USB, hubs, and signal quality

[Felig]

I have a nice little Edirol UA-1X sound device between my computer and stereo. USB in, optical digital out. It works perfectly unless I confuse it with too many USB hubs.

The basic configuration has two hubs, one near the stereo and one near the computer. They have about 30 feet of powered USB extension between them. The sound is full of static. If I bypass the computer hub and plug the long USB cable directly into the computer, the sound is fine. If I swap the computer hub for one of the same kind as the stereo hub, same static. If I leave the computer hub in place, and bypass the stereo hub, static, ie, it's not just having two hubs that does it.

If I use a short USB cable, and a long RCA cable to connect to the stereo, same symptoms.

To sum up, the sound sucks if there is a hub near the computer, regardless of whether there is a hub at the stereo, and regardless of the length of the USB cable. This is really annoying, as I want that hub more than the one near the stereo, since otheriwse I tie up half my USB ports with the Edirol device. The stereo hub is just in case I want some other USB device on that side of the room.

All connections are 2.0 as far as I know.

[Felig]

A friend suggsted electrical noise from the computer-side hub being, well, near the computer, especially since it is just 3-4 inches away from the monitor ... upon which I slapped my forehead, but it hasn't worked before, it's not likely it will rattle my brain any better this time

I added a nice long powered USB extension cable, got the hub about 10 feet away from the computer, no static! Moved it back towards the computer to see how far away it had to be ... no static even right next to the computer.

The extension cable I used is powered, and I reckon it must be better shielded because of that, or maybe it is just newer and has cleaner contacts ... at any rate, the Edirol gizmo now works fine with the hub near the computer.