Crazy problem: USB port provides bad sound, but only at low CPU usage, Was: CrazyProblem:BadSound@lowCPU-usage (Please use your space bar.) Options

[reselty]

Hello
USB port provides poor sound quality

It’s a Windows XP or Hardware not a DJ-Soft Problem.
Only I do not know, where I could ask such a question otherwise.

Problem occurs when sound output via USB (via Jack OK).
- Via ext USB Sound Card
- Via USB Headphone / Mic earphones (which have a well-integrated sound card)

No Problem when:
+ powered USB hub between PC and sound card "sound OK" ( "bad sound" without power )
+ The REALLY WEIRD: if I increase CPU usage, e.g. if I move a window in Windows continuously the output is OK

Attachment: 2 WAV sound files:
http://dl.dropbox.com/u/39224041/USB-out-WAV%27s.zip
I'm alternating every 10 seconds during playback,
- move a window in a circle permanently CPU Usage 60..64% >> Sound ok
- Then without window moving CPU Usage 2...7% >> sound bad
Each WAV starting with window moving(so: 10s good, 10s bad, and so on (etc))

Could it be due to the USB power? (Not yet measured)
I've read that some USB devices could damage PC.
"This could, in extreme cases damage the USB port on the host or upset the energy management of the computer, which can lead to unstable behavior."
Possible? While yes: enough to measure only via Soft-PC-Diagn.Tool e.g. SpeedFan? Or do I have to measure with a MultiMeter?

Could it be speed of USB?
My PC has USB2.0, however I have not found out about whether "Hi-Speed" or "Full Speed"

What ever could it be???

Am glad to rest every tip, even to the other proposals in which forum should be posted!
Thank you
Reselty

[slks]

If you could tell us how the audio sounded "bad" we could give a better answer.

My gut reaction to this is that it should not be possible - USB only transfers digital data, which means that the data either gets to the external sound card, or it doesn't. There should be no degradation in quality, at least until the signal reaches the end of its digital path in the external sound card, and gets converted to analog. But I'm willing to consider that errors interrupting the digital data transfer could cause audible problems. It could be something like power saving schemes trying to shut off the USB ports, like the previous poster suggested. IIRC, data flow control over USB is also done through the CPU, so putting the CPU under heavy load could cause interruptions to the data flow. (However, data interruptions while the CPU is under less loads, I could not understand.) I imagine such interruptions would sound like skips in the audio, possibly only milliseconds in duration, which would make them sound more like small pops, similar to dust in the grooves of a vinyl record.

Perhaps someone with more computer engineering background, or knowledge on how these external sound cards work (do they have their own buffer to fight data flow interruptions? how large is this buffer? etc.) could fill in the gaps of my knowledge. A more detailed description from you as to what exactly happens to the sound when it gets "bad" would also help in diagnosis.

edit: Wow, I glazed over your .wav samples somehow. The clips sound distorted to me from the beginning to end, and opening them up in an audio editor confirms that they peak at 0 dB throughout. That is to say, they've been recorded way too loud. Try recording them again with the volume turned way down, so that we can hear what it going on, not just clipping distortion

This post has been edited by slks: Jan 20 2012, 14:55

[reselty]

Answer 4 slks

Thanks a lot about your thoughts.
USB only transfers digital data - as I thought..
errors interrupting the digital data transfer - didn't thought about that, but why not! perhaps like zima explained
someone with more computer engineering background - would be nice..
about the uploaded sound - hope you'll listen to the new uploaded files, for me it is not easy to explain in words the craziness. But today I first tried with the USB-Headset and it sounded not anymore like sound (would had the possibility to record it), than I tried the ext.soundcard WITHOUT power (forgotten) and there was no problem.