
Date Posted: 07 Feb 2021 at 11:36am
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I thought I'd clearly expressed the reason for this topic on page 1 - maybe Grammarly is changing my plan? I only got it as a spell-checker -- oh dear, I meant spelling checker. Perhaps it's putting a spell on my topic. Maybe it's flipping what I meant to say! Did you ever see "Life of Brian" by Monty Python? In the scene where the woman shouts "look, the holy gourd," but it's too late, a guy yells, "look, the holy slipper," and the crowd runs after that instead. In my lifetime, I discovered the peculiarity about hi-fi is its willingness to pick up on any fad, and the hoards of zilch knowledge think they learned something new and run with it. The problem is "separates." If you're into tripping, you might get lucky and have sounds from down the garden, out in the square, Hendrix walking behind you, sounds appearing from behind walls - spooky! Yes, the problem is "separates," and most don't get lucky. But I'll not dwell on trippy sound stages because I know how it's done, and I lost interest because, after a while, you want music the way it is. Harshness, Clicks, and Pops is what this topic is about. There are real physical things that emphasize them, and equally, there are actual physical things that can do the opposite. If we stop a while, we might discover a few things, when we buy something that's supposed to make it better, why it doesn't. The problem is our choice of separates and/or how we use them. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 10 Feb 2021 at 8:51am
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Today, it might seem I'm going off-topic. As Dr. Jones said, "you can learn a lot from what you know." He was talking about observations. Say if you wanted to learn about high impedance, low impedance, and transformers; firstly, you could look into the outside air to see if there are any overhead power lines. The power in this country is alternating current at a frequency of 50Hz. You could get an old 64-ohm live-chassis TV speaker in series with a 40-watt lightbulb (remember them!) and wire to a 13A plug, but I wouldn't recommend it. However, by doing so, I taught myself (aged 9) what 50Hz sounded like. Going a little off-topic, it made an excellent spark transmitter. By tuning the "steam radio" between stations and chopping live or neutral wires, bareing their ends, and flicking them together, the radio responded with a hard click-clop sound. The click-clop sound became louder by winding several turns of insulated wire around an old jam jar and putting them in series with the speaker and light bulb. As is the law, I have to tell you not to do this at home! It is incredibly dangerous, and the 240 volts 50Hz ac current gives you a right jolt of a tickle up your arm and into your chest! No, don't try this at home. You might think it somewhat remiss of mum and dad letting me do this, but they didn't know what I was up to. If you've ever looked into a consumer unit - the box with all the fuses/circuit breakers in it - you might note that the live, neutral, and earth busbars are chunky pieces of copper. There might be other houses on your street/lane/road? They also have consumer units containing hefty busbars. If you laid all the busbars (let's choose the nice looking neutral ones) in a suburban street side by side, and if they magically became plasticine, you could squeeze them together (without increasing their lengths) and mould them into a large cylindrical shape - I think you'd need two hands - it would be a large diameter cylinder! It might be that there are 100 houses surrounding an electricity "sub-station," and so we need more plasticine! The eventual cylinder's diameter is the neutral conductor's diameter required to carry the current for all those houses. You'd have the same diameter for the live conductor. Woah! That's some incredibly thick cable! However, the overhead cable, which carries all that power, is only about 12mm in diameter (don't climb up to check!) It doesn't compute - how can that be? Don't miss the next thrilling installment! ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 10 Feb 2021 at 6:38pm
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The 12mm diameter overhead cable might be able to drive 100 amps, sufficient for one house, but might drive 12,000 amps, enough for all the homes on the local substation; how come? The answer is the transformer. The substation has a bank of transformers - great big things painted grey with oil-cooled windings. The overhead cable might carry 30,000 volts. When transformed to 250 volts for the houses, the ratio is 120:1. The voltage reduces, and the current increases. It's that last thing you need to remember: voltage reduces, current increases. It can go the other way, too - transformers can step-up voltage, and when they do, the current steps down. The heavier the load, the more current you need. Now, consider the transformer "preamp." It can transform voltage up, and so its output current is transformed down. Yes, I know the blurb says different, but physics is the boss! Impedance (ac resistance) is related to voltage and current by ohms law. Ohms law used to be taught at secondary level in British schools, but it's one of those things that is easily forgotten unless you work with it daily. If your transformer "preamp" has an input impedance of 100k and transforms up to give a gain of 10, its output impedance is 1meg. I don't have much patience to continue trying to explain the bollocks expounded by these pirates, so if you didn't understand, well, you never will. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Sylvain
Date Posted: 10 Feb 2021 at 8:13pm
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.....''If your transformer "preamp" has an input impedance of 100k and transforms up to give a gain of 10, its output impedance is 1meg. I don't have much patience to continue trying to explain the bollocks expounded by these pirates, so if you didn't understand, well, you never will.''' Just when It was getting interesting .....perhaps a cup of Yorskhire tea and scones and another try on sunny day ...but would wait .....holding my breath ..
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Posted By: patientot
Date Posted: 10 Feb 2021 at 9:00pm
Understandable. I think I've got the gist of it. Thanks for taking the time to explain things. ------------- SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges. |
Posted By: Graham Slee
Date Posted: 11 Feb 2021 at 6:39am
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There's a firm registered in Cambridge which gets its products for free, from China. It's the only way it can turn a profit. It seems to have gotten the interest of HMRC. The owners either own a yacht or like having their photos taken on one. Somewhere in Europe, there's a millionaire who dabbles big time in hi-fi, with world-wide distribution, hubris, arrogance, the lot. He was quoted by an ex-distributor in Canada saying, "if Slee gets too big, we'll bust him by copying his circuits." Many smaller "outfits" struggle a bit upstairs when it comes to electronics, but that doesn't stop them; they'll use transformers instead... They have one thing in common - they have the best copywriters on the planet (or copy them) who know the secret of the bullsh*t that gets your juices flowing. The mantra is repeated so often, and you drool over the hype because it's so obviously the promised land. Why join this forum? Perhaps a few think it sport to rile up a Yorkshireman? I like Cheshire cheese; it's crumbly. Dover's white cliffs are also crumbly, but I bet it doesn't taste like Cheshire cheese. Chalk and cheese! One meg into 22k doesn't work, but don't let that spoil your valve dreams. Compatibility never seems to enter the minds of those who are gone. Hi-fi is not an industry; it is a collection of ego-trippers who are good at dark sentences. So, you have a problem with harshness, clicks, and pops? Things don't sound right? So you rush round in circles comparing this with that - looking at this link or that link - what Mr Forum Anonymous thinks. To this day, I get t**sers emailing me thinking I need help. I don't need any help, thank you. But I do honestly believe there is a massive mental health problem. There must be, because even when I send them to this link https://patents.google.com/patent/US20170126186A1/en - https://patents.google.com/patent/US20170126186A1/en they continue to go on and on about how childish little things are better (in their minds). If the above describes you, then you're in the wrong place. I'd rather talk with a small group willing to learn than a large group of deceived, challenging to get on with, Sheople. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Sylvain
Date Posted: 11 Feb 2021 at 7:54am
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Cambridge to Vienna to Shenguang cause music to resonate, emancipates and evolve.... Science and it's physics confound to cause once great Eurica moment and another to sheer sterility. The genius is in man and not his measuring tool and man drive the science and Not Science drive the man. I am not sure whether Confusius would so state and no technical link to explain.
