Help with a pre-amp
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=567
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Topic: Help with a pre-amp
Posted By: davidc
Subject: Help with a pre-amp
Date Posted: 28 Jul 2009 at 2:31am
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I'm about to buy some Genelec active speakers which will be fed from the line out of my Novo headphone amp (what a gem). My problem is that I'd like a volume control between the Novo and the Genelecs and I think I need a preamp with a volume control for this. I've scanned the web and there seems to be nothing under £500. Can anyone here please suggest a pre-amp, or a something, with a volume control that won't hurt the signal or do so much financial damage? If it could have some XLR outs all the better....
Oh - this lack of a volume control is all because I'm not using an integrated amp - all music is from pc and cdp via a Cambridge Audio DACMagic which feeds the Novo.
Thanks
David
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Replies:
Posted By: Graham Slee
Date Posted: 28 Jul 2009 at 3:28am
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Hi David and welcome to our little community. A while ago I thought it could be a good idea to make a small-box-preamp similar in size to the Novo or Solo with limited functions and inputs to keep its price reasonable. Not many takers for such an idea until now? I wouldn't expect you to hold on for the many months it would take to get it off the floor, so unusually for me I'd suggest you take a look at Mick Creeks little preamp. I forgot what it's called but it's got three inputs and a volume control. As far as I can tell, it doesn't have any gain being a "passive" unit and that may be a drawback perhaps. I think it does have a remote control if that's any use. Ours, if it ever gets done, would not have a remote, but would have gain and my thought was to give it a balanced output. It is fatal throwing such a suggestion open to colleagues like I did: they come up with lots of suggestions of their own - so many indeed that it would have to grow to a 2U rack case to accomodate the lot, with a big price tag to boot. I'd be interested in your feedback though and anybody elses because I still feel a simple small preamp with gain (an active preamp) at a price that's sub-£500 would be attractive. ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: davidc
Date Posted: 28 Jul 2009 at 5:39am
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Graham - thanks. Thanks too for responding so swiftly. Yes, I think the Creek preamp may be this one - Creek OBH 22 Passive pre-amp? It's around £300. It has a remote which I don't need. I was staggered by the cost of most of the preamps at Stoneaudio - I don't know if they offer good value for money or not but they certainly were very expensive. I was really surprised trawling the web that there is no simple, small dedicated desktop box that you can use for controlling the volume of your active speakers. There just doesn't seem to be such a creature.
What I want is basically a Volume control on my desk to use with my Genelec 8030As. You get this if you buy the cheapest 2.1 or more computer audio speakers from Logitech or anyone else - the manufacturers don't expect you to control volume from the computer - they give you a standalone control which sometimes has a headphone socket and Line-in in it and sometimes doesn't. I just want one of those - without the headphone socket - for grown ups.
It would be great if it could have ins and outs representing the main ways that people get a sgnal to active speakers. Maybe analogue and digital ins, and analogue RCA phonos , 6.3mm jacks and XLRs outs (the latter balanced as you are thinking). But come to think about it I'm not sure if you can turn up the volume on a digital signal. Don't know about that - maybe scrap the digital in - if that's included the box will need a DAC presumably.
What does "Gain" give you? More current presumably - does that equate to more volume? But if so how can you have a Volume control in a passive box?
Pricing has to be below the level that you would think "Well, I might as well just go and buy a modest integrated amp and use it's preamp out".
I would rather buy a Novo-like box from you for about £200-250 - and I'm happy to wait - I'll have to use my son's redundant integrated amp in the meanwhile.
Oh yes, my son mentioned to me - quite independently - that he liked his Alesis powered monitors except that he had to turn the volume up and down using controls on the speakers. My case rests.
Please make the box.
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Posted By: Graham Slee
Date Posted: 28 Jul 2009 at 6:25am
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By gain I mean amplification. It doesn't even have to mean any more than a factor of 1 or 2, but it does need to buffer (give current gain to) the volume control to provide a low impedance drive to the speaker amps. In other words this is an active preamp. A passive preamp is a corruption of words - you rightly say it cannot give volume control - it can only attenuate. It does not need to be elaborate to deliver an excellent audio performance. With 3 dual op-amps (getting technical here) it could be possible to do the two balanced outs and a "utility" headphone out (not as good as a Novo but still very acceptable). Rear panel room is cramped but it may take two phono inputs (a total of four phono sockets like the one on the back of a Novo) plus the two XLR balanced outs. A third input could be a 3.5 front panel jack neighbouring on a 3.5 jack for headphones out. If that won't fit, each balanced out can be done on a "stereo" or Tip-Ring-Sleeve jack like a number of pro-mixers do. Using the Novo case it could well be possible to do it for £250. Anyone else interested? ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: iamalexis
Date Posted: 28 Jul 2009 at 9:42pm
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have you had a look at the "big knob" made by mackie. i don't think this quite fits the bill as it is more for studio control rooms but i thought it was worth a mention.
