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Why digital seems to be affected by power and cables

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WireWorld suggest the following re USB Audio... A better USB cable may not help a printer, but it can really improve an audio system.   When a printer receives a file through USB, its error correction fills in any missing information by having the computer resend the file until it is complete.   However, music signals are continuous streams of data that have only one chance to get through a USB cable.   Any missing portions of the music signal cannot be replaced, which is why USB audio cables that preserve more information can dramatically improve sound quality.   The highest fidelity is achieved with a USB cable that preserves the original square shape of digital audio waveforms.   Cables tend to round off those square waves, interfering with the timing of the processor and signal, creating errors known as jitter.   Wireworld USB audio cables utilize unique new designs that minimize jitter by providing squarer waveforms than the standard design used by others.   Providing the squarest waveforms at each price level, they make great improvements in tone quality, clarity, image focus, smoothness and dynamic range.

Is this correct... WireWorld suggests that music signals are continuous streams of data that have only one chance to get through a USB cable?   

 

Any thoughts or is this just rubbish from WireWorld?   If this is the case then it is like SPDIF, probably no better, and perhaps not as good as SPDIF?

Edited by Ping

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Well, after reading through three pages of this thread I felt a strong desire (maybe a need) to say something myself, so I skipped this the last page... and now I am on page twelve. So, not to be deterred, and I do know that I've missed much of the conversation (by skipping forward) and only entertained the embryo, I guess as it were, phase... so what I have to say is that I have nothing to say.

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I'm an idiot, and here I was thinking this thread, "Why digital seems to be affected by power and cables", would be interesting.... 4 pages in I realised it was a pissing match, with no room for assumption, constructive criticism, or opinions (or too much room). Now this thread could have been good. I'll unfollow now.

Edited by rastus

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Sorry you feel that way rastus.  Seems to me it has been a good discussion between those who discern audible differences between cables, and scientific measurements.

 

I don't see it as a pissing match at all.

 

Try pink fish media http://www.pinkfishmedia.net/forum/ or umpteen other audio forums if you really want to see pissing matches.

Edited by CraigS

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Is this correct... WireWorld suggests that music signals are continuous streams of data that have only one chance to get through a USB cable? 

 

That is correct.  There is no error correction in USB audio, unless the manufacturer wrote a custom driver to do so (examples?  none afaik)

 

However, if we look at the USB data, we see that data errors are so exceedingly rare, we should consider that they do not exist.  Somewhat like the case for SPDIF (but even better than SPDIF).

 

However any electrical interference may be transferred through the cable to the converter side, or it can appear like timing problems in the data, which is transferred to the converter side (ie.  jitter).

 

 

Really whether USB audio is any good or not in reality, depends a lot on what happens on the DA converter side of the USB receiver.

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with no room for assumption

 

If we wish to discuss how digital audio and its hardware works, then really there is no room for "assumption".   It isn't some mythical land that nobody understands.   The principles and practicalities are all very well understood by professional people.

 

Debate about "the right answer" being a "pissing match" is an unfortunate view.

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If we wish to discuss how digital audio and its hardware works, then really there is no room for "assumption".   It isn't some mythical land that nobody understands.   The principles and practicalities are all very well understood by professional people.

 

Debate about "the right answer" being a "pissing match" is an unfortunate view.

 

Point taken David, maybe I should have said personal bias instead of assumption. Those first three pages certainly looked... mmmm, argumentative (in a none productive way), without being (how shall I say this)... enjoyable (to me). I guess my issue is that when listening (or reading) I am biased, because either it 'sounds' good, or it doesn't, regardless of what the professional (and laws of physics) people say. But then, I guess I was commenting more so about the way the thread was going (after three pages) rather than the content of the thread, my bad. I withdraw my "pissing match" comment, and replace it with....

 

PS: I was of the understanding that the 'right' answer (engendering a moral perspective) can sometimes not be the 'correct' answer (engendering a more scientific approach), but then throw into that mix a 'personal perspective' and we have one hellova mess. Maybe personal perspective needs to be completely removed from scientific examination. Or should it.

