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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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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.

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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

RME
 

Unbal_DA-AD_2_x_USB_same_computer.png

 

Unbal_DA-AD_2_x_USB_same_computer_Intona.png

MARCH~audio
excellence in audio
www.marchaudio.com
 

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19 minutes ago, SoundAndMotion said:

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

First search delivered pages of hits which I am not going to search thru.  Second produced nothing. So I couldnt.  This is not a software issue.

MARCH~audio
excellence in audio
www.marchaudio.com
 

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9 minutes ago, SoundAndMotion said:

Sorry but just looked at that and see nothing relevant to PC activity (ie load) causing a problem.  Its a broken dac design, do you see the jitter issues over SPDIF?

 

We also have no idea how Amir set that test up, direct sound, wasapi etc etc.

 

MARCH~audio
excellence in audio
www.marchaudio.com
 

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7 minutes ago, SoundAndMotion said:

The OP shows it's software related. 

 

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

No it doesnt.  It shows he got different results with 2 different software which could be down to any number of reasons.  What Amir states:

 

Its brochure brags about "isolation" but the word "galvanic" is not there. This means that it is not isolated from the PC ground and that is feeding into the oscillator causing those correlated jitter spikes.

 

So Amir specifically state its a connection issue as I describe above.

MARCH~audio
excellence in audio
www.marchaudio.com
 

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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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14 minutes ago, SoundAndMotion said:

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.?)

I havent missed any point and it wasnt just opinion..  I looked at what Amir wrote and it confirmed what I said.  Amir said it was due to exactly the same reasons I did.

 

The fundamental problem is not PC activity.  A PC is "active" all the time.  The problem is specifically due to the lack of isolation in the USB connection.

 

ASIO from Roon.  Measured using REW via ASIO.  No I didnt use an isolator on the USB connection to the DAC.  Anything else you would like to know?  Happy to fill in  any blanks 😀

 

Also I will perform the same tests with a laptop tomorrow.

MARCH~audio
excellence in audio
www.marchaudio.com
 

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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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12 minutes ago, SoundAndMotion said:

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.

Its been explained. You are going round in circles.  Your semantics are irrelevant.  *ALL* pcs are noisy - period.  Thats just how they are.

 

The problem in that case is a non isolated USB connection.

MARCH~audio
excellence in audio
www.marchaudio.com
 

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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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18 minutes ago, SoundAndMotion said:

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

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... not 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.

 

Did I not say I was going to try another laptop tomorrow?  I also have an additional laptop and an additional PC to try.  I also have several DACs to try.  I never claimed this was anything more than an investigation, never claimed it was conclusive proof of a certain conclusion which you are making assumptions about.

MARCH~audio
excellence in audio
www.marchaudio.com
 

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15 minutes ago, idiot_savant said:

Well, this is going downhill fast...

 

There is an interesting question here : To what degree is "sensitivity" a good thing? 

On the one hand, you want a low noise floor and low distortion, good filtering etc in a DAC and an ADC to reveal as much as possible.

You also want this system to be as immune as possible from external influences ( mains, EMC, etc ).

 

And yet - I often see it stated that a product is "sensitive" because it reveals some difference in cables, processing or suchlike that can be simply explained by being marginal engineering. For example, I could transmit a high speed clock between two devices ( think a transport to a DAC via I2S ), but I accidentally fail to terminate it properly. The cable is now very important to the performance because of the mismatched ends, to the extent you can probably make it crackle by bending the cable. The DAC is now very "sensitive" to the cable, so you can "improve" it by cable tweaks. However, the *best* it can ever be is the *same" as the same design properly implemented ( i.e. properly terminated ).

 

Which would we prefer?

 

@March Audio has been fairly clear that he is demonstrating a system that is based on off the shelf components, with no tweakery, using components he regards as well engineered, and can see no differences. This *isn't* to say he won't ever find any differences as he refines his measurements, but so far there is nothing to see.

 

Comparing this system to one where the reviewer explictly says it is poorly engineered and not galvanically isolated and exposing a problem merely shows the problems you can get with marginal engineering. 

 

As boring as it may sound, good engineering will remove a lot of the "randomness" that people seem to enjoy tweaking around. I don't know about anybody else, but I'd rather listen to a system that sounds the same irrespective of the phase of the moon,

 

your friendly neighbourhood idiot

Well it will get moderated if people insist on going round in pointless circular arguments 😏

 

You make a very good point.  Its *not* a virtue for a DAC to be sensitive to what a PC is doing. Quite the opposite.  As is shown here its quite feasible to engineer a DAC that isnt sensitive.  Although this particular DAC is expensive, it doesnt have to be expensive to do so.

MARCH~audio
excellence in audio
www.marchaudio.com
 

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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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This is just a start.  No reason to refrain from taking it into controlled listening tests.

 

I read your posts.  It is you who is not listening.  I dont agree with you idiot_savant doesnt agree with you, we have said why.  Repeating yourself wont change that.

 

Yes repeating the tests with different PCs and DACs may not uncover anything untoward, but the whole point of investigating is to see if we can.  If nothing untoward is discovered then it still tells us useful information - that the problem isnt as wide spread as some seem to think.

 

I have no intention of suppressing views.  You have had your say.  What I wont allow however is a sensible discussion to turn into some of the stupid s**t fests we have seen recently with circular pointless arguments that dilute and distract from the point of the thread.

 

 

MARCH~audio
excellence in audio
www.marchaudio.com
 

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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.

 

image.thumb.png.0a48403bd3656fe0d936d6867b35595a.png

 

With PC loaded.

image.thumb.png.4db7e33ee0274d21d505a2cb8b7d1649.png

 

No significant difference.

 

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

 

MARCH~audio
excellence in audio
www.marchaudio.com
 

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