http://www.mackie.com/products/bigknob/index.html i also found this: http://www.smproaudio.com/produkte/monitor-controller.html i have no experience of either, although i know a few people who use the "big knob" in their studio and are happy with its performance. |
Posted By: davidc
Date Posted: 29 Jul 2009 at 12:41am
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Thanks very much for this steer. There are one or two runners there. This is a particularly relevant thread which your link indirectly led me to:
http://www.soundonsound.com/forum/showflat.php?Board=PCMus&Number=748438 - http://www.soundonsound.com/forum/showflat.php?Board=PCMus&Number=748438
At least I now know there are some possible boxes out there
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Posted By: davidc
Date Posted: 29 Jul 2009 at 12:58am
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...this looks to be what I need -
http://www.makingwavesaudio.com/browse/recording-equipment/passive-volume-controls/sm-pro-audio/sm-pro-audio-m-patch-2.html - http://www.makingwavesaudio.com/browse/recording-equipment/passive-volume-controls/sm-pro-audio/sm-pro-audio-m-patch-2.html
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Posted By: Andy9672
Date Posted: 06 Aug 2009 at 10:16pm
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You could aslo look at the Pro-ject range, they make a passive preamp that has had a lot of praise for the price
------------- Solo psu1 Rega Apollo AT W1000 Technics SL1200 |
Posted By: Graham Slee
Date Posted: 09 Aug 2009 at 4:23am
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This community is paid for by the proceeds of Graham Slee Projects Limited and as such has a policy of not allowing the promotion of other brands that could be classed as competitors. If a member wishes to let another member know such things the private messenger service provided for free by us to members should be used. No other manufacturer's forum I am aware of would allow promotion of a competing brand. Admin. ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: Andy9672
Date Posted: 09 Aug 2009 at 5:55pm
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Sorry Graham i didnt realise you made a pre-amp (other than your great phono amps).
------------- Solo psu1 Rega Apollo AT W1000 Technics SL1200 |
Posted By: Andy9672
Date Posted: 09 Aug 2009 at 6:04pm
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Sorry again Graham, just re-read your post, though i wouldn't class them as competition though.
------------- Solo psu1 Rega Apollo AT W1000 Technics SL1200 |
Posted By: Graham Slee
Date Posted: 09 Aug 2009 at 9:38pm
All is forgiven in that case  ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Andy9672 wrote:Posted By: Graham Slee
Date Posted: 09 Aug 2009 at 9:48pm
Just designing one hopefully to launch in the Autumn partly in response to this topic. I've been often asked for a box that does "single-sided" domestic in to balanced out. Or in this case a volume control with same. And often requested to simply do a two or three input preamp. It would seem there is room in the market for an absolutely-no-frills "little box" preamp, and there are passive ones, but often some gain (amplification) is required for matching a low output to a high input power amp - plus, balanced cannot be done passively. And seeing that used to be my daily "bread and butter" job some 16-20 years ago... One or two loose ends to tie up and I'm on to it. ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: Andy9672
Date Posted: 09 Aug 2009 at 10:07pm
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i always wondered if you could increase the gain using a transformer bassed passive preamp. I did think of going down the passive route but got a pre amp with the power amp i found. Looked at a ladder design volume control and thought you could do a balanced version with this? ------------- Solo psu1 Rega Apollo AT W1000 Technics SL1200 |
Posted By: Graham Slee
Date Posted: 10 Aug 2009 at 3:49am
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Andy, It's been done with transformers. The only difficulty is that transformers do it by impedance ratio, which means you can only have voltage "gain" with current "loss". Take the phono cartridge step-up transformer as example: its input is low impedance (high current) and low voltage to match a moving coil, and its output is high impedance (low current) and higher voltage to match a moving magnet. Somebody told me about a transformer "preamp" which had input impedances of 100k and a gain of two... A 200k output impedance isn't much good at driving a 22k input impedance power amp... It gives you a net loss - never heard of that "preamp" since. As transformers are taught at technical college at HNC level you'd have thought the penny would have dropped with this particular designer? Obviously it didn't as he was no engineer, period. A balanced output has one input and two outputs, one inverted in phase by 180 degrees to the other - it can only be done using a real amplification device such as a valve or transistor. It can only have gain if done with more that one valve or transistor (and associated support circuitry which has to include a power supply). Actually, thinking about the above, it can be done passively with capacitors and resistors but only at one narrow band of frequencies, and would have such an insertion loss as to be completely useless. Just in case some think it, the above is in no way Graham Slee guile - it is a bit of scientific fact. ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: Andy9672
Date Posted: 11 Aug 2009 at 9:03am
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Amazing the number of companies that put products onto the market without knowing how they work!
