I bought a used Lehle Dual SGoS from a TGP seller for $250 and the previous owner was kind enough to build me 2 custom MIDI cables for it. I run it with a custom MIDI cable and use it to switch between 3 different combo amps with a Lehle P-Split to isolate the 3rd combo amp. The Dual SGoS is more expensive, but the ground lift, phase reverse, great sound quality, & MIDI programmability makes it top notch on the other A/B boxes on the market.
Guitar George