Investigation Into Effects Of PC load On DAC Analogue Output

[PeterSt]

1 minute ago, March Audio said:

Well for one thing it might help people implement proper fixes instead of blindly flailing around in the dark.

 

Do you have an example of such a fix ? ... just to know what we are (both) talking about.

[March Audio]

4 minutes ago, PeterSt said:

 

Do you have an example of such a fix ? ... just to know what we are (both) talking about.

Dacs can be isolated from the source.  See the post earlier in the thread with the quote from the founder of RME.

[manisandher]

17 minutes ago, March Audio said:

With respect you are entering the territory of "I hear it therefore it is", which is not what an objective thread is about.

 

I give up.

[March Audio]

26 minutes ago, PeterSt said:

 

Again accepted. But how do you know beforehand that you can measure audible differences ?

Well, you assert that jitter is an audible problem here.  Have you considered the research on audibility of jitter?  Its easily measurable and has been subjectively correlated to audibility,

 

From J Dunn again

 

[PeterSt]

30 minutes ago, March Audio said:

Dacs can be isolated from the source.  See the post earlier in the thread with the quote from the founder of RME.

 

OK, thanks. But are you then saying that if the DAC is not isolated from the source, the playback software can influence the sound while all remains bit perfect as such ?

[March Audio]

33 minutes ago, manisandher said:

 

I give up.

This is why you cant use a mic in a room to look for subtle differences.  How do you separate out the highly variable background noise?

 

 

 

 

[March Audio]

8 minutes ago, PeterSt said:

 

OK, thanks. But are you then saying that if the DAC is not isolated from the source, the playback software can influence the sound while all remains bit perfect as such ?

Not from what I have seen.  The PC doesnt stop causing the problem just because you have disabled a few minor processes.

[PeterSt]

6 minutes ago, March Audio said:

Not from what I have seen.  The PC doesnt stop causing the problem just because you have disabled a few minor processes.

 

Isn't this putting things upside down (for answers) ? So the PC is causing problems "as such" you say ? (this is not completely clear to me now).

Put differently (my words derived from your ideas): the problems with SQ are there, but they are or are not caused by playback software ? or cured for that matter ?

 

6 minutes ago, March Audio said:

because you have disabled a few minor processes.

 

Disabled ?

 

[idiot_savant]

@PeterSt - maybe it would be helpful if you could describe the interface used within your tests? i.e. how is the DAC connected and powered? I believe ( happy to be corrected on this ) that @March Audio is using a DAC that is connected via USB with an asynchronous style interface, and is powered separately from the PC.

 

If your tests were using, for example a synchronous interface, or USB in adaptive mode, or the DAC is somehow powered by the PC, this might give us some insight?

 

 

your friendly neighbourhood idiot

 

[PeterSt]

 

hahahahahahaha ... so this is what we are working with anno 2021 ?

You know that is from the age that we could call jitter just as well (tt) wow, right ? Wasn't the CD just 10 years new, there ?

 

Anyway, if we take it for granted that RMS jitter under 20ns won't be audible, then I wonder what I am doing here. We could also wonder what everybody is doing everywhere.

I should also revisit RME's specs with you saying it's all right, because I recall that RME isn't the best at all for jitter specs and I think I read similarly (hints to it) in the manual.

 

I am done in this thread. Waste of time. The goal of it also can't be made clear.

 

1 hour ago, March Audio said:

My tone has been entirely civil.

 

Belittling civil, yes.

[March Audio]

21 minutes ago, PeterSt said:

 

Isn't this putting things upside down (for answers) ? So the PC is causing problems "as such" you say ? (this is not completely clear to me now).

Put differently (my words derived from your ideas): the problems with SQ are there, but they are or are not caused by playback software ? or cured for that matter ?

 

 

Disabled ?

 

As idiot_savant alluded to, and I expanded upon early in the the thread, it's not a virtue for a DAC to be sensitive to PC activity.  Quite the opposite in fact.

 

PCs are noisy, that's a given.  It's the way they are.  Theycarecalso very variable in this respect.  So this should be a paramount consideration in a dac design to be insensitive to this.

 

As we have seen in this thread, it's quite possible to engineer dacs that are insensitive to these issues.

 

At the risk of being somewhat facetious, I would say to anyone who hears these alleged improvements from "tweaking", what's wrong with the design of your dac?  Can't be very good if it can't deal with this. 😉

 

Somehow has it backwards?

