An amplifier basically is a power supply section connected to one or more channels of output transistors, which serve as valves to add the required amount of voltage gain(typically about 29db, about a 30-fold increase)from the power supply. The receivers which have a supposed "biamping" feature(among them most or all of the present Denons), apparently as an advertising gimmick, have only one amplifier(one power supply feeding up to seven output channels)and can't "biamplify".