I've just purchased a G75 Relay, and although the connection is fine on a clear channel (no dropouts, I had been concerned after all I'd read), I am having terrible noise problems.
The unit shipped with a USB PSU (Got to hate that.. Micro USB connectors in a live environment??) and initially I had difficulty getting it to power up - it would display a red LED and flickered the screen once. A bit of cable wiggling and it started up and continued to work fine. That first night I had no noise issues but each time I was jamming with it, on startup I would have to wiggle the USB power cable.
I then purchased a 9v PSU (1A, low-noise allegedly) and that cured the startup issue. Comes on immediately every time. However, in practice I noticed a lot of noise on my rig. I thought it might be the rehearsal room but when I gigged at the weekend I had to go back to the cable as the unit was making so much noise.
So, I guess my question is, which is better - USB or 9v power? And are these units particularly susceptible to a noisy psu? It sounds like a mains hum to me. I don't think it can be digital interference. Plugging the bass (Ibanez SR2605) directly into the cable going out of the transmitter removes all the noise. So it's not a cable problem.
Any suggestions gratefully received.