[March Audio]

20 minutes ago, PeterSt said:

 

hahahahahahaha ... so this is what we are working with anno 2021 ?

You know that is from the age that we could call jitter just as well (tt) wow, right ? Wasn't the CD just 10 years new, there ?

 

Anyway, if we take it for granted that RMS jitter under 20ns won't be audible, then I wonder what I am doing here. We could also wonder what everybody is doing everywhere.

I should also revisit RME's specs with you saying it's all right, because I recall that RME isn't the best at all for jitter specs and I think I read similarly (hints to it) in the manual.

 

I am done in this thread. Waste of time. The goal of it also can't be made clear.

 

 

Belittling civil, yes.

I am not clear on what you are saying.  Are you saying that the scientific research is wrong and you know better?

[March Audio]

29 minutes ago, PeterSt said:

 

Anyway, if we take it for granted that RMS jitter under 20ns won't be audible, then I wonder what I am doing here. We could also wonder what everybody is doing everywhere.

I should also revisit RME's specs with you saying it's all right, because I recall that RME isn't the best at all for jitter specs and I think I read similarly (hints to it) in the manual.

 

I am done in this thread. Waste of time. The goal of it also can't be made clear.

 

 

Belittling civil, yes.

Jitter audibility is dependant on its spectrum and frequency.

 

If the RME jitter performance was poor it would show in the plots.

 

The goal of the thread is quite clear; to investigate the impact of PC load on dac output.

 

I'm sorry but you didn't appear to know some jitter fundamentals, I'm sorry the information provided was considered unhelpful.

[pkane2001]

47 minutes ago, PeterSt said:

hahahahahahaha ... so this is what we are working with anno 2021 ?

You know that is from the age that we could call jitter just as well (tt) wow, right ? Wasn't the CD just 10 years new, there ?

 

Anyway, if we take it for granted that RMS jitter under 20ns won't be audible, then I wonder what I am doing here. We could also wonder what everybody is doing everywhere.

 

Yes, we're working with 1990's jitter research. Dunn published his first paper in 1992 and the math is still correct. In other news, we are also using the Fourier theorem first published in 1882, scary, right? ;) 

 

Here's part of a conclusion from a 2005 study on jitter audibility (nano-seconds, not pico-seconds threshold). Note that there are a number of references to other studies that show similar results:

 

 

This was using music as the test material with the listener being able to chose their own track using random jitter. On specialized test signals with different types of jitter, as mentioned above, the threshold can be lower, but still in the nano-seconds range.

 

 

[March Audio]

1 hour ago, idiot_savant said:

@PeterSt - maybe it would be helpful if you could describe the interface used within your tests? i.e. how is the DAC connected and powered? I believe ( happy to be corrected on this ) that @March Audio is using a DAC that is connected via USB with an asynchronous style interface, and is powered separately from the PC.

 

If your tests were using, for example a synchronous interface, or USB in adaptive mode, or the DAC is somehow powered by the PC, this might give us some insight?

 

 

your friendly neighbourhood idiot

 

Yes, there are many potential sources of problems.  Understanding the issues in any particular set up is important.  It's no good blaming the PC for jitter if it's a synchronous connection.

[botrytis]

3 hours ago, PeterSt said:

 

They are - trust me (no you won't).

So what is the reason for this thread again ?

 

Edit: this crossed with your post above.

 

Have you heard the old saying, 'Trust but Verify?'  If one can't measure it, is it really there? Again, it can be a part of expectation bias.

[botrytis]

1 hour ago, pkane2001 said:

 

Yes, we're working with 1990's jitter research. Dunn published his first paper in 1992 and the math is still correct. In other news, we are also using the Fourier theorem first published in 1882, scary, right? ;) 

 

Here's part of a conclusion from a 2005 study on jitter audibility (nano-seconds, not pico-seconds threshold). Note that there are a number of references to other studies that show similar results:

 

 

This was using music as the test material with the listener being able to chose their own track using random jitter. On specialized test signals with different types of jitter, as mentioned above, the threshold can be lower, but still in the nano-seconds range.

 

 

 

We also have to take into account what OUR ears and brain can audibly detect. I will give sight and computer monitors as an example (for gaming). With our eyes and biochemical wiring, the max frames per second we can discern is 60 fps. Anything over that, it seems it really doesn't matter. But people like getting the monitors that can handle over 60 fps. It kind of reminds me of the scene in the movie, 'This is Spinal Tap'. Again, expectation bias.....