------------- Solo psu1 Rega Apollo AT W1000 Technics SL1200 |
Posted By: iamalexis
Date Posted: 15 Aug 2009 at 1:22am
Graham I'm intrigued to know more about this, are there any more details you can share with us 
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Posted By: Graham Slee
Date Posted: 16 Aug 2009 at 12:56am
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OK. In a simple analogue signal system (one that doesn't need digital to analogue conversion because other equipment does it) where there are few sources, such as CD, Phono Amp, Computer/iPod to name three, such users would only really need three inputs. As for a recording output, why? I remember recording cassettes in the dark ages for the car. If you want to copy a CD you'd simply pop it into the DVD RW tray on the computer and burn a copy. If it's on computer you just duplicate it on the computer. If it's vinyl then maybe, but a split feed - one to control preamp and one to computer will suffice. So do we really need rec-out? What most power amps want is drive voltage. A passive pre can't add voltage, it can only lose it. Then there are active loudspeakers - loudspeakers with amps built in - not the cheap computer things with 10 zillion watts pmpo that wouldn't tickle a gnats ch.... , but grown-up types. There always seems the need for balanced outs even if it's just to boast to the mates... And then there are proper uses for balanced outs such as driving a long cable. Or for professional users who use balanced lines to avoid ground loops. But a full blown pre which does music well costs £?,???.??, which is OK if you can afford to blow that amount for a simple analogue system, but a £250 little box solution can sound as good if not... If possible I would fit it in a case the size of the Novo because we can get them at a good price in bulk, and they look good. It would not take up valuable hi-fi real-estate. However, it does mean hefty interconnect cables could cause it to do a wheelie, but at that price blu-tack wouldn't be objectionable??? So round the back the usual 4 way phono block we use for two inputs, and a 3.5 jack on the front for the computer feed - howzat? If OK, then 2 x XLRs on the back if they'd fit. The other way of doing balanced is two TRS jacks - one per channel (a normal 1/4 inch stereo jack socket) wired phase=tip, antiphase=ring, ground=sleeve. That's what "busy" mixers use for balanced ins/outs, such as the rack-width Soundcraft's. On ocassion the serious pro-user will want B-guage (PO) plug compatibility and that can be accomodated. So what else? No remote control - we need the exercise - and some would get used on the desktop anyway. Input switching using a simple manual rotary "dry-contact" (Gold plated contacts) 3-way switch. Volume. Balance. No room for tone controls on this one, but use one of our phono preamps - they sound good... Perhaps a very simple headphone output??? And there you have it. OK, forgot the power supply. PSU1 or wall-wart. The "power share" thing I'm putting into action allows anything we sell with the power share feature (to be announced elsewhere) to share its power supply with another power share item. ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: mrarroyo
Date Posted: 16 Aug 2009 at 2:48pm
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A headphone out would be good if it sounds as good as the Novo's. Otherwise it may take up valuable real state in such an small enclosure. ------------- Miguel |
Posted By: Andy9672
Date Posted: 18 Aug 2009 at 6:59pm
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Making the pre using phono blocks with the option of having a xlr/po plug at extra cost? to have all wire comectors on the back, i like to have a neat front to my equipment!! Also you could make a simple tone control using your 3 way switch, one for trebel one for bass with a 3db add or cut? i would leave the headphone out but build in provision for two pre outs, one for the power amp one for the headphone amp and all of a sudden your fitting a huge amount of connectors onto the back of a very small box!! ------------- Solo psu1 Rega Apollo AT W1000 Technics SL1200 |
Posted By: Graham Slee
Date Posted: 19 Aug 2009 at 12:07am
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Having listened to what you say and having surveyed the rear panel of the Novo sized case, I can provide plenty of ins and outs round the back provided that a compromise can be tolerated? I can provide phono sockets (RCA jacks) on two inputs (that's four sockets/two pairs like the back of the Novo/Solo/etc) Balanced outputs not on XLR's but the alternative: TRS jacks like on mixers (1/4 inch stereo jacks wired differently) And now the compromises... A third input on a 180 degree DIN socket (like Naim use/used) An aux in/aux out (pre-out) on a 240 degree DIN socket. So, that's really 4 stereo ins and 2 stereo outs (one being balanced on left and right TRS jacks). And no wires into the front. Acceptable? At the price? As for tone, I could try a similar "slope" switch: up-position favouring the highs; down-position favouring the lows; and mid-position flat. Input switching to use a similar 3 position switch controlling relays to minimise cross-talk -- that would fit. Yet another 3 position switch selecting aux-out / nothing / aux-in (the nothing position being similar to the non-shorting Solo "mute") And a volume control. Are we there yet? Or will we need a balance control? PS. I thought of calling it the Aria ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: iamalexis
Date Posted: 19 Aug 2009 at 1:29am
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i'm liking the sound of this...i would have a 35mm headphone type socket instead of the din input. i would use this for connecting an mp3 player, built in soundcard on laptop, iphone docking station, tv headphone out etc. i think if you were to include a headphone output (i think you should if you can, especially if it is close in quality to the novo) this could be situated next to it on the front panel to allow easy access for plugging in different sources.
