2. pc-audio
  3. 1150170453

any words of wisdom for usb noise problems?

i thought usb connections would be trouble-free after placing waveterminal u24 between my desktop pc and the dac in my panasonic reciever (office system). itunes runs dead quiet there. i am trying to implement a pc feed into my levinson preamp in main system. when the usb cable makes contact between my laptop pc and the u24 running into the preamp i get substantial noise, which is substantially worse when a usb hard drive is also attached.i googled "usb noise" and saw references to some midi users' and photo printer issues and some filter products (argh!- hope to avoid this step). also mention of computer screens as possible culprits any suggestions or similar experiences?
wkraft

Showing 3 responses by vfoostdijka929

vfoostdijka929
3 posts
 
Or, instead of a DI-box, an inexpensive ground loop isolator:-)
vfoostdijka929
3 posts
 
This is clearly a design fault of the U24. They should have put a circuit inside to clean the power via usb and/or add the possibility to connect the U24 to an dedicated external power supply.

I tried an external USB-hub with it's own external power supply. Unfortunately the U24 isn't recognized by the computer when connected via the hub but maybe this is just a matter of reinstalling the U24 drivers.

I am thinking now of modificating the U24 to make it work with an external power supply. The easiest way is probably to cut the USB cable in two and connect pins 1 and 4 of the part which leads to the U24 to an external power supply.
vfoostdijka929
3 posts
 
I found the solution for the noise problem and it is amazingly simple and totally free, at least in my case, but I think also for a lot of other users of external soundcards in general.

The problem was not the quality of the power supply.
The digital noise was created by a ground loop between my laptop, the U24 and my audiomixer. All noises disappeared instantly by plugging the laptop's power adapter in an unearthed AC outlet. Bye bye ground loop, bye bye noise!

If you don't want to leave your laptop (or computer) without an earth connection, the other solution is to add a line level DI-box in your analog audio in/out lines.

Best regards,

Vincent
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