Hi,
In the past year I've had both of my 7B SSTs in for repair, and now they have different volumes ( gains ). I swapped the amps around, so I'm sure that it's not a cabling or preamp problem. As a workaround I'm running one amp at 1V gain and the other at 2V and now they are both producing roughly the same volume. Hardly an ideal solution though. I guess I have to send my amps back in. Right?