i think din type connectors maybe a little scary for those not too familiar with the world of hi-fi. does the 240 din connector have an input and output on one connector? having a second pre amp out would be a nice feature to allow plugging into a headphone amp, soundcard i/p etc. the trs jack outputs make sense for plugging into a power amp or powered monitors. i like the idea of the tone control but don't think a balance control is necessary. for the switching could you not just have one switch for the inputs only. the aux out could always be "on." "hefty interconnect cables could cause it to do a wheelie..." it would be good to come up with a solution to this. i imagine this being a nice compact desktop unit which would sit solidly in place. like the name too
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Posted By: Graham Slee
Date Posted: 19 Aug 2009 at 2:45am
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I guess the pre-out which is not the main preamp output (those are on the 1/4" TRS jacks) could be "subordinated" to a 3.5 jack on the rear? (by the way, the TRS jacks can also be used "unbalanced" for single sided power amp inputs) Also aux send and return (used to be tape loop but I guess nobody uses tape anymore?) seeing they're most likely going to be used with some form of computer/iPod could also be 3.5 jacks? All the above being on the rear... Duplicates on the front could be OK, but reliable break jacks in 3.5 size are a bit of a laughing matter and therefore I'd have to rely on the user not plugging both to front and rear at the same time? Maybe I ought to just stiock with 3.5 jacks on the rear for aux send and return, and one for pre-out. And round the front input 3 on a 3.5 jack and headphone out also on a 3.5 jack? I think that may appease most everybody? The question being can I fit 2 3.5 jacks, a mini volume control for headphones, input selector "toggle", tone gradient "toggle" aux send/return "toggle" and main volume control all on the front? I shall draw it on the computer and see. (toggle refers to the 3 position up-down switches as seen on some of our other products -- the "nothing" position would only cut the feed to the main and pre-outs but the aux out would not be interupted) ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: mrarroyo
Date Posted: 19 Aug 2009 at 2:51am
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How about instead of a rotary volume pot a digital one? It may add to much cost though. ------------- Miguel |
Posted By: Graham Slee
Date Posted: 19 Aug 2009 at 2:52am
Maybe on the headphone out? ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: iamalexis
Date Posted: 19 Aug 2009 at 9:00pm
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i was having a think about the din versus 35mm headphone sockets. if you were to use the din connectors i suggest providing "graham slee" looms/breakout leads. this is what made me think of it (a compact soundcard with lots of i/o options)...
http://www.apogeedigital.com/products/duet.php i also wonder if you were to use 35mm headphone sockets, it might be worth supplying leads to work with these? i think a 1/4" headphone socket for the headphone would be a better bet. a smaller volume pot for the headphone makes sense to me. i don't think i know what a digital volume control is? |
Posted By: Graham Slee
Date Posted: 19 Aug 2009 at 10:51pm
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Thank you for that answer -- it helps a lot. I think we need a poll on DIN versus 3.5mm jacks. Quite happy to do a cable/loom selection but some people have their favourite interconnect cable brands which most of the time are unfortunately not us. A digital volume control is similar to the up-down buttons on a remote control. Except for the motorised volume controls you get on expensive gear, usually it's a voltage controlled amplifier stage similar to that used in cheap cassette recorders that did ALC -- automatic level control. They can be done pretty well these days and voltage controlled amplifiers (in effect a little sub-circuit) have been used for years in studios -- the expensive Penny and Giles sliders simply controlling a DC voltage. However, I'm looking at a miniature Alps volume control instead to 1] keep the price reasonable and 2] make it all fit the drinks coaster sized/palm sized case footprint. The smaller the parts, the more I can offer. ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: Andy9672
Date Posted: 20 Aug 2009 at 9:13am
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I would rather have a DIN socket than a 3.5mm jack, i have had so many problems with small jack sockets. Thanks to some other manufactures there are plenty of 5pin DIN to phono/jack cable available on the market, my local Hi-Fi shop sells cables from five different companies. I agree with the small Alps pot as the volume control, allways thought they sounded strange but as i now have one on my pre-amp and one on my Solo I have to change my mind!! Shame you can't lead line the bottom of the case, help with sheilding and stop it doing a wheelie! Just an idea but could you use your cases sidewards and have the extrusion cut to a longer length, be a bugger to get the pcb, guts in the box but it would give you more front and rear surface area to play with. ------------- Solo psu1 Rega Apollo AT W1000 Technics SL1200 |
Posted By: Graham Slee
Date Posted: 20 Aug 2009 at 1:49pm
