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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
ckorody
643 posts
 
Not a design fault - more likely a design decision, and by modern standards by now an old design. The U24 was built as a semi-pro recording studio product, not as an audiophile product. Recording studios are filled with all sorts of devices using less then optimum electronics.

BTW the hub may not be able to power it.

Using the Opticis fiber optic USB may give you that last degree of quiet you are looking for.
audioengr
3,282 posts
 
There are two fundamental problems with the Waveterminal:

1) it uses the power from the USB cable
2) it does not have any isolation to break the ground from the computer to the audio system

These things are difficult to get around without modding the thing. The Opticis will help with (2), but not (1).

steve N.
Empirical Audio
Manufacturer
slothman
311 posts
 
Steve,

Problem "1" pontentially solved utilizing a battery powered USB hub
For a $17 gamble I'm game to investigate a possible improvement to an already excellent device - love my U24!
slothman
311 posts
 
My prevoius post may have been premature... here is an interesting product I stumbled upon as well. It's basically a 5V battery pack built in the middle of USB cable. I can't seem to find the power requirements for the U24 in the manual but this product looks like it may work with the Waveterminal. I may bite and report back with my results. The battery powered hub that I came across but may not be powerful enough.
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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