 

[Summit]

5 hours ago, March Audio said:

I cant edit my posts now I have admin control haha.  I meant to add to the above that, with respect, I dont accept that its beyond question that bit identical sources can sound different.  I will caveat that statement because it requires expanding.

 

Can DACs be affected by whats happening up stream?  Yes.  Already discussed ground loops, noise currents etc.  However good dacs are not sensitive to this. So its a secondary effect, not that of identical data sounding different.

 

Are you absolutely sure that it is indeed desirable that a DAC is very insensitive to noise on the signal input? Serious and fundamental question.

 

Context: There is always a great risk that in order to become completely insensitive to noise, extra circuits such as galvanic insulation are needed. Some think that step analogue filters, GI etc. can have a devastated effect on SQ and that it is bigger than the advantage they have on reducing noise, which often are already very low, at least if feed from a low noise source. The negative effects is caused because those filter/GI etc. function by preventing electrons from flowing directly between two points. Typical the sound can sound less direct, less exiting, less transparent and softer.

 

Best not to pollute in the first place, instead of trying to fix it later .

[Racerxnet]

1 hour ago, Summit said:

 

Are you absolutely sure that it is indeed desirable that a DAC is very insensitive to noise on the signal input? Serious and fundamental question.

 

Context: There is always a great risk that in order to become completely insensitive to noise, extra circuits such as galvanic insulation are needed. Some think that step analogue filters, GI etc. can have a devastated effect on SQ and that it is bigger than the advantage they have on reducing noise, which often are already very low, at least if feed from a low noise source. The negative effects is caused because those filter/GI etc. function by preventing electrons from flowing directly between two points. Typical the sound can sound less direct, less exiting, less transparent and softer.

 

Best not to pollute in the first place, instead of trying to fix it later .

So people daisy chain a bunch of gadgets in the hopes of cleanimg up the signal before the DAC. 

[idiot_savant]

@Summit - nobody is suggesting that deliberately ignoring PC noise is desirable, but you have to consider a fundamental point here - we’re not trying to stop noise getting out of the DAC using filters. Surely in an ideal DAC, the electrons that represent the digital samples have *can’t* get to the analogue out? The whole point of digital electronics is its an abstraction - I.e. as long as the samples get to what needs them in time, it’s completely irrelevant how they get there - paper tape, punched cards, Ethernet, USB, a really fast typist. 
 

your friendly neighbourhood idiot 

[Summit]

1 hour ago, Racerxnet said:

So people daisy chain a bunch of gadgets in the hopes of cleanimg up the signal before the DAC. 

 

Yes many try to clean up the signal instead of preventing the signal from getting polluted.

[idiot_savant]

Polluted with what?

 

 

 

your friendly neighbourhood idiot 

[Summit]

1 hour ago, idiot_savant said:

@Summit - nobody is suggesting that deliberately ignoring PC noise is desirable, but you have to consider a fundamental point here - we’re not trying to stop noise getting out of the DAC using filters. Surely in an ideal DAC, the electrons that represent the digital samples have *can’t* get to the analogue out? The whole point of digital electronics is its an abstraction - I.e. as long as the samples get to what needs them in time, it’s completely irrelevant how they get there - paper tape, punched cards, Ethernet, USB, a really fast typist. 
 

your friendly neighbourhood idiot 

 

Most manufactures are indeed trying to stop noise from getting both in and out of the DAC using filters and galvanic isolation. GI can be done with transformers or optocouplers, but it’s not perfect since there is always very small amount of capacitance between two sides of galvanic isolation which allowing very high frequencies to pass thru. Another (IMO better) way is to reduce noise on the source.

[Summit]

2 minutes ago, idiot_savant said:

Polluted with what?

 

 

 

your friendly neighbourhood idiot 

 

Are you serious? Noise, jitter, FN, RFI, EMI etc etc.

[idiot_savant]

Right, so where is this pollution on the measurements provided? @March Audio hasn’t taken any outrageous measures, so maybe we’re worrying about nothing?

 

When you say signal is polluted with jitter etc do you mean the samples are corrupted somehow? Delivered at the wrong time?

 

I’m genuinely interested - “signal” could be the actual audio samples, or the USB packets, or the output from the DAC itself

 

 

your friendly neighbourhood idiot