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Posted By: Graham Slee
Date Posted: 11 Feb 2021 at 8:08am
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While working, I fancied listening to some music, so I set up a record deck, found a surplus amp from out of the loft, bought some tiny JBLs, hooked it all up with a Gram Amp 2, and it sounded awful! I'd committed every sin in the book - I mean - what did I expect? It had to have been a fit of lunacy! Firstly, the room. At the time, I was huddled into the "dining room end" of a narrow kitchen - my office at the time. If I'd ran the Amroc acoustic calculator, it would have told me the room had terrible acoustics. Lacking space, the only position for the tiny JBLs was the room corners - on wall brackets. Should have known better? I shall not name the amp, but although from a world-famous manufacturer, it wasn't very expensive, it still used its 1980's polystyrene capacitors, which made it sound - polystyrene. So, I went back to using headphones driven by a Solo hooked-up to the Gram Amp 2 and standing on the headphone cable nearly every time I stood up! So annoying, and the reason I'd wanted to be on speakers. The first rule in hi-fi compatibility should be to put the system into a suitable room - one with good-enough acoustics. If we don't, we are just kidding ourselves about everything else. I know some of us aren't so fortunate to have good acoustics. The acoustics have less to do with furnishings and opulence - the room shape has much more significant influence. Unfortunately, the architects who design houses mostly don't study acoustics. Likewise, the reviewers who ensured the death of tone controls cannot have understood acoustics either! Perhaps they have the luxury of perfectly proportioned rooms? And what about the ear-designers? You know, those who dominate hi-fi thinking, yes, including Mr Forum Anonymous. Does anybody say a thing about room acoustics? I had to laugh when I saw the sheople evolution memes. No place like hi-fi illustrates it better. A tunnel cross-section room booms and a square plan room sounds dry, and the equipment always gets the blame. Equipment manufacturers, having plumped for mass production on an investment whim, must force their products on you by worrying you. Is that a bit like sheep worrying? Are you getting the picture yet? When you read that X has a crappy frequency response - perhaps it booms - maybe it sounds dry - perhaps when in an adequately dimensioned acoustic, it shouts... There is a massive market for audiophile electronic components for the simple reason that such components "highlight" what our acoustics might not give us. Think about it. Do "wema screamers" work in every setting? Does an overdose of polypropylene taste like too much sugar in your coffee? Do audiovile electrolytics turn you on? He who shouts loudest - the forum warrior - gets a following, but has he a clue? It is quite simple if your acoustics don't add up, you need tone controls. A flat response amp is a flat response amp. If it doesn't sound that way, measure your room, run it through the Amroc calculator. Stop being told sh*t by all and sundry, and get a grip. https://amcoustics.com/tools/amroc - https://amcoustics.com/tools/amroc ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 11 Feb 2021 at 9:19am
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Between my speakers, slightly offset in the wall behind, is the door from my R&D office to the junk room. It's also on my route home - to the door that leads into the kitchen, but the point here is the door between the speakers. With the door shut, my room acoustics are spot-on. However, it does feel a bit claustrophobic, and to save wearing out the hinges, I prop it open. Does it change the sound? Yes, it does! Is it a problem? No. Room acoustics can be flexible to a degree. Knowing it affects the sound a little helps me assess how the products I design should sound in any home where the acoustics are close-enough for good musical appreciation. The back office, which was initially built to audition, got built wrong. The ceiling ended up 6 inches higher, and the side walls came in a total of 4 inches due to "dot and dab." It became a boomy tunnel. There's a topic somewhere on this forum that goes into greater detail. Other factors included a concrete slab floor poured onto 4-inch insulation, which is excellent for heat insulation but amplifies boom. The other is the ceiling, which by habit, the builder hung on battens. Modern houses are often built the same way. When the reviewers finally come down off their high horses, they might consider room acoustics. Another thing reviewers don't tackle is interference - everything is so Plug'n'Play after all - what could go wrong? We have something between our ears, just behind our eyes, inside our skulls, that we don't seem able to use anymore. Once upon a time, we'd try and learn, but now if anything goes wrong, we google it and follow opinions, and Mr Forum Anonymous (he who shouteth loudest) always knows the answer. Obviously, he does because he gives us loads of links, which lead us around in ever decreasing blinded circles. "Graham, you designed X wrong because it makes an odd noise" (X being something that served thousands of users perfectly well for years, but let's not overload our simple mind). Next email: "Graham, you're not alone because I bought Y's product, and that does the same. Perhaps I need to educate you both?" "Graham, you need to look at this link, and this link, and this link, and I think you might learn something." What? After 57 years! Do you know what came next?! (in case you don't, it is a well-known phrase beginning with the letter...) ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 11 Feb 2021 at 9:31am
 Got it yet? ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 11 Feb 2021 at 10:04am
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In Marcus Graham Scroggie's day, you could explain the science without interruption and being told you are wrong. This topic will continue to explain why things are the way they are, as it started to do. To recap, I investigated the problems passive interstage phono preamplifiers have. I'd thought I'd explained it quite well. Still, it would seem you only need to make yourself into a self-appointed guru, add some hubris, and say that passive interstage phono preamplifiers are the best (because that's what you're selling), and out goes any proper discussion. (who said so? I get emails!) ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: BAK
Date Posted: 11 Feb 2021 at 3:44pm
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I say don't respond to "negative thinking" emails or comments. Stand by your electronics design experience that has always been about making the sound it produces the best it can be. As Ian says; "Just listen, if it sounds good to you, enjoy it." ------------- Bruce AT-14SA, Pickering XV-15, Hana EL, Technics SL-1600MK2, Lautus, Majestic DAC, Technics SH-8055 spectrum analyzer, Eminence Beta8A custom cabs; Proprius & Reflex M or C, Enjoy Life your way! |
Posted By: BAK
Date Posted: 11 Feb 2021 at 4:25pm
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The way to make "clicks and pops" not so noticeable is to give the 1st stage of amplification more headroom for 50% to 70% of the loudest expected "clicks and pops". (50% to 70% of the loudest expected "clicks and pops" would be those that are tolerable and not be disruptive to the audio.) The 1st stage has to negotiate the rising frequency response of the magnetic cartridge and the frequency response of RIAA shown below... At 20kHz it is 20dB louder than at 1kHz. That needs to be reduced in the 1st stage.  If the 1st stage of amplification cannot receive the higher frequencies with enough headroom, the sound will get very distorted. Graham likes to use 14dB or more headroom above the loudest expected musical peaks... This keeps the signal very far from ever "topping out" or clipping. This also reduces the noticeability of "clicks and pops". The 1st stage of amplification must have some frequency equalization for the headroom to exist. As RIAA curve shown below... (from one of Graham's designs.) the frequency response shows 40+dB gain spread from 20Hz to 20kHz.  Follow the black section of the green trace... The red trace shows where the "theoretical" headroom is. (The actual headroom may be + or - 6dB from the red trace due to real parts interactions.) At any frequency on the graph, the headroom red line is more than 14dB above the black. The phono stage needs to give the bass a boost of almost 20dB and the treble a reduction of almost 20dB, both with respect to 1kHz. A MM phono stage with a gain of 41dB would have: 41dB @ 1kHz, 61dB gain @ 20Hz, 21dB gain @ 20kHz. Adding 14dB headroom would give extra voltage above that needed to amplify those amounts. If the 1st stage is not frequency equalized, it is almost impossible to get the headroom needed. The above explanation is including knowledge gained from Graham Slee's many tutorials, but I have learned these facts presented here to be true over the past 50 years of my own experience in electronics design and maintenance. Graham, don't stop being a promoter of great sounding audio designs.
