Long USB Cable OK?


I just purchased an Ultra Fi iRoc DAC (haven't received it yet), and intend to use it with a media PC that has iTunes (I've all my CDs on the HD on Apple Lossless format).

Question I have is whether it is ok to use a long USB cable from my PC to the DAC? Currently my PC is about 18 feet from my Audio System. I can then connect the DAC to my Preamp with a very nice analog pair of ICs (1M pair of Acoustic Zen Absolute - I think retail on those was about $2.5k). Also, can I use a regular length USB cable and an extender (I have an extender already, so am just wondering if I can use that too, without any sonic impairment)?

Alternatively, I have a very long length of cheap analog ICs I can use (and keep the DAC close to the PC with a short USB cable).

I keep the PC out of the way because its noisy and prefer not to have it alongside the audio system and speakers.

Any advice welcome. Thanks!
John.
128x128outlier
USB2.0 is specified for a maximum cable length of 5 meters, or about 16.4 feet. You might get away with 18 feet, if you obtained extension cables that add up to that distance. If not, you could put a powered usb hub somewhere in the middle of the run, and that should work fine.

I would not put the dac near the pc, and run the analog signals through a long cable. My main concern would be that digital noise generated by the pc would couple onto the analog signals. And of course there is also the possibility that the long cable itself could degrade the analog signals, for instance by the cable's capacitance causing a treble rolloff if the dac's output impedance is not low enough to prevent that.

Regards,
-- Al
According to my experience I agree completely with Al. After much experimentation I use 4m of a Monster USB cable without any sonic detriment.
Although I can hear a difference in usb cabling, on my second system I use an optical 10 meter usb cable. I prefer it over wifi. On my main rig I am using a 2m Kimber Kable and like it very much...
According to Gordon Rankin (Wavelength Audio):

"2m for 24 bit dacs and 3m for 16bit dacs".