Just a couple of tips..... not any A/B box works here. The way the SOB is designed, the two inputs are in series. When you plug guitar cords into both inputs to use an A/B, you unground IN1, which needs to be regrounded by the A/B box when you switch to IN2.... or else you can get noise, oscillations, etc.
Also, you need to keep the patch cords to the amp inputs short (2 feet is good), as the IN2 cord capacitively loads the circuit between V1A andV1B. The longer the cord, the higher the capacitance.... which kills your tone.... so keep them short.
It's not a great amp for switching inputs.... but a little care here can make it work.... You will have to work a little to balance the levels between IN1 and IN2 (since they are in series, and therefore interdependent). That being said, the SOB is in my opinion one of the best kept secrets in the history of amps..... I will never let mine go. Killer tone, loud, heavy, and more reliable than anything on the planet.