------------- Bruce AT-14SA, Pickering XV-15, Hana EL, Technics SL-1600MK2, Lautus, Majestic DAC, Technics SH-8055 spectrum analyzer, Eminence Beta8A custom cabs; Proprius & Reflex M or C, Enjoy Life your way! |
Posted By: patientot
Date Posted: 11 Feb 2021 at 7:16pm
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Bruce, I think the second graph is a particularly powerful visual tool. ------------- SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges. |
Posted By: Graham Slee
Date Posted: 12 Feb 2021 at 7:47am
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Tweeter damage is due to high-frequency clipping. Could that be true? I'm not a speaker designer. I sometimes wonder if tweeter repairs are still as common since vinyl was deprecated? The hash, the "groove burn," and the fake detail caused by high-frequency clipping - the reviewers kept gushing about the high-frequency detail, so we had to agree! Would you be from the same deceived generation, or did you never read HiFi Answers, or "The Audiophile," with heaped-praise dripping from Jimmy Hughes' pen? Don't believe me - believe your ears! The grand finale on the inner groove is where you find it. The detail is not clipping. The detail is not added cymbal shimmer. The detail is not groove burn. Groove burn happened with steel needles! Groove burn happened with two new pence headshell weights! Those records are damaged! Knowledge used to be passed down, but now it's created on the fly. I know some readers of this forum are too far gone to be taught about reality. I am not writing this for them - I'm writing it for those left. I'm not going to get into the technicalities in this post, but you'll see next time. I just wanted to finish this one with some more audiophile review-dripping from yesteryear. An incredible turntable came on the scene in 1979. Jimmy praised it as being the poor man's LP12. I've since heard both, and all I can say is that Jimmy's readers were as gullible as I first was. Unbelievably, some forums do have useful information from old codgers. One "tradesman" spilled the beans regarding the "incredible" turntable - it was designed to run fast to make it sound brighter. And brighter it did sound! Now, if audiophiles want bright, it begs the question, "is their HF hearing shot?" Maybe it also begs the question, "do they like music, or could it be for sound-effects?" Being an old hippy-music type, I was unable to get on with bright. Take "Gates of Delerium" by Yes, for example. When the Gram Amps got famous, I'd spend an hour on the phone with each customer, and they lived in fear of brightness. They begged me to be honest about the Gram Amp not being bright before they'd part with their money. I understood from those conversations that audiophilia was not as popular as Jimmy perhaps wanted his movement to be. Most customers want fulsome music. I hope you are who I'm still working for. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 12 Feb 2021 at 9:29am
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Hey! Great find, Bruce! Excuse me for flipping the image. That bendy curve is just what I was looking for.  Rather than bend your head upside down, note the 1kHz position from Bruce's post, and now note that at 20kHz, the signal is 20dB (ten-times) bigger. Should you buy a passive phono with a 20dB clip margin at 1kHz, it has no margin at 20kHz. At 20kHz, it has plenty of distortion, however. Near clipping, distortion increases rapidly. Perhaps it would need to come down a bit? The best headroom we got for the BBC radio desks was 26dB (but they never played vinyl on them). I know we'd have had to go for discrete circuitry to get more, as with op-amps, the power supply was a maximum of 36 volts. Now, on that inner groove, the nips and tucks are tighter, and the excursions need to be larger to keep the same relative level. The best of styli do break rank just a little, and so the highs might-well get a tad higher because this is where the mechanical distortion is at its worst. If there's no clip margin, the distortion is 100% where the stylus breaks rank, so you'll need at least 26dB, which requires a 200mV max input! But what about the hairline scratch? What about the micro-bubbles due to stamping a hot dollop of vinyl? If those bend the cantilever that tiny bit further, the output increases. When that input stage clips, negative feedback ceases to work, and the gain zooms up to its open-loop value. That compounds the click - it lengthens it. What would have gone unnoticed because of its equivalent high-frequency is now reduced in frequency because its effect is extended in time. To prevent that happening requires a lot more input latitude than 200mV, requiring a high voltage power supply of 90 volts or higher. I think Technics used 126 volts on a phono preamp (I'd have to check). Now, if you go to Audio Science Review, you'll see they understand what I've said above, but they have no understanding of active EQ. The clip margin on active EQ follows the curve, so if it's quoted as 46mV at 1kHz, you multiply it by 10 to get the clip margin at 20kHz - which is 460mV. To get a 460mV clip margin out of a passive either requires a massive supply voltage or much-reduced input stage gain. The latter is a no-no for the signal to noise. What helps the passive, however, is its RIAA filter. Being passive (as per its description), it applies the equivalent of a scratch filter, which rounds off the clip's sharp edges. It is the same method used in synthesizing a sine wave from a square wave in hardware circuitry, except it only has one stage of filtering, so it isn't fully disguised. However, it does add hash, or as the audiophile reviewers called it - detail. Rather than boldly saying that active is better, I won't. It is better only if the circuit can do what the theory says. The theory states that the clip margin increases with frequency, and it does so because the negative feedback is the EQ. The problem here is overshoot, which is down to timing, and timing is down to propagation, but you'd only understand propagation if you did logic, which most audio dabblers haven't. The result was that active stages clipped like crazy and emphasized clicks and pops. They were the cheap afterthoughts included in stereo amps, and they got vinyl a bad name. So, based on that, yes, the passive stage is better - I'll give them that -, and I should know because I've built plenty. However, if you did a lifetime's research into active's and can work around the propagation delays using the brain rather than the bullsh*t, you can speed it all up and beat the passive into the ground. The icing on the cake - the ultimate in resolving all these issues - came from an observation of the "uptick" you can see at the bass end of the upsidedown image. I first observed that as a youth playing with ceramic cartridges. The result was the Accession, and why I spent so much in patent fees to make it mine. The point I try so hard to make is the technology has to be appropriate! You can't go around claiming God-like prowess because you'll come undone one day. As the Prophet, Daniel spoke, "many shall run to and fro, and knowledge shall be increased." But he also said, "How long shall it be to the end of these wonders?" ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Sylvain
Date Posted: 12 Feb 2021 at 9:54am
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''....What helps the passive, however, is its RIAA filter. Being passive (as per its description), it applies the equivalent of a scratch filter, which rounds off the clip's sharp edges. It is the same method used in synthesizing a sine wave from a square wave in hardware circuitry, except it only has one stage of filtering, so it isn't fully disguised.....'' My 2018 DAC seeks a premium to replicate RIAA equalisation filter to reproduce a more natural Tone from 24bit Digital files
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Posted By: Graham Slee
Date Posted: 12 Feb 2021 at 10:46am
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No, your DAC requires a proper analogue filter. Unfortunately a smashed vase reassembled using super glue always looks smashed.