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The EU banned Lead in electronics equipment because at the end of its life when buried in landfill it can disolve in water causing a health hazard... So what about all the [rain] water coming off church roofs? ................................... We could fit a steel plate but it would increase shipping costs as the extra weight consumes more fuel. However, because this is a small unit [palm sized] it could fit near the front of the hi-fi rack or on the front of a desk, then the cables coming out of the back would rest on the hi-fi rack shelf or the desk, and then it would not tilt. Therefore we have saved the world! My question regarding 3.5mm jacks is really asking "just who uses them?" The problem with the 3.5mm jack goes back to the 70's when there were two types -- the difference between them was sufficient to make a very bad connection -- I wonder if anybody else realises this? By the looks of things the two types are still in existance. Otherwise they would work extremely well when you consider the actual contact area of other connectors. ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: Andy9672
Date Posted: 20 Aug 2009 at 1:59pm
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I only use 3.5mm jacks for my headphone in my Ipod, thats it. I didnt reaslise there where two different types of 3.5mm jack available, that would explain a bit. Like using a 1/4" jack in a bantam socket. never good ------------- Solo psu1 Rega Apollo AT W1000 Technics SL1200 |
Posted By: discrete badger
Date Posted: 20 Aug 2009 at 7:22pm
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I have to say I think the decision to use a Novo-sized case is the right one. Large enough (hopefully) to squeeze in the innards and the connectors, but small enough for people to find space easily on their audio equipment racks or on their desktops, and even not think twice about transferring it in between. Besides, it seems to be a bit of a tradition at GSP to produce big sounds out of small and unassuming boxes! How would the quality of a "basic" headphone out relate to (say) that of the Voyager? It could be another selling point for a number of people who would find it a huge improvement over the sockets on their other equipment. |
Posted By: iamalexis
Date Posted: 26 Aug 2009 at 12:41pm
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i think the 3.5mm sockets would be a good use of space. is there any durability/reliability/sound quality issues associated with this type of socket.
i might be sticking my neck out a little here but i think the 3.5mm tyoe of socket is less old fashioned than the din type (with my dad's old quad 33/303 i always used to struggle to find decent connectors for it). |
Posted By: Graham Slee
Date Posted: 11 Jan 2010 at 12:33am
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Four and a half months later... How time flies. The first prototyping session is underway of the Aria line preamp. Currently the design is discrete transistor. A stage specifically designed to be differential input and differential output in-one. These are early stages, but I must admit to getting rather impatient and wanting this finished darned-fast! By now I'm sure much of the momentum of interest may have disappeared? The same four transistor stage, if successful in listening tests, would be used for balanced to single sided inputs, single sided inputs to single sided outputs, and from single sided inputs to balanced outputs. That's a total of 6 stages: 3 for left - 3 for right channels, and a total of 24 transistors... and I've somehow to squeeze it all, including switching relays, into a Novo sized box ??? Well, I've done worse (I think...) No time tonight to take photos but if it does the sonic miracles, I'll show you how it looks right now in a few days time. I do hope it works out because this circuit is one of those "no negative feedback" designs folks get so excited about! In actual fact, there is no such thing as no negative feedback, but if we get the audio projects magazine launched I will do an expose on that subject. ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: iamalexis
Date Posted: 11 Jan 2010 at 11:52pm
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that's great news...looking forward to finding out how the testing goes and seeing some pics
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Posted By: iamalexis
Date Posted: 03 Feb 2010 at 11:30am
| i wondered how the testing is going? |
Posted By: Graham Slee
Date Posted: 03 Feb 2010 at 11:29pm
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Testing a bit delayed because of the crappy bits in business such as year-end accounts... But here is a picture of the "rat's nest" working prototype of the amp configuration I believe will do the biz. This is how I normally start a product's development - I'm not a proud chap or a snob, so I don't really care how such people from some forums will react to seeing what looks to be a complete mess...  The thing is, it measures up great! This is again discrete, not that I have anything against op-amps, just that we don't need mega-gain for a line stage. Just three small signal transistors (per channel) are configured to perform each stage of the line amp: balanced input, main gain stage and balanced output - a total of 18 transistors to squeeze into a Novo sized case... Just hoping I still have the knack! Listening to it as I type, I am quite surprised: I think I could easily sell this as it is and put it up against the "big boys" - I may be sounding a tad complacent, but this is the sort of sound I like. Anybody who knows The Moody Blues "Every Good Boy Deserves Favour" album, will realise how difficult it is to get it to "wake-up" - this stage somehow does it. Anyway, here's what I measured so far... Clip level: +15dB single ended/sided/unbalanced (a bit more tweaking should get it up to my preferred +16dB), which will be +22dB on a balanced output (OK, the big stuff can do a tad more, but this is a budget miniature) THD + Noise at +10dB out 0.05%; at 0dB out 0.02% Frequency response: less than 12Hz -0.5dB (the lowest I can measure on this test set) to 72kHz -3dB, or 35kHz -1dB Gain: +8dB (unbal. out) Noise: -84dB CCIR Q-pk 22Hz - 22kHz (measured at output with vol control set to worst 3 0'clock position) And this is on a scrap piece of used strip board. 
