Hi geoffthemonk,

Welcome. You have some good questions -- as if there is any other kind... ha!

The signal your AVR sends to the subwoofer is tied to the volume knob, just as the rest of the channels are. All the level adjustment is done in the pre-amp stage before it is sent on to the amplifiers (internal or external). In that sense, the information the AVR sends to the sub is no different than the information it sends to its internal amps.

Does that clear it up?