------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 12 Feb 2021 at 1:06pm
The Art of Electronics, 2nd Edition, is available here https://www.academia.edu/23116033/The_Art_Of_Electronics_2nd_Edition - https://www.academia.edu/23116033/The_Art_Of_Electronics_2nd_Edition Section 7.07 onwards talks about amplifier output errors, and those errors apply as much to phono stages as they do to DAC analogue output filters. The datasheets from the DAC chip manufacturers ignore it because it would not achieve 120dB S/N. The errors only apply to music reproduction, so a specification viewpoint is immaterial. Poorly qualified people generally staff the media. They might understand specifications, but nothing as advanced as the amplifier errors described in 7.07. If they did, they'd not be writing the way they do. By sacrificing noise you'll never hear, such errors are pushed out of the way. I knowingly publish the Majestic coax and optical input spec as 102 to 103 dB S/N, which is honest. Naturally, on seeing this, most avoid the Majestic like the plague. More fool them! ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: patientot
Date Posted: 12 Feb 2021 at 5:27pm
Wow, this certainly puts things in perspective. :)
I think this explains why your design has stayed in my system and all others got dumped. :) ------------- SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges. |
Posted By: patientot
Date Posted: 12 Feb 2021 at 5:42pm
Audiophilia is full of buzzwords. "Detail", "warmth", "air", etc. from what I've seen. Rarely do you see people using the word neutral. I think a lot of people must like a highly colored sound, rather than listening to what's on their recordings. Maybe they have been trained to like that colored sound by the mags, writers, influencers, and the echo chamber you see on audiophile forums and the like. RE: hearing, people never want to admit it, but as we get older, our ability to hear those high frequencies diminishes. I cannot hear as well as a teenager or twenty year old person, it's simply not possible. Awhile ago I was reading a review of a fairly expensive cartridge out of curiosity. The reviewer said in his commentary that the cartridge was very neutral and presented what was on the record. The lab test report at the end of the review told a different story. A significant treble boost around ~10kHz and above. To me, that cartridge would've sounded very bright and boosted and harsh in an unpleasant way. I don't think the reviewer was lying necessarily, but I do think he probably couldn't hear much above ~10kHz necessarily. I see this type of thing all the time with speakers and the like too. One big "audio guru" personality was praising a set of new speakers like no other. A bit later I happened to be in a shop that had those speakers, or a model very similar to them, set up for demo. I listened and they sounded like icepicks going into my ears with severely boosted treble. I don't want my speakers to sound like a thick wool blanket was thrown over them but I don't want that either. ------------- SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges. |
Posted By: Graham Slee
Date Posted: 14 Feb 2021 at 5:46am
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When the disappearing trick stops working Click and pop removal, the way I do it, is an illusion like some magical trick. There is no click and pop filter. I do not remove clicks and pops, and if everything goes to plan, you won't hear much of them. The conjurer uses speed and a decoy. The decoy here is you being drawn by the music, and while you are, the clicks and pops are quietly and quickly ushered through. That's all there is to it, and you'd know no difference, but then Dick Bastardly came along in the form of wannabe amplifiers, preamplifiers, and boutique cables. A shiver ran down my spine. Suddenly, Otalas' gift was trodden underfoot, and with it, Olivers' criteria and the audio matching system (to name a few). Everything I had held so dear - it all followed each other down the lavvy. I developed cables and a headphone amplifier to stem the flood, through which the illusion could be preserved. Still, I desperately needed a preamplifier and a power amplifier to get my phono stage people fully Slee'd. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Sylvain
Date Posted: 14 Feb 2021 at 12:56pm
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...''There is no click and pop filter. I do not remove clicks and pops, and if everything goes to plan, you won't hear much of them....' the audio matching system (to name a few). Everything I had held so dear - it all followed each other down the lavvy.'''' Humnnn and Not just electrical |
Posted By: Graham Slee
Date Posted: 14 Feb 2021 at 7:15pm
 These graphs show (300) the output of the cartridge versus frequency, (302) the record's frequency response, and (304) the combined output of the cartridge playing the record.  This is a typical active phono preamp by Walt Jung. The network R1,2,3 and C1, C2 applies frequency-dependent negative feedback.  The curve illustrates the resultant frequency response (400) within an amplifier's open-loop curve (A, in Jung's diagram). The network can be simplified to (500), where C2 represents C1,2. The gain is decided by the impedance of the network, divided by R2. Because all signals average as symmetrical, the positive and negative excursions must be identical (but opposed). Positive and negative excursions drive C2, and at frequencies mainly in the middle "kink" of the curve, C2 charges first one way, then the other. The ideal drive is an opamp with symmetrical signal output swing. Its positive and negative slew-rates must match. Slew rate is volts per time, V/T, and as the charge formula is CV = IT, then V/T = I/C = slew rate. C2 (in 500) is the parallel value of C1,2 in the Jung circuit, and his values make 7.5nF. A common opamp for this work is the NE5532. It can output 16mA, and 16mA/7.5nF = 2.13V/uS. The opamp can do 9V/uS, so the network loads the opamp at high frequencies. However, the opamp can drive 600 ohms, and if R2 (500) were 600 ohms, it wouldn't matter much, but R2 has to be smaller than 600 ohms for sufficient voltage gain, and in Jung's circuit, it is shown as 100 ohms (R3). The opamp is still heavily loaded at high frequencies. Some might argue 2.13V/uS is sufficient for all audio frequencies with an adequate margin. With capacitive loading, the cartridge output peaks then starts to fall in the 10kHz - 20kHz region. The operative word above is "peaks," in that the cartridge inductance forms a tank circuit with the capacitive load, damped by the input resistance (47k). There are surface defects, cutting resonance, fast transients, recording overshoot, distorted de-essing, arm vibrations, cantilever vibration artifacts, instrumental and vocal one-sidedness. As we have seen, cartridge amplitude changes with frequency. Add all this together with series inductances of all the wiring. Could there be a chance that a faster slew rate might better accommodate these things? I think so. Therefore, the balance between the output current and capacitive load of the EQ network must be adjusted to increase the slew rate. The next part will deal with input slew rate. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 14 Feb 2021 at 9:07pm
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Refering to Art of Electronics 7.07, we find input slew-rate depends on how much voltage swing the input can take before its overload must be passed to the next stage. The next stage must feature compensation to rid excess phase which would result in instability. Once input overload is exceeded the input drives the compensation capacitor, and so there is a step change between the intended input impedance and the lower impedance of the next stage in parallel with the capacitive load. A silicon transistor has a 60mV peak linear "portion" and should the input stage be differential, which it is in the case of an opamp, the maximum rms voltage is 42mV. This can be agued away by saying that negative feedback increases the input latitude, but if it is assumed the negative feedback has failed to function in time due to propagation delays, then the 42mV stands. If the cartridge outputs 4.2mV at 1kHz, it is 42mV at 20kHz. There is no headroom. Section 7.07 also derives an input stage slew rate formula, which is 0.3 x Ft, and using a common low noise opamp for phono stage use, the AD797, we find it's stable Ft is 30MHz. It's input slew rate must therefore be 0.3 x 30 = 9V/uS. It is advertised as 20V/uS, but that is its output slew rate. It is obvious therefore that it has slew rate enhancement, and that never sounds good, because to do it, the input stage must clip. The low noise ability of the AD797 is hampered by the requirement of an input resistor to prevent instability. Here are the datasheet takeaways.  The internal circuit shows the input stage emitters joined together supporting the 42mV finding.  The Open-Loop Gain and Phase Margin vs. Frequency graph shows the double kink of the phase response which illustrates the change from input slew rate to output slew rate. This is coupled with the expected "dive" in fall off rate from 1MHz to approx. 3MHz (the difference between 20V/uS and 9V/uS). It also shows that Rs* must be used or the phase margin shrinks to less than unity.  The resistor Rs* adds input noise above the claimed 0.9nV by square root of frequency range. 1k adds 4nV. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 14 Feb 2021 at 10:15pm
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If we look at the NE5532 op-amp datasheet, we can see similarities with the AD797. The declared slew rate is 9V/uS but using 0.3Ft, we find its input slew rate is 3V/uS. We can also see a similar change of roll-off rate by looking at figures 2 and 3 graphs. https://www.onsemi.com/pub/Collateral/NE5532-D.PDF - https://www.onsemi.com/pub/Collateral/NE5532-D.PDF We can still use it for a phono stage provided we adjust C2 (earlier post) and taking 16mA/3V/uS = 5.33nF. The parallel values of the EQ filter capacitors must not exceed 5.33nF. The ratio between the two capacitors is typically 3:1, and so we might choose 15nF and 4.7nF, which will give us the equivalent of 3.7nF. In doing so, we have some output current left to drive whatever the phono stage connects to and its interconnect's capacitance. We still have the input overload problem of 42mV because of the joined input stage emitters, so we must ensure the signal gets fed back without much delay. It has helped by keeping the input slew rate up. We should choose some stacked film capacitors - not wound ones - because we don't want to add series inductance. By doing the above, you will get a good way towards minimizing clicks and pops, and at the same time, it should beat quite a few other phono stages on musicality. There is, however, one slight problem, and that is the positive and negative output slew rates will differ. Very little is shown on the datasheet. It is an old design from 1976, and I suppose the manufacturers want to keep selling them and don't want bad publicity. The only way of telling that the pos and neg slew rates will be different is to examine the output stage. If you follow the horizontal diode to its cathode, you will see it joins to a transistors' collector. If you follow the diode's anode end through the "emitter resistors," you will see it joins to a transistors' emitter. It is a quasi-complimentary output stage, with a Shaw helper diode (the one you just followed). TI shows a Baxendall transistor in this position. The On-Semi and TI versions sound different. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: patientot
