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.
Convert?fit=crop&h=128&rotate=exif&w=128outlier
I would want it less than 10ft.

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".
According to Gordon Rankin (Wavelength Audio):
"2m for 24 bit dacs and 3m for 16bit dacs".

Is that for the analog cables, or for usb digital cables from a pc, or for coax or optical digital cables from a cd transport?

-- Al
That is a bit long. Any chance you could use optical?
If your DAC is 1st class and your system is very revealing, you will be satisfied with nothing less than the best short USB cable possible. In my experience, longer IC's are preferable. I have tried optical (allows a very long run,) and its OK, but no comparison to my current Ridge Street Audio 1m USB. Difference is night and day!
Thanks for the response guys. I'll play around with some variations. One upgrade I could pursue over time would be to get a new PC that's quiet, or maybe I can put some noise reduction felt or other absorbant material around my current PC and then position it together with my other gear.

Thanks,
John.
Al...

USB cable.
I build my own computers, and the quietest cases I am aware of are some of the Antec's, including the P180 and P182 models, and possibly (although I'm not certain) some of their more recently introduced models.

You might find this site of interest:

http://www.silentpcreview.com/

If you don't build your own computers, there are lots of custom builders out there, findable on the web, who I'm sure could make a very quiet computer, using these or comparable cases. You might also want to consider transferring the innards of your present computer into one of these cases, assuming that:

-- The computer is reasonably contemporary and performs satisfactorily.
-- The computer uses a standard ATX motherboard (Dell's, in particular, often use non-standard motherboards, and possibly power supplies as well, that will not fit into a standard case.
-- The computer's internal noisemakers that are not part of the case (cpu fan, hard drives, power supply, video card) are not unreasonably loud, or would be replaced with quieter counterparts.

Regards,
-- Al
Lokie -- Thanks. Interesting that he's recommending considerably shorter lengths than the usb2 spec specifies. Good to know.

Regards,
-- Al
The new flat WireWorld USB cable can handle lengths up to 7 meters. I have a 1.5m and 5m in my system and I can't hear a sonic difference between the two cable lengths like some other cable brands. BTW, the sound quality is superb compared to other cables (Kimber, Belkin Gold, Monster) costing the same price.