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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
splaskin
170 posts
 
My PC is connected to a Wavelength Cosecant USB DAC by 60 feet of optical USB cable. The DAC feeds a Levinson 32 preamp. The optical USB cable is outstanding as I am unable to hear any noise. The Opticis is highly recommended. I also run the Opticis with a battery power supply (lithium). Additionl improvement is heard with the battery supply.
wkraft OP
8 posts
 
thanks for the lead. i will investigate. with regard to ckrody's comment that the u24 gets its power from the usb, is noise less of an issue with self-powered usb dacs, and do many other usb dacs have the sample rate conversion ability to operate without the u24?
splaskin
170 posts
 
Ckorody,

If you want to experience fabulous digital playback, consider the Wavelength Cosecant. I am able to select and control my musical selections with NetRemote-J. River Media software with a pocket PC using a Wireless LAN. A dedicated power supply would be superior for a USB DAC.

Steve
ckorody
643 posts
 
Yep -saving up for the next great thing... Steve and Gordon both have some nice things to consider =)

For Wkraft - please forgive me if you know this....

The Waveterminal is just a device for converting USB to SPDIF/Toslink. Actually it has a DAC built in too, but I have never seen anyone comment about using one. It was developed and marketed to the semi-pro audio recording market

As a general point of info, USB devices come in two flavors - those that require a dedicated power supply (because they need more juice), and those that can draw their power from the USB cable. In fact the Opticis needs a power supply and what Steve has done is create a DC one instead of the AC wall wart. The U24 is an example of a device that does not need its own power source. But effectively that leaves it connected to the computer...

I would assume that any USB DAC (certainly all that I am aware of besides the Waveterminal) require a dedicated power source, though some (like the RedWine units) are battery powered since the DACs tend to operate at 5v.
wkraft OP
8 posts
 
to elaborate- the waveterminal running into the coax digital input of my panasonic sa-xr55 (i know many will turn up their noses at this class d based unit) results in dead quiet speaker and headphone output. this prompts me to wonder what in the receiver prevents the noise transmission. i see that most audiophiles are not using the u24 dac function, and i am thinking ahead- would implementing certain kinds of dac obviate the need to uncouple the u24 from the dac.
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