Date Posted: 14 Feb 2021 at 10:34pm
Interesting stuff. There is a DIY design making the rounds for awhile now using the AD797. Some tests show noise is very low but I wonder about the disadvantages and there they are. Might look good on paper with low noise specs but all records have noise and will never be able to meet those S/N and THD specs anyway AFAIK. ------------- SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges. |
Posted By: Graham Slee
Date Posted: 15 Feb 2021 at 10:39am
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Working freelance for a couple of years with a hi-fi manufacturer after the radio broadcast audio disciplines, I saw the tendency to dabble in the "exotic." Today I call it virtue signaling, a kind of Twitteresque "look at me - look at what I'm using!" If the pins are in the right place, you can just about get away with plugging-in any op-amp, and it'll make some sound. The way I see forum op-amp choice is about the op-amp's ability to sock it to them. It reminds me of the dawn of colour TV and the migraine headaches from watching such exaggerated colour - the colours turned up full. It's where Hi-Fi departs from high fidelity, but Hi-Fi trips off the tongue - simpleton language - but I use it to try and attract and convert the lost. Like setting the colours on a colour TV to something more natural, and then making it more real. Input slew-rate is the reality. Output slew-rate exceeding input slew-rate is artificial, and an enhancement originally meant for large-signal analogue processing, not in high fidelity audio! But, if the market's there, exploit it, and it would seem that the chip manufacturers added the "message" to their datasheets. It is hysterisis. Push the switch so far, and the spring snaps it into place. It's seen in the bode plots, where the single-pole stability is traded to push the open-loop gain at the expense of overshoot but then revert to bringing it to unity with just enough phase margin to spare. The technique is called "feedforward," where the single stability pole is delayed. Excess phase comes in while the amp still has gain (40dB on the 797), falling nearer to 40dB per decade than the stability assured 20dB per decade. Then, just before complete instability ensues, late compensation gets applied to prevent it "crash landing." The 797 phase plot makes it obvious - the phase recovers and kicks out before falling away again. The bend in the gain plot coincides. What more do these people need? I think the answer is they didn't go that far and just read the headlines. I cover a similar application in my '70s amp ramblings. It can have good use in bringing down high-frequency THD because there's more negative feedback available, but at what cost? One cost is ringing and with it, harshness. The NE5532 (and similar versions) has this "guilt," but to a lesser degree. If we want high fidelity, we should stick to physics's applicable laws and work inside them. It means understanding what we're working with, rather than just plucking some half-baked idea and trying to persuade everybody Dylan fashion. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 16 Feb 2021 at 7:50am
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The only way to increase the slew-rate is at the input. I can see how the CD-era "designer" could have thought - anything above 20kHz is inaudible - but the highs in analogue aren't the noise dumping-ground as in the red book. Screw around with analogue HF, and it will bite you! God forbid, but if we ever ended up in a Soviet system, I'd hope the authorities make them design discrete power amplifiers before allowing them near op-amps. The op-amp is a power amp in miniature. Do with a power-amp what I see done with op-amps, and you don't even get a chance of it living past switch-on! Dry sound? Are your power supply caps getting warm? What's next - Blackgates? What you have to dig, brother is bandwidth with single-pole compensation, respect stability, and that 0.3Ft is all you're ever going to get in a low-noise world. The AD797, like the LM318, and all that follow in their footsteps, thought up cunning ways to take noise down and pump-up slew-rate. You might be under the mistaken impression that these ICs only live under the hoods of phono stages and headphone amps - think again! They're used everywhere the opportunist manufacturer wants - I mean, look, man, it's so low noise! Screw low noise! Stop crippling music! Taking 0.3Ft, it begs a multiplier to give a larger result. How about if we added "m" to make it 0.3mFt? Where can we find "m"? "m" can only exist if the linear portion of input latitude is increased. The joined emitters limit us to 42mV. What if we could make that 420mV? "m" would be 10. If we take what can be achieved by single-pole compensation, say, a bandwidth of 4MHz, the 0.3Ft slew-rate is 0.3 x 4 = 1.2V/uS. Multiplied by an "m" of 10, we obtain 12V/uS. And if multiplied by 20, we get 24V/uS. Isn't that great? It's done by placing a resistor in each emitter leg such that the gm of the stage gets reduced by the value of "m." It has downsides - one being that open-loop gain has been reduced (you won't get as much negative feedback). The other is that noise increases. The reason that noise increases is because resistors "contain" noise at the rate of 4nV per /Hz per 1,000 ohms. However, it has another benefit, not requiring such a considerable value of compensation capacitance. Therefore, if the input signal strays even further than the x10 or x20 we gave it, the overload has a much gentler time. The technique is called "emitter degeneration." ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 16 Feb 2021 at 3:04pm
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Before moving on from the "low-noise wide-bandwidth" op-amps, just a bit more enlightenment regarding the NE5532 (which has a startling resemblance to a NE5534, but the NE5533 is its dual version). Below is the dead giveaway.  A stable single-pole does not roll-off from 1kHz to 10MHz in 100dB. It either rolls-of from 100Hz to 10MHz or from 1kHz to 100MHz. 20dB/decade is 100dB/5 decades, and 5 decades up from 1kHz is 100MHz. The only way it can go from 1kHz to 10MHz is by putting in a steeper step, just like the AD797. The above images (figure 2) from the NE5532 datasheet makes it look like somebody was trying to cheat. Figure 3 is effectively the same graph, and if printed-off and annotated with pencil and ruler, sketching through the curve ends, you should find a very similar gain "bode" curve to the AD797. The significant difference is in the Ft - the frequency which transitions unity gain (0dB). The NE5532 does it gracefully, but the AD797 needs Rs* doctoring. The difference is stability and brought stable by Rs*; the AD797 is no better on noise than a NE5532. The signal does not cause instability. There won't be any signal at 10MHz or anywhere near. There is, however, stimulus, and always will be, unless switched off. The unstable op-amp can be triggered into oscillation by just about anything. Oscillators make their own signals! It is no wonder that a NE5532 can make a good phono stage, provided its real slew-rate is used to calculate its active EQ capacitance. Now, what phono stage could that have been? ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 17 Feb 2021 at 3:20am
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The big problem with active stages revolves around misunderstanding slew-rate and output current. Most op-amps oscillate into little more than 100pF and need in-loop or out-of-loop output series resistance. Often you'll see the op-amp driving the EQ capacitors directly. The divider resistor to ground from the feedback pin might be seen as the equivalent of this series resistance, but the phase is different at that end. The craze for zero output resistance in op-amps for headphone amps might now look a bit stupid? Headphone cables might have up to 600pF of capacitance. Those people are "enjoying" high-frequency instability, in which case, op-amp "rolling" gives a different type of instability. One type of op-amp which can withstand capacitive loads is the bootstrapped output stage type. This type of bootstrap is nothing like the "pull-up" bootstrap of an ac-coupled power amp. It senses load capacitance and reduces bandwidth to bring it back into stable operation. It is a kind of frequency compensation, but outside the gain stage. However, that in itself cannot prevent oscillation. Still, to avoid using a "Miller" capacitor in the VAS stage, it uses emitter degeneration to reduce the excess phase contribution by the input stage.  The slew-rate is a staggering 350V/uS. By 0.3Ft, with a bandwidth of 50MHz, it should be only 15V/uS but is 23 times higher due to the emitter degeneration resistors' size. It tends to suggest that the input can take 1 volt before overload. That is the voltage often found in video, and that's what the op-amp is designed for. However, it is an op-amp, so that it will work down to DC, and as such, it works for audio frequencies. What size of "C2" can it drive? With 50mA output current and by I/SR, we obtain 143pF. That is a shame, but if we can add sufficient output series resistance, we could get it to work. Placing nearly 1k in series with the high-frequency pole capacitor, it "flys" if we can accept that the RIAA curve isn't necessary at, say, 50kHz. It was used in the original Era Gold, which might give you a clue as to how it sounds. Although the S/N was acceptable to the ear, it wasn't acceptable on paper and turned quite a few prospective customers away. I'm sure I'd still be using it to this day if it didn't have a popcorn-noise problem. Each device was tested by AD for its purpose as a video amp, and at such frequencies, that noise is not apparent. We had 50% fails-on-test, and to continue making the Era Gold and Jazz Club, I had to redesign it in a way that didn't change the sound. To do that, you have to understand op-amps. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 17 Feb 2021 at 9:52am
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Taking another look at the AD826 (AD817) schematic, the differential VAS and complementing Wilson mirrors have no capacitive compensation. Transistor capacitance is due to base width, and therefore, the VAS, if not the IPS, must have had relatively narrow bases. Any process contamination and popcorn noise would be inevitable.