------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: mrarroyo
Date Posted: 04 Feb 2010 at 12:16am
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Graham, I had forgotten all about this! Glad you did not. ;) ------------- Miguel |
Posted By: iamalexis
Date Posted: 04 Feb 2010 at 6:03pm
| glad to know it's going well and looking forward to the end results. |
Posted By: Cyreg
Date Posted: 16 Mar 2010 at 4:31pm
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Graham, you are a big fan of controlled wide bandwidth freq response, I did learn?
Somewhere is explained it has to do with unwanted "phase-shifts", which smear up the sound or something alike.
 Is this no problem with the limited bandwith of this prototype? Has to do with transistors?
Or did I understand former explanations with the wrong interpretation?
 Just curieus  ------------- TecnoDec/RB250/MP110>GramAmp2C/PSU1; Cyrus CD8SE; > Exposure 3010S2D INT > Harbeth C7ES-3 '35th Anniversary' cabling: IC 2x DNM V3; LScable Exposure DMF-two; Furu TP60 + MWaY and BlackCable pc's |
Posted By: Graham Slee
Date Posted: 16 Mar 2010 at 11:50pm
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In this world of incredible modern technology that never goes wrong... (pause for howls of laughter from the wise) it may be hard to believe that electronics is far from perfect - propped up by fixes and sticking plaster.... Whether it be a valve or transistor, here is a sobering thought: it all came from the dust beneath our feet! And if anybody doesn't believe that last statement I am very sorry for their sanity. Yes, the human race has done wonders and miracles with bits of clay and iron, and it would seem it's near as damn it to perfection... No way! The human race's understanding of electronics is like a 3 year olds understanding of quantum physics! Pathetic. Not that I'm any better (well maybe a smidgin )You really don't want to know the truth? Until a few years ago nobody realised some of the "best" hi-fi designs were completely unstable. Since then we got high powered simulators (paid for ones - not the freebie downloads) and discovered things those old boys didn't know about their "great" designs. Yes, they went all out and would do a Meg but what next? The response would then plummet like a brick falling off a skyscraper. If at the same time there was gain plus a stimulus, you have an oscillator. But that's OK because music doesn't go that high... But radio frequencies do! And there's the stimulus. Take a look under the bonnet of all those rave products of yesteryear (and you don't have to go back too far) and look at all those RFI prevention components... If an amp rolls off gracefully before the components decide to do it for it, then you should never need RF control - the amp cannot go into the regenerative mode required to tune in a station efficiently (ever heard of the "regenerative receiver"?) But because electronics isn't perfect like some models suggest, it is worth filtering an input anyway. So, what goes up must come down. When we had valves we didn't have the gain we demand from op-amps, so we had a wider bandwidth before the output drooped, but even with valves, the droop wasn't nice and controlled like we'd like to think. However, this chap agrees the valve sound was nice... whilst the valve was working... Once the output drops, and if we bring it down at the right slope, which means 6dB per octave whilst ever the gain is more than 1 (unity), it will be stable and sound better than an output that oscillates or at least rings badly. Op-amps can do that! But with all that gain, they start drooping at just a few tens of hertz (unless it's one I picked for something like the Era Gold V). So that droop is in the audio band and its phase displacement at 6dB/octave is 90 degrees. But the input is zero degrees. Anyway, to set the gain, negative feedback is used, which also cures distortion... ? It may cure THD, but the negative feedback is trying to turn 90 degrees back to flat. Take each hertz at a time and analyze what's going on, then step to the next hertz and so on - phase distortion/modulation. With valves the open loop (before negative feedback) bandwidth wasn't brilliant, but wider than todays op-amps. Then you get op-amp designers going public to say how good their designs are and the op-amp droops that early you can't even see a flat on the graph.... You even get valve nuts trying it and agreeing it's good, such is the frenzied hype. What I'm saying is what I say here...  from http://www.phonostagepreamp.com/reflexmcphonostagepreamp.htm - http://www.phonostagepreamp.com/reflexmcphonostagepreamp.htm Even a slight improvement in open-loop bandwidth results in a better sound - just ask our customers (yourself?). And this is what was being bandied about by the early eighties hi-fi press, and they were right. Now, what was the question? By now I've forgot - must be 'cos I'm over 40  ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: Lucabeer
Date Posted: 17 Mar 2010 at 9:04am
