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Investigation Into Effects Of PC load On DAC Analogue Output


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1 hour ago, March Audio said:

Your hearing works spatially by assessing timing, amplitude and frequency response.  Responses that are modified by your head, torso and ear shape.

This is only an extremely small subset of the whole process (not to mention your vague use of "timing" and "amplitude", without mentioning what particular properties/structure of that is relating to spatial perception). You can't insert your random assertions everywhere and get away with it. That is neither objectivity nor science.

 

1 hour ago, March Audio said:

OK Manuel, would you like to tell us all about your knowledge of the subject?  Tell us how it works?

Not falling for this bait as it'll take the thread off topic.

 

1 hour ago, March Audio said:

How do you think that things like Q sound Work?  They manipulate these factors.

I have no reason to predict how a particular tool goes about doing its job, or how accurate it is on this aspect, since the whole domain is constantly evolving and better solutions from better models are often released.

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1 hour ago, manueljenkin said:

This is only an extremely small subset of the whole process (not to mention your vague use of "timing" and "amplitude", without mentioning what particular properties/structure of that is relating to spatial perception). You can't insert your random assertions everywhere and get away with it. That is neither objectivity nor science.

 

Not falling for this bait as it'll take the thread off topic.

 

I have no reason to predict how a particular tool goes about doing its job, or how accurate it is on this aspect, since the whole domain is constantly evolving and better solutions from better models are often released.

Really?  Then please go ahead and explain what these other major factors are.

 

There is nothing random or vague about what I have said.  Its quite the contrary, it is yourself that is coming up with random hand waving assertions.

MARCH~audio
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7 hours ago, March Audio said:

Must to add, for soundstage to change the frequency response, phase (timing), or amplitude would need to change.  The tests look at all of those things.

Many a subjective experiment concentrated on reducing common mode noise has made improvements in soundstage. The worst scenario is a laptop connected directly to a DAC via USB (with a printer cable). Common mode noise can ruin an image very easily.

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7 minutes ago, opus101 said:

 

One of the major factors you omitted was depth perception. Could that be because you dismiss soundstage depth as 'an artificial construct' ? In truth its no more artificial than any other audible illusion portrayed by a stereo system.

Why do think its ommitted.  Why do you think 'spatial perception" doesnt cover it?

MARCH~audio
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Are you saying 'spatial perception' does cover it? To me 'spatial perception' would most certainly include L/R imaging - that's perceived by a completely different method than depth. So you want to lump them together?

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7 minutes ago, opus101 said:

Are you saying 'spatial perception' does cover it? To me 'spatial perception' would most certainly include L/R imaging - that's perceived by a completely different method than depth. So you want to lump them together?

Eh? Since when has spatial perception only been limited to 2 dimensions? 

MARCH~audio
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15 hours ago, One and a half said:

The images of the waveforms don't tell the whole story. A PC is a common mode generator par excellence. There are so many smps and pwm controllers on the motherboard, that anything connected will receive a fair dose of noise, this includes USB, AES3 cables.

The images don't show how the soundstage is set, how wide or narrow the instruments are placed in music. From my humble experiments with the DX ISO filters on ethernet transmissions, there's more up the upper end of the conducted EMC spectrum that causes soundstage errors in DACs. Yes these are heard and are subjective. By removal of upper audio band noise does the audio soundstage improve.

 

Here's a paper on common mode noise on AES3 transmissions for interest.

 

 

AES2003.pdf 834.39 kB · 4 downloads

 

Moreover non-linearities are caused by system responses to complex inputs that are not the mere sum of sinewave sweeps. 

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On 6/14/2021 at 6:53 PM, idiot_savant said:

Erm,

 

sorry to be pedantic, but this thread is about PC load? Can that change common mode noise? If so, surely we can measure it? As for ringing, it’s not showing up on the DAC output? The thread is about common conceptions  - if the DAC used in the test is “too good”, can someone suggest one more likely to show differences?

 

 

 

 

 

your friendly neighbourhood idiot 

 

PC load most certainly can and has been shown to affect common mode noise. There is a measurement of this in one of my classic textbooks on high speed digital design/RF mitigation etc. I can't recall which off hand. I'm going to guess Ott but if not then Johnson.

 

In my experience the Pre Box Digital S2 which is an outstanding though very cost effective DAC is more input sensitive than the iFi iMicro DSD to keep this discussion to commonly available and relatively inexpensive DACs that I like the sound of.

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8 hours ago, jabbr said:

 

Moreover non-linearities are caused by system responses to complex inputs that are not the mere sum of sinewave sweeps. 

Again please read the thread.  You missed the complex multitude test which also showed no differences when the PC was loaded.

MARCH~audio
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www.marchaudio.com
 

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8 hours ago, jabbr said:

PC load most certainly can and has been shown to affect common mode noise. There is a measurement of this in one of my classic textbooks on high speed digital design/RF mitigation etc. I can't recall which off hand. I'm going to guess Ott but if not then Johnson.

 

In my experience the Pre Box Digital S2 which is an outstanding though very cost effective DAC is more input sensitive than the iFi iMicro DSD to keep this discussion to commonly available and relatively inexpensive DACs that I like the sound of.

Again please show the evidence.

 

How did you measure the effect in the dac output?

MARCH~audio
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2 hours ago, semente said:

Is this of any relevance?

 

Perception of mid frequency and high frequency intermodulation distortion in loudspeakers, and its relationship to high-definition audio.

 

 

 

Griesinger_IMD-perception.ppt 1.16 MB · 3 downloads

Not really.  Without discussing the content of the paper, uktrasonic intermodulation products need to appear in band, ie below 20kHz to be audible.  So far We have seen nothing even vaguely audible change between the PC unloaded and pc loaded states.

MARCH~audio
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www.marchaudio.com
 

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So back to some more measurements of the Gustard X16, this time from the single ended RCA output.

 

This is with the PC unloaded.  This time, compared to the balanced XLR output we see spuria at 50Hz and harmonics at 100Hz, 150Hz etc.  Several reasons behind this; using the RCA output has reduced the CMR of the ADC input, so those mains spuria will have less rejection.  Also, noise currents that in XLR connections will be (mostly) harmlessly carried in the separate shield wire,  can end up in the RCA signal low (shield).  They can range from classic ground loops to leakage currents from SMPS to general noise from the PC.

 

In this case we can see that the spuria are still only at extremely low and inaudible levels.

 

image.thumb.png.f56377bed29f8259e9057f6cfcab743a.png

 

 

PC Loaded - no significant difference.

 

image.thumb.png.27311dd01caaa81682a70a2bd83f9f7e.png

 

 

Jitter - PC unloaded.  Finally we have something interesting to look at.  We see the same 50Hz sidebands as with the XLR connection but also some addtiional spuria at 11kHz and 13kHz.

 

image.thumb.png.1e9307e417b1051dd935769aa4fcc273.png

 

lets widen the view. Its spread throughout the ranhge.  Note higher spikes at 8kHz and 16 kHz which coincide with USB packet noise.

 

image.thumb.png.ccdf9922f92a54dc5e16876172cbe130.png

 

With PC loaded - No significant difference

 

image.thumb.png.b10772350e9d920b1a368538cec3debd.png

 

So the RCA connection is showing some very minor issues - we are down below -150dB.

 

Lets put a galvanic isolator in the Gustard USB connection.  The major spuria have gone.  However we still see some 50Hz contamination.

 

image.thumb.png.fb74d559c2e8ee85a9694c4b4546d95d.png

 

 

Next I will look at another RCA single ended output DAC.

MARCH~audio
excellence in audio
www.marchaudio.com
 

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