------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 18 Feb 2021 at 1:23am
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Rant Warning! Did you watch Tim Peake's mission to the ISS? When it came to docking, it looked like there was a problem, then on flicked the coloured bars on the TV screen. A few moments later, the picture came back, showing the astronauts entering the ISS. What you didn't see, is what's known as a "proprietary moment." To the outsider audio can be a bit like that. Let me rephrase that - to an outsider with a serious desire to learn, audio can be a bit like that. Everything can look oh so snobbish, but out of sight, something rather vulgar might be going on. A good example is the preamp of a dynamic mic. Oh yes you know, it's phantom powered, such a fine method of placing a DC voltage on the balanced inputs - just look at the network - look at the high tech... Tucked away in the mic body is a single transistor preamp (or used to be). What? Trust that quality of signal to such a horrible-horrible single transistor. Don't they know such-and-such superstar will be using the mic? By now, possibly a handful of old timers who visit my posts (hi friends!), will be getting the gist. Others might be thinking of sending me their nephew's college textbooks on how to design basic audio circuitry - it has happened - such people are beyond salvation but are easily offended by the Yorkshire pit language reply! "How can it be that Yorkie's can learn things - surely all Northerners are dumb?" Well, dear bigot, that might be why it took me 57 years to learn what I know. End of rant. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 18 Feb 2021 at 3:15am
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So far, I've talked about phono stages and the different approaches. 1. The "afterthought" in a cheap amp (it'll be active!) 2. The "bandwagon" interstage passive (faults as described) 3. The fast-active (very rare) The "afterthought" is just about guaranteed to obliterate the music in favor of record surface noise. The "bandwagon" is something that I've built on multiple occasions and has its own built-in partial "scratch filter." The fast-active passes the lot without modifying the scratches, clicks, pops, or music. If the rest of the system was equally-well designed, then it's doubtful you will hear the scratches, clicks, and pops because the music dominates. But what happens if the rest of the system was NOT equally-well designed? And how can that happen? Early on in the 1970s, Matti Otala was tasked with investigating why amplifiers could sound bad. Philips recruited him from university. He later wrote a paper on it for the AES (1972). I don't remember anything about it in Britain at the time, and I'd only heard of the basic gist, but it was sufficient for me to understand the prerequisites of fast-active design. The batten was also taken-up by Walt Jung and associates in the American "Audio" recreational magazine. In several editions, Jung went straight over the reader's heads in explaining what made amplifiers corrupt the signal. Again, such things never featured in any of the British technical press, and so it was a matter of piecing together the imaginations in my head and hoping I'd got it right. It has only been the last 22 years since the Internet has made it possible to visit "other worlds," and with thanks to those who archived such works, the British designer (me?) has been able to connect-up the missing pieces. It was with great relief that I learned I'd been on the right road and had now found a wealth of techniques to further my interest in better audio. Most British designers were of fine reputation and had done their best in "blindfolded" Britain. Those with access to American information were making better amps. Douglas Self had been our only connection with the professional design world, and John Linsley Hood had also done his best. By the early 80s, Paul Miller had started testing high-frequency amplifier performance. With his listening panel, he could mate-up the listener's reports with the technical test data. He found that amplifiers having poor high-frequency control sounded spitty and noisy. With all the above information, I was able to rate my chances of making fast-active phono stages. I knew the ones I sold to owners of "sensible" amplifiers would be the winners. I became highly suspicious of hi-fi bullsh*t. I knew the market would never be massive but also realised that I would never compete big-time as a one-man-band. The above knowledge served me well in developing a headphone amplifier. The Solo has changed little in its 20-year history. Auditioning using vinyl records, if hearing harshness, clicks, and pops, I knew the design was wrong, and I must try harder. Again, the Proprius, the lack of harshness clicks, and pops told me the product would be acceptable. It has significantly helped in the development of the proposed DAK kit amplifier. It always highlights stability problems and enables me to troubleshoot a circuit. Even though I do a lot of auditioning using digital files (for convenience), I could not imagine developing highly musical line-level and power amplifiers without the transparency of the fast-active vinyl source. I started writing this topic because it would seem new people are joining us, hoping to solve their vinyl issues, but without much, if any, understanding of the systems they've chosen. Some of the vast mid-market amplifiers' choices are being equipped with whistles and bells, often featuring microprocessors and logic chips to select sources. To me, this is a backward step that can only result in some form of uneducated revolt against the electronics art my career holds so dear. The loaner program might now be a bad idea. I liken it to the misfortune of Eddie Hall, always being challenged to a fight each time he walks out of his front door. With the flood or dumping of - dare I say it - highly technological looking amplifiers from China - subsidised by the Chinese Communist Party (HMRC is watching), which are little more than convenience electronics made to look hi-fi, it is only a matter of time before the conjurers trick (the one I mentioned earlier in this topic) stops working. This conjurer's trick of fast-active circuitry is one I stand up for because, in effect, it isn't a trick - that's my sense of humour: the no-cheating method of preserving the vinyl signal such that it may be passed on by equally fast, carefully considered circuitry to obtain almost faultless vinyl reproduction. Next time I hope to discuss the difficulties and solutions required for the smallest of signals ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 18 Feb 2021 at 11:57am
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High frequency power supply Although it cannot exist in wire or cables, because it cannot be scientifically proven to the satisfaction of a university lecturer, turned cancel-culture troll, who the uneducated government ASA department believed - high-frequency noise paths have existed in printed circuits - which are "printed wires." Being bullied by the courts, waving-about possible fines for disobedience, I decided my financial situation was more critical. Are boards full of chips accompanied by 0.1uF ceramic capacitors for no apparent reason? I often wonder about detractors' legality using uneducated government departments to leg-down British industry, but being small-fry, I have no voice. However, I do here, and I will continue to belittle those who disrespect physics laws and hopefully do my bit to prevent the British establishment from returning to Babylon. It is a long path from and back to the power supply for high-frequency signals. You might prefer to think of the printed circuit traces as like the spring in a spring line reverb. It is probably one of the best analogies I can make. A drawing of a spring looks like the symbol used for an inductor. PCB tracks, at high frequencies, become inductive. They might be thought of as a solid rod at DC and audio frequencies, but that rod gradually morphs into a spring with increasing frequency. Now, if you would like to picture an old computer board, you would see one 0.1uF ceramic capacitor near each chip. These cancel the effect of the spring reverb. When a chip rapidly switches a function, it would resonate down the spring line and modulate the other chips voltages. With old TTL, a switching action consumed sufficient current that without a 0.1uF "cancel" capacitor, the glitch often did cause other chips to switch falsely. The small duration charge on the 0.1uF capacitor was sufficient to supply the chip's power for the switching step's finite time. It was small-enough to recharge instantly to absorb the next action, and therefore the 0.1uF capacitor IS the high-frequency power supply. An alternative explanation can be found here: https://en.wikipedia.org/wiki/Decoupling_capacitor#Transient_load_decoupling - https://en.wikipedia.org/wiki/Decoupling_capacitor#Transient_load_decoupling ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 18 Feb 2021 at 2:17pm