I agree! This is pure math and quite easy to understand... and it's incredible to think that other makers don't give the right amount of attention to it. Higher open loop bandwidth and gain = higher crossover frequency = higher phase margin when feedback is applied = less residual distortion at high frequencies of the hearing range Sure, one can design a compensating network so that even if the open loop gain/bandwidth is not large, the closed loop amplitude response will be reasonably flat and extended in bandwidth. But whenever one takes a look at the phase plot too... the shock! The horror! |
Posted By: BAK
Date Posted: 03 Apr 2011 at 4:53pm
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"How time flies. The first prototyping session is underway of the Aria line preamp. Currently the design is discrete transistor. A stage specifically designed to be differential input and differential output in-one. These are early stages, but I must admit to getting rather impatient and wanting this finished darned-fast! By now I'm sure much of the momentum of interest may have disappeared?" Graham any new developments on the PreAmp? Will it still be in the offering?
This project is very attractive. I don't think the interest has gone away, only distracted.
 Having a complete solution from input source to speaker driving output would be great.
 And DIY building it in stages would be very satisfying. I like the idea of individual level controls for different input types to match levels. A separate gain setting would also be good to set the normal listening level at 12 o'clock on the volume control; and still be able to crank it up for abnormal listening situations... PARTY!
The master gain setting could be set for maximum output to not overdrive the power amplifier.
Maybe have 2 versions: one for average audio enthusiasts and another for those who need or request balanced line drivers and connectors.
Bruce
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Posted By: Graham Slee
Date Posted: 04 Apr 2011 at 8:34pm
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I remember pre-amplification was a lot more flexible with an audio mixer - any views? ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 06 Apr 2011 at 8:54pm
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No takers to last comment then? Actually, I would definitely find the flexibility of some audio mixer properties of value. I suppose it's OK to have level matching adjustment on each input of a preamp, but a mixer does that for you already. It could be argued that the user would have to turn down an unused input whilst using another to get rid of any residual noise from an unused input, but there is the possibility of using PFL or "booth" buttons which send unused inputs to another mixer bus which achieves the same end. Maybe I'm getting too technical again or most people don't understand audio mixers? All you need do is ask - you know that most of the time I'm happy to explain/expand on a subject. Graham ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: BAK
Date Posted: 07 Apr 2011 at 3:02am
An input shorting switch used for those inputs not in use would be good. I have seen FETs used for this purpose. I can imagine a set of FETs used for input selection and another set of FETs used for muting unused inputs, all controlled by the same control voltage. One brand used CD4016 quad switches for input selectors having only 100 ohms in series with the signal path when "on" (I am not sure of the musicallity of such CMOS use). Another uses special contact relays to select inputs. Relays add the muting very easily using NC contacts when at rest.
The individual input level controls could be set screw type next to the respective input. I would think 3 inputs would be enough for a small preamp with input selector.
The master gain I mentioned before would be an added plus for 2 reasons: first
to keep others from turning up the system too loud or into overload,
and second to set the gain so normal listening is at 12 o'clock on the volume control.
To keep it safe, the master gain setting would be best located on the rear or some how hidden. It could be switched, one position for "normal" and another for "maximum without distortion"; each position with it's own set screw level.
All of these set screw levels could be hidden behind a removable panel so as not to overpopulate the rear or front panels. Front would have: POWER sw, Volume, ON LED, INPUT selector, and NORMAL/MAX gain switch.
These are my ideas from years past and I have never put them into solder.
Bruce
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Posted By: BAK
Date Posted: 07 Apr 2011 at 3:16am
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Graham, what are your thoughts on voltage controled amplifiers?
Can a low noise op-amp be voltage controled via a FET in the feedback loop and not detract from the sound quality?
If so, one could make a remotely controled amplifier stage very close to the input selector and have the control anywhere on a chasis.
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Posted By: BAK
Date Posted: 07 Apr 2011 at 3:27am
The selector and input level controls could be on a separate PCB very close to the input connectors
OR
housed in a separate box to facillitate a FET or RELAY switch circuit with it's own power supply regulator for the FET bias or RELAY control.
