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Interconnect BS vs Science

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CageyH View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CageyH Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2022 at 9:22pm
The cable I chose to make my balanced interconnects from uses PTFE as a dielectric.
Not too shabby if I am not mistaken. It also has aluminium foil and copper braid shields.
The conductors are made of UP-OCC copper in a twisted pair, which I have soldered to some silver plated Neutrik XLRs. I make them up myself mainly due to being a cheapskate, and because I can make the exact lengths I need to avoid having excess cabling behind my rack. 

I was tempted to try a more exotic connector than the Neutrik XX series plugs until I saw the prices.
Kevin
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Post Options Post Options   Thanks (2) Thanks(2)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2022 at 10:20pm
Nothing wrong with Neutrik's
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2022 at 10:29pm
I use them too.
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ash Quote  Post ReplyReply Direct Link To This Post Posted: 06 Mar 2022 at 12:11am
I always think about refractive index, n, when I see you write about VOP %.

n=v/c (speed of light in the medium / speed of light in a vacuum)

I doubt this is a coincidence.

Also:
c= 1/sqrt[(epsilon)0·(mu)0]
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 06 Mar 2022 at 5:27am
Ferrites add inductance to wires, making them higher impedance on reaching, and exceeding their frequency range. Tiny ferrite beads would be threaded onto transistor base leads to get rid of radio breakthrough. I'd learned this as part of my RSGB exam course (the exam I didn't take). But I thought every electronics guy would know that, so perhaps the "university lecturer" didn't do the radio ham stuff?

(I could not afford to fight the UK government - its advertising standards department. Not that the government itself is squeaky-clean - party's etc. They were effectively denying the workings of physics.)

By clipping the RS Components ferrites onto the DVD cable (Nottingham University job, 2003), and adjusting their position to a point where the ghosting stopped - so we all got paid - I'd obviously discovered something and that something remained at the back of my mind until after the development of the Bitzie DAC, some 10 years later.

I was sure the Bitzie DAC could do better sound quality than I was getting and started to investigate boutique USB "audio" cables. Even with OFC copper and gold plated terminals, I couldn't detect any difference compared with a stock short USB printer cable.

At that time, we were also looking into placing ferrites on an audio coaxial cable (which became the Lautus). Simply placing a ferrite tube anywhere on the cable gave no audible result, until I started to increment its position inch by inch. It seemed that at one position the bass improved. I wanted to know how.

Since 1995 it has been incumbent on audio equipment manufacturers to comply with EMC regulations, which is easier to understand if you'd done such as the RSGB exam (which I didn't sit). And because EMC testing using trial and error costs the earth, it is better to understand what's involved. When you do, then you can self-certify and avoid costly EMC certification - but you have to be able to provide convincing evidence should you be hauled in front of a committee. I trust the reader will understand the responsibilities we take and put it in perspective with the BS they seem often conned with.

So, back to the studies. I mentioned earlier about signal propagation. Go over to https://en.wikipedia.org/wiki/Signal_propagation_delay
and have a read, as it will save me having to explain it here.

Note this quote from the text: "Wires have an approximate propagation delay of 1 ns for every 6 inches (15 cm) of length"

You might think that we're talking about ultra high frequencies and skin effect etc, but note the salient point from my earlier post: "Delay is independent of frequency". That comes from the aviation industry - not Hi-Fi.

I am sure computer network geeks will also know about this, especially those dealing at an infrastructure level, such as Ethernet over 500 metres of cable?

It suggests that a wavelength has a length in a cable. It must have, and in radio ham'ing, antenna cable lengths are tuned using a VSWR meter. That's something I remembered from my RSGB studies.

In other words, a number of cycles of a frequency fit into a length of cable a number of times. There are actually calculators online which will tell you the length per frequency. This is not the fairy tale stuff of pretend interconnects, it is real science - the sort the world depends on.

Therefore, as the signal "travels" along the cable, it starts at zero - which is a node, and either goes negative or positive, depending on phase, and reaches its first quadrant - which is an antinode, and then its next quadrant which is zero - and a node again, before reaching it's third quadrant - which is its second antinode, and then completes its first cycle at the fourth quadrant - which is again a node.

For a particular frequency there is a particular length: "Wires have an approximate propagation delay of 1 ns for every 6 inches (15 cm) of length"

I'll let you digest this before embarking on the next stage.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ash Quote  Post ReplyReply Direct Link To This Post Posted: 06 Mar 2022 at 6:53am
If your research is based on existing knowledge in specialist fields and you can direct ASA to the relevant literature and references, how can they deem your marketing to be false. I would Harvard reference every single bit of supporting evidence I could find and link it to real world scenarios where it is obviously verifiable.

It is a shame that you don't have a lab where you could irradiate a length of cable with high intensity radio waves in the MHz range you wish to attenuate and have a machine that precisely moves a ferrite ring through the cable sheath then measures the dip in response at and around the chosen frequency (corresponding cable position).


