Long runs - USB or RCA???

I'm considering an "external HD > laptop (PC - iTunes) > USB DAC" setup in my office. My audio rack is 15' away from my listening position where the laptop/exHD will be. My question is - do I position the DAC near the listening position and run 15' analog RCA cables to my integrated amp in the rack or do I site the DAC in the audio rack and run a 15' USB cable to the DAC? I know that with certain RCAs, I'll be susceptible to RFI; will a long-run USB cable potentially have the same problem? Any recommendations of either flavor cable to avoid the RFI? Thanks.
I've had excellent results with Monster Cable's USB cables, using a four meter run between my laptop and my USB dac on a very resolving high end system.
I would do the USB cable. Keep the ICs as short as possible. A basic USB cable should do the job just fine. If it makes you feel better, buy an expensive USB cable to keep any audiophile paranoia in check.
...sound like USB it is! Many thanks!
No, sorry guys! Long USB cables are no, no. Go for the long ICs.
15 feet of USB cable isn't what I would consider long. I couldn't hear any differences between 15 or 6 feet of USB cable. I know several audiophiles that use similar lengths..no problems to speak of.
I agree with Gmood1, here size does not really matter....and Ultrafitimes, how did you come to your findings? Long ICs are certainly OK, but cost a lot more then even a good long USB cable. I tried both, but could not really hear much of a difference, so I settled for the less costly version. I am using a Spoiler USB dac, which driven that way is in the same league sonically as the Zanden combo or the DCS stack, as I pointed out elsewhere in these pages..... and yes, even a humble Trends USB to digital converter will sound perfectly fine that way, driven through the Zanden DAC.
I don't have any direct experience with it but here is some information from the usb.org FAQ:

USB Cables, Connectors, and Networking with USB

Q1: How long of a cable can I use to connect my device?
A1: In practice, the USB specification limits the length of a cable between full speed devices to 5 meters (a little under 16 feet 5 inches). For a low speed device the limit is 3 meters (9 feet 10 inches).

Q2: Why can't I use a cable longer than 3 or 5m?
A2: USB's electrical design doesn't allow it. When USB was designed, a decision was made to handle the propagation of electromagnetic fields on USB data lines in a way that limited the maximum length of a USB cable to something in the range of 4m. This method has a number of advantages and, since USB is intended for a desktop environment, the range limitations were deemed acceptable. If you're familiar with transmission line theory and want more detail on this topic, take a look at the USB signals section of the developers FAQ.

Q3: How far away from a PC can I put a USB device?
A3: With the maximum of 5 hubs connected with 5m cables and a 5m cable going to your full speed device, this will give you 30m of cable (see section 7.1.19 for details). With a low speed device, you will be able to get a range up to 27m, depending on how long the device's cable is. With a straightforward cable route, you will probably be able to reach out 25m or so from the PC.

Q4: I need to put a USB device X distance from my PC. What do I do?
A4: If X is less than 25m or so (see previous question), buy a bunch of hubs and connect them serially with 5m cables. If you need to go farther than that, put another PC, or maybe a laptop, out where you need the device to be and network it with the first PC using something that's intended to be a long-range connection, such as Ethernet or RS-485. If you need to use nothing but USB, consider using USB based Ethernet adapters to hook the PCs together.
i use a 30 ft usb cable to my dac, it sounds ok to me, all i can say is it sounds better than apple AE toslink to DAC
USB 2.0 can be run up to 22 feet. USB 1.1 only about 12 feet. I would run the USB 2.0 cable to my DAC sitting on my rack near the amp. USB 2.0 is much cheaper than a 15 foot pair of interconnect and there should not be any degredation of sound.
Great reading...thanks for all the input!
Why not use a USB/SP DIF converter?Use a short USB cable to converter and then long digital RCA cable from converter to DAC.I currently do so in my office.
I use 10 metres (22 feet) of digital cable.Results are great.
USB signal is usually also converted to SP DIF inside the DAC.
My tech told me that long USB cable degrades the sound,but i never tried it.