Solving computer noise over USB

Archived from groups: rec.audio.pro (More info?)

My wife got herself a Boss GS-10 and loves it. She especially loves using th
computer-based UI (in this case, on our PowerMac G5 dual 1GHz).

As soon as the USB cable is connected, though, we can hear an absolute racket
of computer noise coming though the mixer input from the GS-10. We've been
able to limit the problem by turning up the GS-10 input gain setting, turning
the GS-10 output to max, and turning down the mixer channel, but it's not a
total solution.

I did some research to try to see if there's a hub or some other device that
provides galvanic isolation for USB connections, but the only thing I could
find was an optical USB extender that retails for about $160.

Any other ideas?

Thanks,

Steve Jorgensen

Archived from groups: rec.audio.pro (More info?)

On Tue, 08 Feb 2005 02:55:31 GMT, Logan Shaw <lshaw-usenet@austin.rr.com>
wrote:

>Steve Jorgensen wrote:
>> As soon as the USB cable is connected, though, we can hear an absolute racket
>> of computer noise coming though the mixer input from the GS-10. We've been
>> able to limit the problem by turning up the GS-10 input gain setting, turning
>> the GS-10 output to max, and turning down the mixer channel, but it's not a
>> total solution.
>>
>> I did some research to try to see if there's a hub or some other device that
>> provides galvanic isolation for USB connections, but the only thing I could
>> find was an optical USB extender that retails for about $160.
>
>If you have a powered USB hub handy, have you tried plugging it in
>through there? It should isolate you from the +5V part of the USB
>for sure, and I believe the data parts of the signal are reconstructed
>by the hub (though I could be wrong), so it might isolate you from
>that as well. I'm not sure if it would isolate you from the ground,
>but it's possible since the USB data connection has a separate signal
>ground, so a powered hub *might* not need to connect to the regular
>ground.
>
>Anyway, it's not guaranteed to work, but it's one of those things
>that might work and probably costs nothing to try.
>
> - Logan

I had already tried that. I get identical noise with or without the hub. The
noise also really seems to be related to activity of the computer itself, not
to data through USB. In other words, it seems correlated with such things as
hard drive activity, etc., even if unrelated to audio work.

I was thinking some other model of USB hub might offer the isolation I need,
but I can't find any hubs that mention isolation in their specs, nor any
commentary by anyone that any USB hub does that. Perhaps, one does, and they
fail to make it known?

Archived from groups: rec.audio.pro (More info?)

Steve Jorgensen wrote:

> I did some research to try to see if there's a hub or some other device that
> provides galvanic isolation for USB connections, but the only thing I could
> find was an optical USB extender that retails for about $160.

I'd love to find the same thing. That USB cable makes a
superb little antenna and noise channel to bring everything
possible across from the system into the linear electronics
of the USB box if it has audio in it. Makes the "pin 1
problem" inconsequential by comparison. Optical isolation
of the serial data signals, complete isolation from system
ground and power which would be supplied supplied by the
isolator/hub. Yeah! No reason it need be expensive.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

Archived from groups: rec.audio.pro (More info?)

take a look at

http://www.fairchildsemi.com/an/AN/AN-5052.pdf

I'd sacrifice a USB cable making a test cable by cutting the data wires
on pins 2 and 3 as a test.

If you still get the noise when you use this test cable, then it is a
ground loop / power supply problem.

If that stops the noise, then it would be a data related issue.

Pins 2 and 3 carry the data.

Mark

Archived from groups: rec.audio.pro (More info?)

On Wed, 9 Feb 2005 09:43:09 -0500, Ty Ford <tyreeford@comcast.net> wrote:

>On Tue, 8 Feb 2005 01:55:39 -0500, Chris Canning wrote
>(in article <LnZNd.3033$mG6.1552@newsread1.news.pas.earthlink.net> ):
>
>> Steve Jorgensen wrote:
>>> My wife got herself a Boss GS-10 and loves it. She especially loves using
>>> th
>>> computer-based UI (in this case, on our PowerMac G5 dual 1GHz).
>>>
>>> As soon as the USB cable is connected, though, we can hear an absolute
>>> racket
>>> of computer noise coming though the mixer input from the GS-10. We've been
>>> able to limit the problem by turning up the GS-10 input gain setting,
>>> turning
>>> the GS-10 output to max, and turning down the mixer channel, but it's not a
>>> total solution.
>>>
>>> I did some research to try to see if there's a hub or some other device that
>>> provides galvanic isolation for USB connections, but the only thing I could
>>> find was an optical USB extender that retails for about $160.
>>>
>>> Any other ideas?
>>>
>>> Thanks,
>>>
>>> Steve Jorgensen
>>
>> It may be the G5 power supply that is suspect. Check out this link for
>> some others with similar problems.
>>
>> http://www.xlr8yourmac.com/G5/G5_noise_tips.html
>>
>> You may want to do some research on noise issues with G5's I've heard of
>> a similar thing happening with firewire as well as usb. I think the
>> current model of G5 has resolved the issue but not sure.
>>
>> Good Luck,
>>
>> Chris
>
>Apple said it was a poorly designed power supply. They also said using the
>CHUD developers tool to turn off processor cycling would fix the problem.
>
>After doing both, on my dual 2G G5, the unbalanced outputs of the Digi 002
>(over Firewire) still makes quite a racket.
>
>The dweeb at Apple said something like, "Sir we can't be responsible for
>knowing every single application the user might have in mind."
>
>My thought, " Hmmm 2 GHz, dual processor, perfect for word processing."
>
>My balanced 002 audio outputs are fine BTW.
>
>Regards,
>
>Ty Ford

I haven't worked with Apple as long on my problem, but I was complaining even
without the USB. The unbalanced connection between our Triton and out mixer
picks up enough computer racket to be an issue, and that's with no connection
to the Mac, after moving the Mac to one end of the chain of studio gear with
no audio wires running closer to it than about 3 feet, and with the keyboard
and its wires at least 6 feet away from it.

An Apple rep. has so far told me that there is a known problem that might be
affecting our system, and they'll swap the power supply if it has a specific
magic part number written on it. Only trouble is, taking the side off the
computer, it looks like the power supply is installed into the base of the
unit in such a way that you can't see it or what part number it has without
randomly trying various random dissection techniques until it is finally
revealed. I'm not really anxious to see how many pieces of Mac I can scatter
around.