Edited by rastus

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Try pink fish media http://www.pinkfishmedia.net/forum/ or umpteen other audio forums if you really want to see pissing matches.

 

That's my point, I don't want to see a 'pissing match'.

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PS: I was of the understanding that the 'right' answer (engendering a moral perspective) can sometimes not be the 'correct' answer (engendering a more scientific approach), but then throw into that mix a 'personal perspective' and we have one hellova mess. Maybe personal perspective needs to be completely removed from scientific examination. Or should it.

 

Personal perspective isn't "invalid" .... it just that we can sometimes build ideas based on it which aren't justified.  

 

 

"Discussion" can be anything we want, of course ....  but for the on-topic / thread title ..... ie. understanding electronics.... needs to be based on objective repeatable evidence....  otherwise it can't really go anywhere much helpful.     In the worst case, it can lead to completely the wrong conclusions.

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Personal perspective isn't "invalid" .... it just that we can sometimes build ideas based on it which aren't justified.  

 

"Discussion" can be anything we want, of course ....  but for the on-topic / thread title ..... ie. understanding electronics.... needs to be based on objective repeatable evidence....  otherwise it can't really go anywhere much helpful.     In the worst case, it can lead to completely the wrong conclusions.

 

Or true... absolutely, now can you convince my wife of that? Please?

 

OK, I get it... so is there anything in the nine pages I missed that deals with power supplies? Like for instance, LPSU vs SMPSU, or low noise power supplies in general and their effect on sound quality? I know I'm pushing the friendship here, but I am sincere in asking.... if there is, then I'll go read the remaining nine pages to find it myself.

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A little bit ..... but the short answer is you can't learn this stuff easily in the pub.   To understand why digital could be affected by cables and power supplies....   you need to start with electronics textbooks (or pay someone to teach you), and work up from there.

 

 

I think the wisdom I would try to impart to someone looking at this broadly .... is to discard (or at least be particularly careful interpreting) any notion of "everything matters".   The primary job of an electronics/system designer is to quantify what affects what, and to understand where things matter, and where they don't.

 

Digital systems can be extremely robust .... and DA converters can be very sensitive.    If a power cable, or the power supply of your CD transport, is affecting the DAC it is connected to (for example) ....   Then, yes - we could focus on improving the cable or supply in the CD player....  but we can also focus on the DAC, and designing it so it is less affected by the CD player.     The dogma that this (everything matters) can lead to, where we may think that without expensive power cords, or enormous power supplies - that we won't ever get top notch audio --- can ignore much of the landscape.

 

That isn't to say that a big cord or supply is "snakeoil".   Not in the least....  but things aren't alway as obvious as they seem.   Measurement and objectivity can pull back the veil of what is going on......   but it is decidely less fun (honestly) than opinions and listening tests .... and you don't need specific knowledge for the later.

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jitter.

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 A "little bit"... well that's a lot of reading (12 pages - 3 pages = 9 pages) for a little bit.  And I'm fugged then, well and truly. I don't go to the pub, I don't even drink (alcohol). Electronics... now there you've got me, I only just barely passed my Networking degree, them damned numbers really got to me, I had to have counseling for months after completion. I prefer to pay someone FOR a device that I can work with (than to go through all that counseling all over again).

I do tend to believe in the 'all things considered' school of thought, though I would have to say I'm a bit of an 'outsider' (can I say rebel) when it comes to most belief systems, especially when coupled with faith. Not that I'm against faith mind, I prefer to think that faith does indeed have it's context, but maybe not so much when it comes to the laws of physics I guess.

I have noticed that "measurement and objectivity" is one thing, after calibrating my system when I've changed some thing, does seem to take the "fun" of actually enjoying it out of it. While you say one may not "don't need specific knowledge for the later", I would have to say that with these new fan-dangled gadgets we have today that "specific knowledge" is rather a requirement to actually enjoy the "fun" of listening, if you know what I mean. Uh oh, it's off to counseling (again) for me!

PS: I knew as soon as I seen your nickname that I'd like you, I mean who wouldn't like someone that calls themselves "davewantsmoore". I mean that sincerely too. Anyway, I just heard a tree fall in the forest.