Edited by Ash - 06 Mar 2022 at 7:13am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 06 Mar 2022 at 9:34am
Based on the notion that "Wires have an approximate propagation delay of 1 ns for every 6 inches (15 cm) of length", at a frequency of 100MHz the first antinode should appear at 15 inches.

Originally posted by Ash Ash wrote:

VOP % = Velocity of Propagation, given as a percentage of the speed of light?

From what we know, insulation conducts badly (that's what all secondary school science teachers teach at some point in the syllabus). The wires are insulated and so the insulation must have a braking effect on the signal. Cable manufacturers quote the VOP percentage (OK, they don't quote it on mains flex, but you can work it out). By quoting it, it must exist?

(the ASA "snitch" was in denial about this and the ASA chose to believe the "snitch")

I wanted to know where, in a particular cable, the first antinode of a particular interfering signal occurred.

A property of a ferrite tube is that it can work as a transformer, and that property is used in power line filters to reduce interference. By transforming two wires against each other there becomes an effective short circuit at a particular frequency.

In the current probe I've been working on - and with, it can have a single turn and still produce the required current measurement. It is better from a resolution standpoint to have more turns, so the current probe has ten turns to return a volt per amp reading. I include this to aid the reader's imagination in understanding the following.

The smallest number of turns you can have is a half turn. This is where a wire passes through the permeability of a ferrite.

The ferrite increases the impedance of the wire passing through it for frequencies in which the ferrite is designed to attenuate. By mutual inductance, two wires passing through it loose energy to each other as in a shorting transformer, or differential choke used in a power line filter.

Therefore this must have an attenuating effect on signals "passing through" a cable, but all so often has no effect.

However, placing the ferrite in a determined place along the cable had the effect of clearing the ghosting image on the DVD cable.

What must the coincidence mean. What way can we work out where to put the ferrite?

First we need to know the interference frequency. Is that anybody's guess or can we find a spectrum of interference frequencies that include some common ones that apply to most if not all locations?

In my essential EMC compliance work, I have to know these things, and I have books written on the subject by Keith Armstrong, who is an authority on EMC. Otherwise he's known as Cherry Clough Consultants. Therefore the ASA used Keith Armstrong's evidence in their court case against a knitted cable distributor, but would not accept evidence from their own expert in my defence.

Nevertheless, I am still able to sell the results of my work, as long as I don't tell you how it works, because there is no evidence that it does. And as such, here I am giving you the hypothesis, because hypothesis is a word that passes the legal hurdle.

The hypothetical interference frequencies are 100MHz and 200MHz which are the centre frequencies of the bands used for transmission of analogue and digital radio broadcasts, which feature highly on the EMC spectrum. There are other interference frequencies - that is obvious - but these two are intentional and available 24/7 from a transmitter near you, and so are quite powerful peppering frequencies close to the fundamental band's central allotted frequencies.

In radio ham'ing, the RSGB teaches that the communications bands have priority over all other equipment. That if communications interfere with domestic equipment, it is the domestic equipment's fault! As licencing authority the RSGB is government linked (more on that later). The radio ham has to be capable of fixing the interference "caused" by the domestic equipment not being up to scratch. Now, that ought to cover interconnects I should think, especially those designed without due care and attention, that are interference "magnets".

So, back to the hypothetical interference at 100MHz and 200MHz. The first quadrant - the antinode - is the moment of maximum energy (assuming current is in phase), and if that can be "transformed" into the return wire - like a power line filter choke - then as it is a short circuit, the interference signal cannot propagate any further.

However, a half turn transformer is not that effective, but perhaps we can expect some attenuation. And that is precisely why the ferrite is placed at a particular distance from the start of the cable.

To calculate the position of the first antinode you need its quarter wavelength in the medium. Here again, there are online calculators often written by hams, for specific cable constructions, and often the formula is given alongside.

There is no VOP% shown for the PVC covering of the average USB printer cable, but there are other sources of values for dielectric constants, from which the VOP% can be calculated.

On the Lautus USB, I decided that the effects of the 100MHz placement could be a case of the cure being worse than the cause - it could compromise the rise and fall times of the digital signal (0's and 1's), so the 200MHz was used alone.

The higher interference-frequency ferrite position is nearer the cable start than the lower frequency would be, due to wavelengths getting shorter the higher in frequency you go.

From that, you should be asking where the signal actually starts. And that is within the source equipment. If it is from the Bitzie using the analogue Lautus cable, the signal source starts at the output transformer which is adjacent the end of the phono plug pin when plugged in.

As for the Lautus USB connected to a desktop, that's a matter of knowing where the source is on the mother board, and you'll need the closest socket.

I believe from memory I set the distance at 8 inches, and so a couple of inches either way might not make much difference, as it is still within the first quadrant.

Hopefully the description above is in easy to follow basic physics and I haven't complicated it with advanced maths. My opinion is if you are able to follow such a description and it makes sense to you, then stuff you simply cannot understand might not pass the smell test.


Edited by Graham Slee - 06 Mar 2022 at 9:40am
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