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Ethernet system for Audio: Tweaks on the clean side


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Someone posted Hans' measurements video and the audiophile style links on the Roon Community yesterday. I only got around to watching the video in full today and I'm sad to say that's another 13 minutes of my life wasted.....

 

How anyone can measure clock jitter at the DAC master clock pin and correlate that to subjective listening impressions is beyond me.

 

Alex Crespi's post is a load of pseudo-scientific testiculating and Swenson's post is, as you say, nonsensical.

 

The only place the effects of clock deviation can be measured is at the output of a DAC.

 

To date, no one has produced any evidence of measured differences at the DAC output due to fancy clocks, ethernet switches, cables, or the EtherREGEN.

 

Until such time as they do, I remain healthily skeptical.

Edited by The Mad Scientist
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7 hours ago, March Audio said:

Trying to measure the jitter with a probe close to the clock gives you no direct indication of what the jitter is in the actual audio output signal.

Exactly.

 

Measuring jitter somewhere within the system, is fine.... but it needs to be compared to the output so you can make an analysis as to if it is the cause of distortion in the output.

This is pretty basic stuff.

 

What makes it more perplexing, is that if you (actually!) have the ability to measure "jitter" somewhere within a digital system accurately (really) .... then you have a pretty good measurement system and know how to use it....  so comparing it to the output signal is trivial.

 

The scenario where you have some distortion in the output.... but you could never measure/find/link the "jitter" in the digital side of the system to it..... is quite common/normal.

 

But .... the scenario where you are able to accurately/directly measure jitter on the digital side..... but you can't (don't?!) measure the analogue side, and can't analyse how the jitter corresponds to the analogue output.    Very "strange" as to why you wouldn't do this.

 

 

 

Much smaller and fleeting distortion in the analogue audio signal might be (more) audible, than some people think .....  but these can be shown.    They're not something "we don't know about", or "don't have the capability to measure".   At the risk of saying something divisive.... I think the only reasonable things to conclude generally is that the people doing tests like this, either:

 

  1. Really honestly don't understand what they're doing..... but just "do stuff, and show the world anyways" (don't they fear being embarrassed? ... or?)
  2. Can't demonstrate the differences they set out to demonstrate (eg. a range in the audio output) .... but feel compelled to "do something, to show their audience something" (even if it's weapons-grade woo-woo)
  3. Are just doing what they think people expect (or will accept) them to do (ie. this is just how we do it, because that's just how people do it) ... ie. "this is the type of video our audience wants/expects" is the primary driver of "what to do".
  4. Are being intentionally misleading

... or some combination.

 

I don't think #4 is particularly likely.... and I think #1 is also unlikely to be a complete explanation.

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1 hour ago, The Mad Scientist said:

How anyone can measure clock jitter at the DAC master clock pin and correlate that to subjective listening impressions is beyond me.

 

You could do this.... but without measurements and analysis of the audio output... then it's hard to say much conclusive about it.

 

If the audio outputs measured different .... then you could make a hypothesis (or even perhaps draw a conclusion) about the jitter relationship to the different subjective results.

vs

If the audio outputs measured identically .... and the testing was sighted .... then it would be a long bow to draw, to make a conclusion about the jitter relationship to the subjective results.

 

It's just simple basic high-school science on how to analyse the method and results of an experiment, and what conclusions you can (really) draw based on what you did/got.

 

1 hour ago, The Mad Scientist said:

To date, no one has produced any evidence of measured differences at the DAC output due to fancy clocks

 

You can get differences in DA output, through changes in the DA clock.

 

Further back in the chain of digital data.... then it becomes much less likely... but even so, it still happens.   For example, consider an imperfect "reclocker", that feeds a clock/converter.   It is not immune to the incoming digital signal, this is especially common with low frequency jitter, where you see a spreading of the "base" of a tone.

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25 minutes ago, davewantsmoore said:

 

2 hours ago, The Mad Scientist said:

To date, no one has produced any evidence of measured differences at the DAC output due to fancy clocks

 

You can get differences in DA output, through changes in the DA clock.

 

Sorry Dave, I should have been more specific. I meant to say that no one has produced measurements at the DAC output relating to jitter which surpass the threshold of audibility.

Edited by The Mad Scientist
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On 13/12/2021 at 8:52 PM, Thunder_Snake said:
On 13/12/2021 at 7:23 PM, Stereophilus said:

Yes and no… the “ritual” of vinyl is said to be part of the allure.  It is at odds with the allure of digital, which is quick and convenient.

And this is my argument, the allure of what once was simple, convenient digital ie. a CD player, or a transport and Dac is now becoming convoluted by so many variables and doodads (implied in this thread at least), that was once quick and easy is now a moot point.