 

PS: @@petersv > Is "jitter" a comment, statement, question, or a clinical diagnosis? I'm not asking what jitter is, I'm asking what you mean by it.

Edited by rastus

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It's the answer to the questions proposed - why digital seems to be affected by cables. SPDIF is affected by jitter.

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@@petersv > Oh I see, I thought you could see my facial twitch through the screen, I was going to say... your GOOD!

 

SPDIF being coax and/or optical, for the most part, right? I thought I read somewhere (on another forum maybe) that coax cable did not have the jitter issue that optical does. And, I thought I read somewhere (on another forum maybe) that galvanic isolation assisted with the implementation of said coax to reduce unwanted EMI in the line.

 

I have read about this jitter in optical cables, but I really can't say that I've experienced it in my system (touch wood). Just hope (by faith) that I'm doing something right.

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Jitter most definitely occurs in coax. The dielectric (insulation) absorbs and later releases energy, smearing the rise and fall times of a signal's edge making it difficult to precisely know when a sample starts/finishes. This affects the reconstructed waveform by the dac (url above effectively communicates this in a visual manner). Human hearing is also extremely sensitive to timing errors, hence why master clocks and their accuracy are so vital to high end performance (in sub picoseconds - i.e. Femto clocks).

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To clarify, the main difference between TOSLINK (optical) and coax in their source of jitter distortion is slightly different. With optical, most of jitter occurs from the component converting the electrical signal to light and vice versa, with coax this process doesn't occur at all since it's already in the appropriate form (electrical), the distortion there mainly deriving from the dielectric (insulation) smearing the signal edge).

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I've got ears, I'm good.

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I maintain that I could build three cables of the same length and terminated in the same connectors - and provided the cable is 75 ohms you will not hear a difference.  The three would be PTFE, polythene and foamed polythene.

 

The hint is that foamed polythene is used for Digital TV, and that is broadcast from 500MHz to 1GHz (about - round numbers quoted).  You don't see any evidence of dielectric smearing on your digital TV even with ten metres or more between your rooftop antenna and the tele.  Even back in the days of analogue TV, any frequency dependent phase distortion in the cable would show up as colour errors, which also didn't happen (well, they did - but it wasn't the cable, it was multipath errors or some such).

 

If I get around to it I'll do some real world measurements to support that assertion.

 

Now that is not to say that you don't get pulse distortion on coax cables, but resistive losses through skin effect tend to dominate dielectric effects, and only when you have many, many tens of metres of cable, and you are measuring in the nanosecond regime.  With a metre of coax I reckon it is insignificant for SPDIF.  Give me a few days and I'l back that up with measurements.

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why?

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OK Peter, I did read that link... so jitter is uneven distances between the transitions ("Notice that the distance between the transitions is uneven – this is jitter.") So, just like networking, music data signals have 'packets' (word vs network data packets).... personal note: with network data packets, there is always error checking in place to make sure the correct data packet has arrived (otherwise it is re-sent), but with music 'words' there is no error checking? With network data that would be horrendous! So with music this causes "uneven intervals", is this correct? And this "uneven intervals" and "unevenness" causes "distorsion into the waveform". And, if "jitter gets into our D-to-A stage, it degrades the playback." So, if the "original digital recording is intact" (DER!) what we have to do is "remove the jitter or get a better D-to-A converter to resolve the issue." So that's for play back.

How do we remove the jitter, if we haven't got a 'better' DAC?

But with recording, if "jitter gets into the A-to-D stage, those errors are 'baked into' the digital data" and there’s "no recovering the original waveform." Well DER @ that! I'm not recording so all I have to worry about is if the music source is free from jitter. Downloading music from non-reputable sources is a bad, bad, thing rastus! Or could be, if not recorded correctly. That's why they list the equipment they recorded the album on... ahhh. Note: pay money for good sources!

So, the Raspberry Pi, with PiFi DAC+ using I2S transfer... how does this way up? Yes, I already know the answer, I do read.

 

Edit: Would it be better to not use a DAC hat on the Raspberry Pi, just use a DIGI transport (coax or optical) out to an external DAC, or use USB out to an external DAC?

Edited by rastus

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