Is it the old simple USB cable not having enough bandwidth?
No.
The Devialet
Expert 220 Pro, which is what I assume that you meant, is a stereo device. So if you are trying to play 192KHz 24bit stereo PCM audio, you need;
192,000 Cycles/Second x 24 bits/Cycle x 2 Channels = 9,216,000 bits/second, or 9.216 Mbps.
Any old USB 2.0 cable supports 480 Mbps. Yes, even old rubbish ones. Even if the cable has degraded, if it works it is still going to be supporting lots more than 10 Mbps. Well, unless there are an enormous number of retries happening, but that is easily tested with a simple file transfer over USB. Even an old USB 1.0 running at Full Speed supports 12 Mbps.
So;
Does Media Renderer (USB 2.0) ->old very simple USB cable->Devialet Expert 220 Pro work?
Does Media Renderer (USB 2.0) ->Transparent Audio Performance USB cable->Devialet Expert 220 Pro work?
If both the above work, then your
JCAT USB Isolator isn't allowing MC to see the capabilities of the
Devialet Expert 220 Pro, so MC is defaulting to 48 Kbps, or is able to at least see that the Devialet Expert 220 Pro is capable of that through the isolator. I would guess MC is defaulting to 48kHz.
The JCAT USB Isolator is a hardware product of JPLAY by the look. Hmmmm. If the simple tests above work, I think you probably need to take the issue up with JPLAY. Good luck.