sound problems with speakers going thru USB hub

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liz

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Feb 14, 2011, 8:22:22 AM2/14/11
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My USB speakers sound crackly when I plug them in via my USB hub. When the
speakers are plugged in direct to a PC USB port they sound alright.

My USB hub is a cheap device. Would a higher quality USB hub make a
difference or is the bad sound inherent in the way any multiway USB hub
works?

Grinder

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Feb 14, 2011, 11:49:38 AM2/14/11
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Is your hub powered through a USB port as well, or does it have it's own
wall wart? If it's the former, that could be your problem.

John McGaw

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Feb 14, 2011, 7:19:19 PM2/14/11
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...and are other USB devices connected to the computer through the hub? If
so, they could be using up bandwidth that the speakers need to operate
properly since there is only so much of it to go around. If you have other
devices on the hub you could disconnect them, possibly one-by-one, to see
what effect it might have. You might be lucky and find that there is just
one which is not playing nice and sharing and then move that one to the
computer.

liz

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Feb 15, 2011, 3:36:23 PM2/15/11
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The speakers are the only device on the hub so there's no others to
eliminate.

The problem is a funny sort of crackle.... it sounds like the recording is
an old scratched vinyl LP.

liz

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Feb 15, 2011, 3:38:10 PM2/15/11
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The USB hub is powered from the USB port it is plugged in to. Doesn't sound
like pwer supply distortion.... it's a sorta crackle as if the recording is
from an scratched old vinyl LP.

Paul

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Feb 15, 2011, 8:50:30 PM2/15/11
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Crackling used to be caused, years ago, by data underruns on the sound
card. That means, the sound device asked for data, and the card wasn't
able to do DMA in time, to keep the buffer full.

When you have issues like this, you can learn a lot, by looking at the waveform
of the signal. Now, with USB speakers, that's going to be difficult. If the
USB speaker has a headphone jack, you might loop the headphone jack back to
a sound input port on another computer. Then record the signal from the
sound system. If the crackling was random spikes, it might be an analog
power issue. If instead, you see "flat spots" on the waveform, that
can be data delivery issues.

(One of the issues I've been working on, on and off, for a few months.
There is a "skip" in the data here, which causes crackling.)

http://img813.imageshack.us/img813/1761/softwarebreaksasinewave.gif

I'm not familiar with USB having such issues. I would think, even if the
USB port was running in USB 1.1 mode, it would work. 2*16*44100 = 1.4 megabits/sec
should be handled on a 12 megabit/sec USB interface. You'd have to drop
down to "Low Speed" mode (something used with unshielded USB cables and
keyboard type devices), to be getting close to a limit like that. It is
even possible, the interface for a USB sound device, is run in isochronous
mode, to better guarantee the bandwidth needed.

http://en.wikipedia.org/wiki/Usb

You can use a tool like UVCView, to examine the technical details of the
USB device. But that is hardly likely to lead to a solution. It might
be faster to just verify you're using a USB 2.0 hub (which reclocks data),
than to waste time trying to get that utility. Maybe your hub is an
older USB 1.1 device of some sort.

*******

This is one way to get UVCView. From "Joe Morris"...

UVCView is shipped with the Windows Driver Kit.

http://msdn.microsoft.com/en-us/library/ff554257(v=VS.85).aspx?ppud=4

The download you end up with is:

GRMWDK_EN_7600_1.ISO 649,877,504 bytes

Using 7ZIP, navigate to "WDK" and find

avstreamtools_x86fre_cab001.cab

and clicked on the cab, do an "Open Inside", then select

_UVCview.exe_00006

then extract. Then rename the extracted file to

UVCView2.exe 133,632 bytes MD5SUM=213f6e89cc4ab4e7e9e3e2ad394b83cb

Using that method, avoids having to install a lot of cruft
you don't need. You still have to figure out, how to read the
config data on the right hand pane, which isn't exactly easy.

This is a picture of what the UVCView info looks similar to.

http://www.die.de/blog/content/binary/usbview.png

Some information on the parameters seen in UVCView.

http://www.beyondlogic.org/usbnutshell/usb5.htm

Good luck,
Paul

Nobody > (Revisited)

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Feb 21, 2011, 1:38:33 AM2/21/11
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Still, even "unloaded" plain-jane USB hubs can add problems to anything
plugged into them.

If you don't have easy access to your "on the pooter" USB ports (as they
are all on the back in the motherboard ports area), get a short USB
Extension Cable (Type A Male - Type A Female).

--
The black flies were coming.
(Alastair Mayer in "Small Penalties")

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