The separate housing would keep noise to a minimum.
Just some ideas...
Anybody else interested?
Bruce
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Posted By: frimmers3
Date Posted: 26 May 2016 at 1:59pm
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I wonder if anyone could help....I use an AR Legend turntable with a Goldring G1042 cartridge, a Graham Slee Amp2se through an Arcam Delta 290 integrated amp,feeding a pair of Wharfedale Diamond 220's stand mounts,with Chord interconnects/speakers throughout...Not "high end",but very pleasing to these old ears:)....cut to the chase....I have sourced a mint Arcam Delta 290P (power amp),and intend to bi-amp my system,with the integrated amp providing the high frequencies,the power amp the low frequencies..What (if any) advantages could(should) this measure provide? Thanks for any constructive criticism! ------------- Rega P8,Audionote IQ3 mm cartridge, Accession mm. phono stagewith Enigma psu Graham Slee /Chord interconnects, Spendor A2 floor stand speakers |
Posted By: Chris Firth
Date Posted: 26 May 2016 at 2:41pm
I've never heard a passively biamped system, so I don't what difference there will be, if any. You do end up with a power amp driving each speaker driver, but the filtering is passive (ie subractive of the signal). At best you might hear an improvement, at worst you'll hear no improvement |
Posted By: frimmers3
Date Posted: 26 May 2016 at 2:43pm
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Thank you! ------------- Rega P8,Audionote IQ3 mm cartridge, Accession mm. phono stagewith Enigma psu Graham Slee /Chord interconnects, Spendor A2 floor stand speakers |
Posted By: frimmers3
Date Posted: 26 May 2016 at 2:56pm
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Given that Arcam are (I think) a reputable company,this is what they say re the steps I intend to take.."If you are using a Delta 290,a Delta 290P can be added to bi-amplify a pair of bi-wireable loudspeakers. THIS WILL REAP SUBSTANTIAL IMPROVEMENTS IN SOUND QUALITY i F THE FOLLOWING PRECAUTIONS ARE OBSERVED" etc etc...Would Arcam make a claim like that if no improvement was afforded? ------------- Rega P8,Audionote IQ3 mm cartridge, Accession mm. phono stagewith Enigma psu Graham Slee /Chord interconnects, Spendor A2 floor stand speakers |
Posted By: Chris Firth
Date Posted: 26 May 2016 at 3:42pm
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I'm surprised they didn't use the phrase "the differences are like night and day". It could be hyperbole, or it might indeed be an accurate description of the improvement they heard with whichever brand of speakers they were using. What did they cable their system up with, because that will have a bearing on things too. A lot depends on the cabling you use - I've heard inappropriate cabling make a decent system sound broken. A lot depends on your speakers and where the crossover points are. If your tweeters are handling a lot of the upper midband then the difference could be staggering, if not then the difference will be less so.
It's unlikely, but the substantial bit could be overstating things a bit. I'm not saying that it is, but it might. They'd also sell a good few power amplifiers by making such claims. The only way you're going to know whether or not it works for you is to try it. |
Posted By: frimmers3
Date Posted: 26 May 2016 at 3:48pm
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Proof of the pudding as they say:) ------------- Rega P8,Audionote IQ3 mm cartridge, Accession mm. phono stagewith Enigma psu Graham Slee /Chord interconnects, Spendor A2 floor stand speakers |
Posted By: DaveG
Date Posted: 27 May 2016 at 4:13pm
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I used to have an Arcam A85+P85 set up. I thought it was a bit better than just the integrated on it's own, but not massively so. Same applied to when I had a pair of Moth stereo 30's bi amping. I haven't been inclined to go the same route since - in fact I don't even bi-wire my speakers any more and I've been happy enough using an integrated for years. I suspect the performance gains of using true monoblocks (like the Proprius) are greater, but it's a little hard to quantify what amount is down to it being a monoblock, or what is down to it simply being a better amp full stop.
------------- Dave Michell Gorbe + HR PSU -> Cadenza Bronze -> SME V -> Elevator -> Accession -> Proprius -> B&W CM6 s2 | Cusat 50 & Spatia cables ->
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Posted By: Fatmangolf
Date Posted: 28 May 2016 at 11:16am
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I do biwire my speakers with Spatia cables (of course!) but in an older system some years ago I found biamping made little difference unless I was listening very loudly. If I had the money to spare I would love to bi-amp with another pair of Proprius amps, perhaps I should try this with the loan pair? The sound I get now with my two is much better than any previous amps I have tried and can go louder than I wish to listen! ------------- Jon Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC. |