I had a HeadRoom BitHead that has served me wonderfully, but I figured it was probably about time to try to clean up some of the noise. So, I ordered a little choke from DigiKey to stick on the USB rail; new op-amps to upgrade it to "Total BitHead" specification; and decided to put some aluminum foil tape on it to try to keep out some of the RF hash from my phone. All upgrades were successful! There is now less noise when on USB power; somewhat less noise from my phone; and my brain has convinced itself that the new $20 worth of op-amps sound better than the old ones.