Investigation Into Effects Of PC load On DAC Analogue Output

[SoundAndMotion]

2 hours ago, March Audio said:

So to conclude, with this PC, load makes no significant measurable difference to this DACs performance.

 

Please note that these tests do not account for other potential issues that may be encountered such as ground loops in single ended RCA systems.

Bold added.

 

Thanks for your efforts.

 

So now I can conclude that some computers with some DACs do show measurable activity-related noise (I'll find links, if anyone is interested), but not all (as you've shown)!

 

Edit: Here are a couple examples:

"Computer Activity Can Impact DAC Performance"

"Budget DAC Review: Schiit Modi 2 ($99)" - Here one also sees how an ISO Regen cleans it up.

both on ASR. Will create pseudo-links, if needed.

[SoundAndMotion]

4 minutes ago, March Audio said:

However to be clear this isnt an issue of "the PC activity" causing noise as I am discussing above.  Its a connection issue.

It seems to be activity related. Sure, ground loop, but still activity related ground currents.

Edit: Yes, I added that the ISO Regen improved the signal.

[SoundAndMotion]

2 minutes ago, March Audio said:

No its not. Its a problem created by a problematic way of connecting equipment together.

I guess you didn't read it. Same connection, different software made the problem disappear.

[SoundAndMotion]

I guess search doesn't work on your computer.

 

https://www.audio"science"review/forum/index.php?threads/computer-activity-can-impact-dac-performance.22/

[SoundAndMotion]

The OP shows it's software related. 

 

If you hadn't read it, why say with such certainty that it's not software?

[SoundAndMotion]

You've missed the point. I already mentioned that the ISO Regen improved the results, so galvanic isolation can block the noise. But changing the software, also changed the noise! So it appears the noise is generated by the computer activity and it travels along the connection. It's activity AND connection, not OR.

 

And you were still willing to state your opinion (in Objective-Fi?) without investigation of the other measurements.

And we don't know all the details of Amir's test. Good point. Do we know all those details from your post? (Direct sound, wasapi etc.?)

[SoundAndMotion]

What Amir and you say is less important than what's in the data. The noise changed when he changed software. What is the source of the noise? Grounding problems allow noise into places it shouldn't be, but what is the source of the noise?

You need not continue hunting down a single problem, and then announcing success, when clearly multiple problems exist. Activity AND connection. Not OR.

[SoundAndMotion]

As I understand it, the raisin d'être for this thread is given here:

3 hours ago, March Audio said:

Prompted by discussion in another thread I decided to take a look at the effects of PC load on a DAC analogue output.  The assertion is that PC load (CPU/Disk etc) increases noise in the DAC output. The assertion doesnt specify what type of noise or how this noise manifests, so I will be looking for any differences in a DAC output between an unloaded PC at idle (baseline activity), and when at 100% CPU load with disk read/write activity.  This is going to be purely a measurement based exercise and not using subjective listening.

and here:

 

And I believe you have begun to convincingly demonstrate that those who "hear differences" where you believe they can't, likely won't...  with your computer and your software/configuration choices and your hardware/DAC.

But your goal cannot be achieved with your single setup. Indeed, trying multiple setups, one at a time is very inefficient. IMHO, you can achieve your goal much more efficiently by convincing those who claim to hear a difference to replicate your effort above, or a similar measurement-oriented approach. Many will beg off, but if you convince only one or two, you'll be further along toward your goal than testing one setup, then another, then another... 

All this assumes I understand your goal.

[SoundAndMotion]

Those of us who use measurements to convince people who don't want to agree with us use different methods than those who want to "convince" people who already agree with them, aka preaching to the choir. I welcome colleagues' criticisms and use them to improve convincingness, not to criticize their comments.

Many people don't like this fact: failure to reject the null hypothesis does not prove the null hypothesis (i.e., no audible difference). Absence of evidence is not evidence of absence, and all that... especially to those who don't believe the absence (of an audible difference).

I'm not arguing that those who "hear differences" actually hear what they claim, in fact I'm quite skeptical, I'm arguing that if you want to convince skeptics, the methods must reflect that.

As a child I could always find earthworms under big rocks in our yard. That does not mean you'll find any if you look under one rock where you live, even dozens or hundreds of rocks. That does not negate my experience. Although I've read what @March Audio wrote, he seems to not read my posts. I think his effort serves as a great template to encourage others (especially those who "hear") to follow, but the plan to repeat the measurement N times may not uncover his desired worms.

 

This is @March Audio's thread, so if he wants to suppress views that don't support his, that speaks to his motives more than my posts.

[SoundAndMotion]

2 hours ago, firedog said:

Maybe you didn't read the whole thing at ASR or the other threads on the topic. The point was the ISO Regen lessened the noise, but only with a DAC that is essentially "broken" b/c of improper design. With other DACs it made no difference. 

Same for other DACs - except for a small minority that are improperly designed, March Audio's results hold. Conclusion: the PC doesn't matter for these measurements, unless you have a DAC that is inherently defective. 

Archimago did similar testing at his site a while back and got the same results. 

The whole thing? If you mean the whole 2 page thread, I did. And other DAC threads too. Did you? Amir made assumptions: he didn't locate the noise source; he read the brochure which said "isolated", but not "galvanically isolated", so he assumed it was defective. It may be, but I don't accept that type of assumption without evidence.

 

There is a common technique of stating that all "competent" or "properly-designed" DACs behave [the way you say - whatever you want], with the convenient response to any counterexample as being "broken" or "defective". You're guaranteed to always be right, since you made the definitions.
There was a $1000 bet on another site (not the recent one on ASR), where the person proposing the bet would allow the I-can-hear-a-difference claimant to pick any 2 "competent" DACs. He warned of DACs that were deliberately or unintentionally "defective". He said pick any 2 that had been tested with SINADs over "say... 100dB". I noticed that of the many DACs that Amir had tested, the median was about 100. So by the challenger's admittedly random cutoff, nearly half the DACs tested were defective. You didn't make that bet, but I wonder how useful a term like "defective" is if it applies to too many examples. The rule-of-thumb that's intended to use it may be weak, maybe a rule-of-pinkie.

 

The fact is that a "defective" DAC may function well with a low-noise PC, as will a "competent" DAC with a noisy, but within spec, PC. What about PCs that are nearly in spec, but not quite (noise on USB lines slightly too high)?

 

@March Audio has shown that his PC with (now 2) DACs performs certain tests well. Great, and I appreciate his effort. My concern is that if the goal is to convince members who "hear a difference" in whatever (don't think the motivating threads were simply about DACs), or to convince them they have defective hardware, this method may not work. And there are better, more efficient, methods. @firedog do you think this can convince the target group? I don't think convincing people who are already convinced was the goal. I do not wish to dissuade @March Audio from continuing... so I'll probably continue with the issue of convincing skeptical people in another thread.