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Investigation Into Effects Of PC load On DAC Analogue Output

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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.

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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.

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Just for info here is some info on galvanic isolation from Mathias Carstens who is the founder of RME.


Hello Mr. Stämmler,

the isolator arrived this morning. I tested it right away:

- It’s fully compatible with all RME USB interfaces, regardless of whether they’re working in interrupt or isochronous modes. The test was carried out with the maximum channel count. Also, I've flashed the device with a new firmware via USB. No problem at all.

- The power supplied to the device end is surprisingly high. Our bus-powered interfaces Babyface and Babyface Pro overload the isolator anyway, so you’ll have to work with it there on an external power supply. This was to be expected, because at 550 and 800 mA we’re drawing considerably more power than originally planned of course.

- The isolator does exactly what I had hoped it would: it eliminates all problems arising via USB during unbalanced test setup.

I’ve attached two screenshots for you. Two USB audio interfaces were connected to a notebook here (one wasn’t from RME). On one device the analysis software emitted a test signal (1 kHz sine wave), on the other device it was analyzed at the input. The analog connection Out to In is unbalanced. Once with the isolator, once without.

I’ll share this information and the images with you. So if you want to show somewhere that RME has found the isolator to be fully compatible, or want to use the measurements on the website or as visual aids in your presentations, then you’re welcome to do so free of charge.

Best regards,

Matthias Carstens





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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.?)

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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.

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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.

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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.

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More data.  Same PC and ADC.  This time a Gustard X16 DAC driven from Roon with WASAPI through XLR outputs.


No PC load.  Note a very small amount of mains pick up at 50Hz, 150Hz and 250Hz.  From the weight this DAC has a linear psu internally with a transformer.  Probably from that.




With PC loaded.



No significant difference.


I will perform the Deltawave check on this DAC tomorrow.  I can also try the DACs RCA single ended output.


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