Wilfred:
I have to respectfully disagree with Brother Paul TBO. The SF-2 can easily be used with two amps. In fact, I am sitting here with the manual schematics in front of me. There are two ways:
1. USING THE SF-2 AS A PRE-AMP: Plug your instrument into the front of the SF-2. Set it for stereo in back. Run CH A OUT to one amp, and CH B OUT to the second amp. (The pre-amp gain on the SF-2 can be set by an internal jumper to 0db, 10db, or 20db. Coming from the factory it is set at 10db gain).
2. USING ANOTHER PRE-AMP: Plug your instrument into your pre-amp. Run the output of the pre-amp into the back panel of the SF-2 at the CH A IN jack. THe SF-2 should also be set on stereo. Just as above, run CH A OUT and CH B OUT to the two amps.
I don't know how this will work with bass, but when running a guitar with two amps, it helps to fatten up the sound by putting a very short delay on one of the amps.
Good luck,
Bill, tgo