Don’t get me wrong, I have put time and thought into my digital rig, and I do believe switches, power supplies, cables etc. do make a difference. Alas the initial convenience and simplicity of digital playback that was the catalyst for most of us setting up a fine digital chain (me included), is now gone.

 

This development in audiophile viewpoint seems to be associated with a belief that nothing can be gained other than through hard work and major expenditure.  The suggestion that technological advance can result in pristine audio source quality being obtainable simply and cheaply is rejected as too good to be true.

 

The difficulty for this audiophile viewpoint arises when the alleged defects in digital source sound quality are asked to be demonstrated:-  

 

18 hours ago, frednork said:

Anyhow, heres the vid. Have at it.  Perhaps another small step to finding the measured "proof" that some seem to require.

 

As has been pointed out, the more relevant measurement would be of the analogue output signal.

 

However even those measurements would not be all that significant unless it could be shown that the measured imperfections in the analogue output signal actually rose to the level of being audible for human hearing.  We are not listening machines or gods; we are but flesh and blood.

 

*   *   *

 

On a related topic, if clock phase noise is so critically important for a DAC used in the home listening room (as suggested in the video), where are the reviews of phase noise in the clocking for the ADCs used in recording studios?  Which model recording studio ADCs are recommended by audiophiles?

 

What of studio recordings made 30 years ago?  Are they steeped in audible adverse effects from clock noise? Are such defects audible for the ears of a trained listener?

 

I do not expect answers to these questions as we see nothing posted about recording studio ADCs.  It is all about allegedly audible defects in domestic DACs.

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56 minutes ago, MLXXX said:

On a related topic, if clock phase noise is so critically important for a DAC used in the home list


Let’s blame this as the cause of our SQ differences,  

 

regardless of what “noise “ is in the digital transmission,  digital inputs only look at 90% of the rise or fall of that edge for a cycle and ignore everything else.   Now you need a lot of “noise” to interrupt transmission.

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1 hour ago, MLXXX said:

What of studio recordings made 30 years ago?  Are they steeped in audible adverse effects from clock noise? Are such defects audible for the ears of a trained listener?

 

Yes, what do people really think of them?   I have many digitally recorded classical vinyl records and CDs, going back to the 70s.      I think they sound excellent btw.

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1 hour ago, MLXXX said:

 

 

On a related topic, if clock phase noise is so critically important for a DAC used in the home listening room (as suggested in the video), where are the reviews of phase noise in the clocking for the ADCs used in recording studios?  Which model recording studio ADCs are recommended by audiophiles?

 

What of studio recordings made 30 years ago?  Are they steeped in audible adverse effects from clock noise? Are such defects audible for the ears of a trained listener?

 

I do not expect answers to these questions as we see nothing posted about recording studio ADCs.  It is all about allegedly audible defects in domestic DACs.

You guys are driving this discussion off topic. But you are wrong and it's just an sloppy appeal to authority.

Professional sound engineers do pay attention to this stuff. 

 

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13 minutes ago, Deepthought said:

I can feel a bit of ad hominem coming on.

 

People should be very wary of taking these youtubers seriously.

 

the test is incompetent.  The Alpha Audio test has been discussed elsewhere so I won't rehash.

 

Hans just takes it as gospel and regurgitates it because he doesn't understand the technicalities. He uses sighted testing and presents it as subjective fact.

 

Swensons statements are not based in fact.  Plain wrong. We can easily measure jitter in audio signals.

 

It's not ad hominem to expose these things.

Edited by March Audio
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29 minutes ago, aussievintage said:

 

Yes, what do people really think of them?   I have many digitally recorded classical vinyl records and CDs, going back to the 70s.      I think they sound excellent btw.

 

 I cannot be sure of the performance of recording studio ADCs of the 1970s.  I suspect there could have been some room for audible improvement at that early stage in the use of digital technology for audio.  

 

However certainly by the final years  of the 20th century, ADC technology was quite mature.  At that time, it would have been routine engineering to design studio ADCs for excellent audio performance for human hearing, with specs sufficiently good to achieve that.   There would have been no need to over-engineer, by chasing femtosecond clock stability.

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2 hours ago, The Mad Scientist said:

I meant to say that no one has produced measurements at the DAC output relating to jitter which surpass the threshold of audibility.

Sure.

 

I don't know about that..... you might be right.... but this tends to charge down the path of "all DACs sound identical" (assuming flat frequency response, etc. etc.).    I think there's plenty of people who are (rightly or wrongly) broadly unwilling to accept this....  and I think to charge off down that path is in danger of missing (or not focussing on) the point (the very important point).

  1. Show me the analogue output.
  2. Point to me the bits in the output that you say the jitter caused.
  3. Give me some sort of argument about how you think the jitter did that....  ideally by changing the jitter and changing the analogue output.
  4. Do some listening tests.
  5. Draw a conclusion which says (something like) "the jitter affects the audio signal, and the change in the audio signal is audible".