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What's worrying in a world full of misinformation is that the truth can be easily trashed, especially if not supported by the crowd. You must accept that audio signals have nothing at all in common with high-frequency signals, or that is what is expected of you. It serves a purpose, but a very dishonest one. Musical hearing is in the musician's dominion, as if by special decree. The audio design engineer can only have a musical hearing if also a musician. I cannot read or play music, and the less said about my singing voice, the better. However, if I wire the ground connections of op-amps to a "ground mecca" on a printed circuit board where the path is already catered for by a solid ground-plane and say I can hear the difference it makes, I am lumped with the lunatic fringe. I insist the grounds are wired in such a way on every Accession MC, but I don't on an Accession MM. It isn't that the two use a different kind of electricity; it is because my senses cannot detect any difference once past an order of magnitude. Measurement techniques coupled with the prescribed notion of how things work have limited the test engineer to measuring the stuff of Harold Black's day. They are mostly 100 years out of date! Opinions - many imaginary - have multiplied, while measurement technology has stagnated. It is not that some of these phenomena are fanciful - world governments dictate that EMC must be proven, don't they? The stagnating measurement gurus, on whose equipment we produce product specifications, is so outdated that the ultimate proof of a product's compliance can only occur in a government-approved compliance lab! Come on, guys, surely you can do better than that? ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: patientot
Date Posted: 18 Feb 2021 at 6:30pm
At some point I will be shopping for a new amp to replace my current integrated amp. It will probably be awhile before I can get the new amp but I do look at what's on the market from time to time. The big trend I am noticing is multiple digital inputs and many features I will not use because I prefer separate components for those things or don't need them. Sometimes "basic" features like tone controls and REC output are also left out. I also wonder how those bells and whistles affect long-term product reliability. It makes me think of the "mini" system with combined CD changer/cassette/radio I had back in college. Lots of features but poor reliability after a year or two when things started breaking down. ------------- SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges. |
Posted By: Graham Slee
Date Posted: 21 Feb 2021 at 5:34am
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References are usually included at the end of every scholarly article. I would dearly love to substantiate my recent posts with a revealing research article from an old Wireless World issue, but Big-Tech, in the form of Mozilla Firefox, deleted it. It is comprehensive at removing all you wanted to keep, including its browsing history! If I were a budding researcher, I would seriously avoid Firefox! So why do I use it? I use it for its web developer tools. There is substantiated proof that A capacitor has resistance and inductance. A resistor has capacitance and inductance. An inductor has resistance and capacitance. A wire has inductance. A PCB trace has inductance. The scholarly article I wanted to feature here plainly shows that most wire and PCB trace sizes used have an inductance of 20nH per inch. Although audio frequencies may be classed as DC, in that such small values change absolutely nothing, what they do is act on radio frequencies. Radiofrequency interference is insidious, and the active components used to make an audio circuit are very capable of working at radio frequencies. Now, if you're unsure of that, you need to look at plenty of op-amp bode plots and plenty of power amplifier bode plots. The transition frequencies are also quoted in the tabulated sections of datasheets. Capacitors are placed across circuits to attenuate radio frequencies, but lead length places inductance in series near to transition frequencies. The sum between capacitance and inductance often cancels the effect of the capacitance. A capacitor used to stabilise a circuit can therefore be rendered useless. The answer has been to use leadless capacitors as used in surface mount construction. Unfortunately, the printed circuit traces then take the place of the missing leads. Chips in digital logic are often pinned to reduce the need for long printed circuit traces, and in some cases, op-amps have featured optimised pinning to reduce inductive trace lengths. If an op-amp "takes off" (becomes unstable) due to radio frequency interference (which is at an all-time maximum right now), then it will not perform a proper function at audio frequencies. There will be very high-frequency modulation on the audio signal waveform. Still, we have detractors who will say the audio is still audio, often pointing at multiplexing as their proof. Even if the oscillations do not change the audio signal, they affect the power supply because they all use electrolytic capacitors to some degree for energy storage. The capacitance alone is not the problem. The inductance is the problem. The foils are bifilar-like wound, and it is therefore claimed that the only inductance an electrolytic capacitor contains is due to its lead length. In that case, a radial 1000uF electrolytic should be purely capacitive well-up into the MHz. Unfortunately, it isn't, and somebody is a bit economical with the truth. To prove otherwise, you'd need a signal generator, 'scope, and a suitably sized resistor. Electrolytic capacitors cannot do high frequencies! Electrolytic power supply capacitors get hot when the circuit they supply oscillates - where the output swings to each supply polarity. That indicates resistance, and the resistance can only come from inductance. The above explains why localised decoupling is used and becomes the power supply at high frequencies. What usually causes an audio amplifier to oscillate, which would otherwise be stable, is its power supply. Therefore, a power supply is not just a black-box you wire to a circuit - it is present inside the circuit too - or needs to be. The takeaway from this post is not that audio circuits go high-enough in frequency to be influenced by inductance, but that stimulus due to RF encroachment, or an unstable active device, can, and will, make the power supply under-perform. When storage devices get hot (or warmer than they should), they do not work correctly and ultimately fail. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 21 Feb 2021 at 6:31am
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In-band artifacts Distortion cannot be denied. If you have a computer audio player with a proper "visualisation oscilloscope," you will see non-sinusoidal waveforms. Sometimes they are very one-sided, and that one sided-ness swaps polarity with pitch. If we could crunch the numbers, we might find that a particular note has its wave-shape due to harmonics. Music is harmonics. Notes on instruments are harmonic and harmonise with other notes, so do voices! Could it be possible that some harmonics are beyond our hearing capabilities? Knowing that square-waves can be broken down to a sinusoidal fundamental, accompanied with every odd harmonic, it is conceivable. The weird thing is that we can differentiate between instruments and voices because of their harmonic content, even though that harmonic content would seem to be far beyond our hearing range. Some are beyond our hearing range. I shall now quote Keith Armstrong, a recognised EMC expert: "In-band intermodulation products are inevitable when there are two or more frequencies (which there always are) and any non-linearities (which there always are). Interestingly, noise with fundamental frequencies that are outside the audio range ... can intermodulate with audio harmonic distortion products that are above the audio range, causing in-band noises to arise. The thing with intermodulation 'artefacts' is that they are completely alien to the original waveforms, so even small amounts may sound objectionable even though similar amounts of harmonic distortion products might sound acceptably low." In other words, the sound we hear can differ from one product to another because of distortion. It is rather unfortunate but commonplace that distortion increases with frequency. And this happens because of transition frequency, where an amplifier cannot amplify anymore because it cannot slew voltage fast enough. Most amplifiers are distortion specified