I am using the 272 amp to power my left and right speakers...and recently installed outdoor speakers that I'd like to use when I select "B" on the A/B switch on the 762. Here's the problem: when I connected the outdoor speakers to the corresponding binding posts for "B" speakers on the receiver, I didn't get sound outdoors (though the receiver's panel indicated that the B's were on -- I tried just about every combination). I then removed the speaker wires from the back of the receiver and connected them to the posts designated for the B speakers on the 272. In this scenario I cannot turn the B's off -- when the main speakers are on, so too are the speakers outdoors.
Naturally, I'd like to be able to use the A/B switch to use any combination of speakers: A's without B's, B's without A's, both simultaneously.
In an A-B set up you are only using one amp for both sets of speakers. When you connect your pre-amp to the amp using one set of interconnects you have connections for one pair of speakers. Unless your amp has an A-B switch thats the only way it will work.