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-   -   Better converting usb or spdif? (https://www.diyaudio.com/forums/pc-based/216356-converting-usb-spdif.html)

Dirk95100 18th July 2012 07:47 AM

This is what I got when googling for common mode noise:
common mode noise - Google zoeken

;)

phofman 18th July 2012 09:01 AM

Quote:

Originally Posted by wwenze (https://www.diyaudio.com/forums/pc-based/216356-converting-usb-spdif-post3095979.html#post3095979)
About this I need assistance, I failed to find a way to change the latency setting for USB DACs running on Windows' standard drivers. No ASIO driver either.

I have never seen a way to change low-level USB audio latency for windows. Most likely you can change size of audio buffer in the player but that will affect only the process of the player. The USB controller reads via DMA USB packets prepared in advance by USB audio + USB core drivers. I do not think you can change how much the driver is ahead of the USB controller (which is what has been suggested - to give the OS more headroom/time before it must provide new samples). Unlike in linux - for specific details http://www.diyaudio.com/forums/pc-ba...ml#post1719044

wwenze 18th July 2012 09:38 AM

Quote:

Originally Posted by abraxalito (https://www.diyaudio.com/forums/pc-based/216356-converting-usb-spdif-post3096226.html#post3096226)
Not to mention less CPU work to do means less power drawn, less power means lower noise = better sound.

So my PC's soundcard is less noisy when the CPU is under load? - An investigation on computer activity and audio noise

abraxalito 18th July 2012 09:43 AM

So in those FFT plots you're doing a loopback test on a single soundcard? If so then that won't take account of CM noise from the SMPSU which I reckon is the biggest cause of sound degradation to an external DAC.

wwenze 18th July 2012 09:45 AM

Realtek out -> Xonar DX in

abraxalito 18th July 2012 09:58 AM

Ah yes, so you're seeing the difference in potential in the local grounds there. The buck switcher for the CPU is probably the source of those noise bumps around 2k - 4k.

<edit> those two bulges look most worrisome because the CPU switcher's frequency isn't anywhere near 2-4k. So to me that looks like folded down noise that originally was much higher freq and got aliased somewhere at the ADC.

erin 18th July 2012 01:57 PM

I think there will be a difference between a pc used with a soundcard as a source, and a pc with spdif, or usb audio output used as a transport.

Also you mentioned that you could not replicate your results with a desktop pc, and this suggests to me that your results are applicable only to your laptop, though could apply to other laptops.

I think you should keep an open mind with regard to reducing processes at least on desktop pc's - there are too many respected people who have heard the improvement to ignore this suggestion.

qusp 18th July 2012 03:36 PM

Quote:

Originally Posted by Dirk95100 (https://www.diyaudio.com/forums/pc-based/216356-converting-usb-spdif-post3096240.html#post3096240)
The quality of a digital system is only dependant on the quality of the converters nothing else.

haha, right, have you thought about where we are and what we are talking about in this thread? thats a ridiculous position to take when we are talking about 2-4khz hash and stuttering in the audio playback. you know of a dac that causes such artifacts?


Quote:

Originally Posted by phofman (https://www.diyaudio.com/forums/pc-based/216356-converting-usb-spdif-post3096341.html#post3096341)
I have never seen a way to change low-level USB audio latency for windows. Most likely you can change size of audio buffer in the player but that will affect only the process of the player. The USB controller reads via DMA USB packets prepared in advance by USB audio + USB core drivers. I do not think you can change how much the driver is ahead of the USB controller (which is what has been suggested - to give the OS more headroom/time before it must provide new samples). Unlike in linux - for specific details http://www.diyaudio.com/forums/pc-ba...ml#post1719044

didnt know the audio hardware of the OP, but one thing is for sure, this isnt a problem with the dac; its an issue of process priorities. his i3, properly setup could play 384khz without breaking a sweat. there is a software problem, so I mentioned a few sources of memory glitches.

there are all manner of pro and prosumer USB interfaces that will allow adjusting latency/buffer size, I did not specifically mention USB data latency, i'm talking about the player or the hardware driver. it was actually a bit of a textual slip, I was meaning buffer size, I inserted latency as a slip due to in this case being the dominant factor, if you adjust the buffer size this number will dominate latency

marce 18th July 2012 07:45 PM

Dont forget simultaneous switching noise when discussing the noise in PC's, look at the noise from a mians powered system and a battery powered system (with its main supply being linear) and there is still lots of noise present created by the circuitry switching, you can get instantaneous current draw in the hundreds of amps when cpu's fpga's etc switch. This is one if not the main source of digital noise, and why digital is used cos its imune to this noise as long as its levels are controlled by decoupling (the main source of decoupling for PCBs etc is the on chip capacitance, then the power ground planar capacitance, then the decoupling caps. These supply the required charge in the order listed, being filled up like a bucket brigade by the next slowest link in the chain, the main power supply being last. Its not all SMPS's.
http://www.ee.ryerson.ca/~fyuan/ssn.pdf


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