at 1kHz. A "pattern-part" differential IPS amplifier (just like the equivalent circuit of an op-amp) has rising distortion simply because the stabilisation network brings down the high frequencies to unity gain before it runs out of phase margin. As frequency increases, open-loop gain reduces, and so negative feedback also decreases, and with it, its distortion reducing capability. Therefore, distortion increases with frequency. It is typically 4 to 5 times greater at 10kHz, and 8 to 10 times greater at 20kHz. Although your hearing becomes less sensitive with increasing frequency, the distortion can be heard as artifacts at frequencies you can easily hear. This is due to intermodulation with harmonic distortion. Just about every human being who has ever stood on a busy street with a traffic queue has heard different internal combustion engines' beat frequencies. What "falls out" is multiple lower frequencies. Radio broadcasting could not exist if not for this phenomenon. By mixing one frequency with another, transmission frequencies above human hearing are brought down to become audible. If there were no distortion, then there could be nothing in the way of the music. All music would sound the same on all products - except it doesn't. And now, if we step back and look at things like instability, which obviously cannot be heard on its own, and we add distortion to that - which will always exist - then the detractor looks a little stupid. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 22 Feb 2021 at 10:08am
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A stroke of genius? Like I said earlier, we didn't get American magazines. It was news to me that Mr. Vereker's power amplifier was 'intentionally narrow-band,' as its component values tell the opposite story! The design does the utmost to prevent output stage oscillation, and the base stoppers are as discussed in the 70s amplifier topic. Some power amplifiers need them, while other designs might not. I can't say the same for all amplifiers, though. If an output stage is prone to spurious oscillation, or the margin for stability isn't as good as it should be, then a fast transient can result in small repetitive moments of chaos. If our source is vinyl, and even the best records have surface/groove imperfections, moments of chaos resulted in exaggeration - we hear a louder click or pop than the real amplitude of that click or pop. In the sixties, the 'silicon rush' was seen as a cow for milking, and non-technical entrepreneurs soon discovered they too could make amplifiers. All it needed was an 'early chip type module,' and Japanese industry was quick to oblige. Whether the modules were inherently unstable or the entrepreneurs were ignorant about how to implement them is moot. The fact that they 'smoked' if the user accidentally unplugged a speaker betrays instability. I speak from personal experience - these amplifiers reproduced clicks and pops far better than the music! It must have been very annoying to proper amplifier manufacturers, having to compete with such upstarts. If they'd known, they might have been able to use my argument here, trounced them, and made vinyl so listenable that CD would have had a hard time competing. It wasn't to be. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Sylvain
Date Posted: 22 Feb 2021 at 8:51pm
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A capacitor has resistance and inductance. A resistor has capacitance and inductance. An inductor has resistance and capacitance. A wire has inductance. A PCB trace has inductance. I peruse your post diligently and regularly and without the technical ability or test equipment I can concur with the rationale of your deliberations clearly and intelligently though emotionally exposed but good education .....and also useful knowledge to my pursuit. I have by 1995 when Digital technology overwhelm AUDIO Hifi to make the 1bit player and it's convenience...clear cold clinical sound but would not accord with the musicality, natural warm tone of the acoustic instruments that shimmers and vibrates tingling sensations and give life to music ......in the first decade of teh new century relinquish the new bright clean sounds for Proprius, Genera. Nova. But the all Important DAC has improved to reproduce through software synthetic acoustic tone ....And digital pre amp to attenuate the huge line signal. The Hifi Industry has not allowed me to fulfil my audio music development and I read and read your blogs .......to develop what is much needed for audio enthusiast ..a True GSP or DAK tone analogue Pre Amp .....incorporating an active buffer with Valveeee...ee tone between Proprious and DAC........and somewhere in the last few pages until I can digest it is the secret ...but need a Designer committed to a DAK analogue Pre amp....with an active op amp Buffer ...Can you help....
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Posted By: Graham Slee
Date Posted: 22 Feb 2021 at 10:08pm
I can certainly help. I am trying to reach that goal. The power amp had to be achieved first because of the costs involved. The costs are difficult to explain here, but have had to follow a planned direction aimed at succeeding. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Sylvain
Date Posted: 23 Feb 2021 at 4:11pm
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A capacitor has resistance and inductance. A resistor has capacitance and inductance. An inductor has resistance and capacitance. A wire has inductance. A PCB trace has inductance. Without Pre-empting any your designed concept for an Analogue Pre Amp ...I can no longer resist the temptation to ask when yours|(above) posted on 21st February at 5:20 AM reached my laptop ..... Would an Isolation Transformer deal with the of Yours above in italic and isolation transformer to achieve matching inpedence between Proprious and DAC or Genera ....Please ? |
Posted By: Graham Slee
Date Posted: 25 Feb 2021 at 9:12am
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Why would we use a non-linear device to improve the signal? The electronics world has spent the last 100 years trying to make the passage of signals as linear, and as such, least distorted as they've ever been. Harshness is caused by distortion. Harold Black was tasked to remove the distortion from telephony and invented negative feedback. Harry Nyquist developed the stability criterion to "tidy-up" the negative feedback. Those works happened 87 years ago, and since then, other engineers have developed the processes involved to improve the quality of sound. My job has been to study every avenue, and since the internet made file-sharing possible, I must have researched most of those developments. Still, we see snake-oil peddlers trying to undermine a lot of this, using baseless claims. Judging by the financial information I've been able to see, some of these companies are very wealthy. They amass the wealth through sales, from which comes profit. I can only conclude there are an awful lot of gullible customers in hi-fi. I have often said I'd like to get away from audio altogether and do something in the real world - to be able to stand at a distance and laugh at the dire state it is in. Why would you use a transformer, which will always have linearity issues, fix linearity issues? What you should be doing is dumping the products causing you the problem. I'd have thought that obvious. ------------- That none should be able to buy or sell without a smartphone and the knowledge in how to use apps |
Posted By: Sylvain
Date Posted: 25 Feb 2021 at 2:45pm
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You have a good following of people who still recognise '' natural tone of musical equiplement''....and Vinyl albeit grooved with digital Lathe and even cassette tape is beginning to return under a new design. Acoustic guitar and piano even flutes and short city trumpet horn and new design material Blow music instrument and acoustic tone is beginning to be re heard in it's natural...ness ....NOT from a laptop M-Audio DIGITIZE software ... Amplifiers are having difficulty to decide what is T, Z, D , G , H class in their digital design contruction, very clean and clear but MUSIC is not about linearity, and RIAA does not follow the rule but has pleasant warm to convey emotional content in it's natural true Tone and you cannot describe it but oNly Feels AND few are those who can design to reproduce the emotional content but the HIFI Industry seek to recondition our hearing perception and have ladies scantily dress art HIFI SHOW got lure you and glamorous scintilising colours and colours and $£,00000000 tag to represent your status b ugh NOT musical satisfaction but MARKETING is being played at it's own games these days .. .No how about an ANALOGUE PRE Amp with an Op Amp active Buffer with a VALVEE TONE...
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