USB audio is pretty much a real-time process; the computer
MUST deliver packets every so many milliseconds and, if a packet goes missing (usually because the computer "gets busy" for a split second), then you often get a stutter. The most obvious and common cause of this is that some other program simply
DEMANDS the computer's attention for a split second.... (which would be "a high priority interrupt" in computer terms). The way to avoid this is to avoid having other programs running that do it. AntiVirus programs are prime offenders, as are things that do automatic updates without telling you... certain WiFi and graphic drivers also do it, so always make sure those are up to date.
Also, just in general, avoid running other programs on computers that you use for music. Some computers can play HD music while running ten other programs and doing a virus scan; others seem to glitch if you try to do
ANYTHING else while the music is playing. If you think this is happening, first try playing your music with nothing else running. Then, if the problem goes away, you can try and figure out which things you can get away with. You will also find that some computers have trouble with multiple USB devices running at once. (They may do fine with a USB DAC when playing music from their own hard drive, but always have problems when you play music from a USB drive.) So, if you're having trouble, always try putting your music on a local HD and see if that helps. If your computer has many USB ports, they may be connected to different internal hubs. If so, then you may find that you can only play music on a USB DAC from a USB drive if they're NOT plugged into the same internal hub; so try plugging one into a front-panel port and the other into a rear panel port.
Some USB sticks may simply be too slow to work well for music (and some USB drives go to sleep, and you may get a stutter every time they doze off and wake up again).
Finally, some really old and underpowered computers simply have trouble playing music - but that sort of depends on what player you're using and lots of other factors. (A dual core machine with 1 gB of RAM should do fine with Windows XP or Windows 7 - as long as you don't ask it to do other stuff at the same time. I've seen an old 700 mHz Pentium, with 256mB of RAM, running Windows XP, do just fine - so it really depends.)
Many programs also have options specifically designed to help avoid dropouts. For example, if you're using Foobar2000 and WASAPI mode, you'll have a setting for "buffer length"; and adjusting that can help a lot. There isn't a "correct" setting, and larger or smaller buffers may work best on a given machine, so simply try different settings and pick the one that works best. (Don't assume that bigger is better; picking too
LARGE a value can cause dropouts.)
iTunes would NOT be on the top of my list for playing music on a PC anyway...
; I would much more recommend Foobar2000 (if you like simple) and jRiver Media Center (if you like big busy programs like iTunes).
Finally, although they should work just fine with our DACs, Schiit's C-Media drivers are basically identical to ours, so I wouldn't expect them to make a significant difference.
(It would be more likely that uninstalling and reinstalling the drivers changed a setting somewhere.)
Also, until the web gang gets the drivers up on the DC-1 page...... the drivers for the XDA-2 and the DC-1 are the same, so you can just download them from the XDA-2 product page.
NOTE:
The the newer "unified" drivers support everything up to and including Windows 8, but
DON'T support WASAPI Event; they only do WASAPI Push (so you'll have to "Disable Event mode" if you pick WASAPI in jRiver Media Center).
The older drivers support both WASAPI Push and WASAPI Event, but don't support Windows 8.
(I don't know why C-Media withdrew support for WASAPI Event in the newer drivers; I've also never heard any difference between the two WASAPI modes anyway.)
Didn't get the chance to try another input, but reinstalling the driver or installing Schiit's one didn't fixed the issue.
I can also try foobar, to check if it's an usb issue, or itunes...
; I would much more recommend Foobar2000 (if you like simple) and jRiver Media Center (if you like big busy programs like iTunes).