 

To fail at step 1 or 2... is a fail.

To skip step 1 and 2.... then vague step #3, and go right to #4.    Is not a "this could be improved" moment.... it's a "shouldn't you be embarrassed" or a "are you taking the mickey?! type of moment.

To go right to #3 and #4 .... and do #4 ignoring the problems of those tests (sighted, etc.) .... is just absurd.

 

 

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50 minutes ago, davewantsmoore said:

I don't know about that..... you might be right.... but this tends to charge down the path of "all DACs sound identical" (assuming flat frequency response, etc. etc.).

 

Im not sure  that we can make that leap, and I dont think many people really do take that attitude.  There can be a number of reasons why one DAC may sound different to another.  I think what @The Mad Scientist meant was that no one has been able to provide measurements at a dac output that jitter caused by a network switch has been shown to exceed the level of audibility.  I would go one further and say no-one has been able to show *any* appreciable effect on jitter in the audio output due to a network switch.  Least of which the manufacturers of said audiophile switches.

 

50 minutes ago, davewantsmoore said:

To go right to #3 and #4 .... and do #4 ignoring the problems of those tests (sighted, etc.) .... is just absurd.

 

This is absolutely the point.  Its a solution looking for a problem. The cart has been put before the horse.  No one has been able to demonstrate there is actually a problem to solve.  Without doing so first its impossible to design a solution.  You need to establish cause and effect.  So, its just a theory.  A theory that no one appears to be able to demonstrate works, neither technically or subjectively.  Both of which is actually relatively easy to do.

 

As such, the theory has been demonstrated to be incorrect.

 

Edited by March Audio
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22 minutes ago, Deepthought said:

 

Posts on audio ADC performance do exist as you have demonstrated. [It's a while since I had visited that particular forum: "Gearspace! This forum is a destination for the friendly and helpful sharing of information about audio recording and production techniques, the use of recording equipment and experiences in the world of music, audio, post-production and more.".]

 

As I mentioned earlier today, I don't think we can assume that the issue recently raised in this thread of clock phase noise in the DAC can be divorced from the issue of potential clock phase noise in the ADC or ADCs that were used in the recording process.   If clock phase noise really is audible in modern DACs,  or at least is liable to become audible, we would need to be very concerned with what technology was used for making the recordings we listen to, whether the capture of the analogue microphone signals was done with modern ADCs or with older ADCs, as they could also potentially be affected.  We don't see such discussion on this forum of the effect of clock phase noise in recordings (at least, not that I have noticed).

 

1 hour ago, Deepthought said:

Professional sound engineers do pay attention to this stuff. 

 

Do they get concerned with ADC clock phase noise?

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1 hour ago, March Audio said:

Im not sure  that we can make that leap, and I dont think many people really do take that attitude. 

I don't know.   I think a lot of people hear statements like "nobody has ever shown measurements of an analogue output, that was caused by jitter, that passed the threshold of audibility"

... and take it to mean that "jitter is inaudible".

 

There are lots of people in lots of places making the claim that "jitter is not a factor in the sound of devices" (or something similar to that).

... and that might actually be true, or at least a very very good generalisation, but.

 

Even if the above it true when we add the caveat of "jitter caused by a network switch"..... All I'm saying, is anyone who wants to say it does, can show it.

 

1 hour ago, March Audio said:

no-one has been able to show *any* appreciable effect on jitter in the audio output due to a network switch.

Yes.

 

Even showing something, even something which you would not expect to be audible.... just some difference, would be something.

 

If you showed something tiny, then I would say you better be measuring very carefully, and you better be running the listening tests as a real tight ship.

... but if you can show nothing, then 0_o

 

57 minutes ago, MLXXX said:

Do they get concerned with ADC clock phase noise?

They're routinely interested in the performance of their equipment....  <shrug>

Some might make the same mistakes as some audiophiles.... some not.

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16 minutes ago, davewantsmoore said:

... and take it to mean that "jitter is inaudible".

 

Jitter levels in modern well designed DACs are well below audibility, so that statement is correct when taken in the correct context.  It really is a solved problem and has been for some years.

 

16 minutes ago, davewantsmoore said:

All I'm saying, is anyone who wants to say it does, can show it.

 

Yes, absolutely.  No magic going on here.  If its there it can easily be seen/measured and quantified if audible or not.

 

 

Edited by March Audio
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51 minutes ago, March Audio said:

Jitter levels in modern well designed DACs are well below audibility, so that statement is correct when taken in the correct context.  It really is a solved problem and has been for some years.

Indeed.

 

I'm just coming at it from the other angle.... which I think is usually more helpful in a context like this thread, or audio-people stuff in general.   I don't need to make any statements about jitter, etc.... except to say that I will look at a valid test, or criticise an invalid test ... and if you can (really) show things about jitter then many serious people will be very interested.

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