auxinput
I would like to comment on your response above.
The offset in a power amp has nothing to do with whether it uses bipolar or MOSFET or any other transistors. It depends on circuit topography and how much DC feedback is used (or if servo amps are employed as in Parasound amps). If you are referring to Vbe matching, bipolars might be better than MOSFETs but that depends on the type and manufacturer.
While using a large number of output transistors reduces the load on each transistor, the downside is that a large number of transistors create a high capacitance load for the driver stages, slowing down the amplifier. This high capacitance reduces the slew rate and can create TIM distortion. In my amp designs, I prefer to use the smallest number of power transistors possible that will get the job done and not experience secondary breakdown under full output current or high bias conditions. This is particularly true for bipolar output stages and less to MOSFET output stages.
You are correct in that a large number of bipolar output transistors can experience current hogging if the thermal environments are not identical, even if they are closely matched for hfe or other parameters. This is another reason to stay away from large numbers in the output stages. Also, with a large number of output transistors, if one fails it can take all the others with it, as the remaining transistors cannot handle the increased current load and fall into secondary breakdown. This is what often happened in the old Phase Linear 400 amps back in the 70's ands 80's.
Regarding the sound aspects, perhaps they exist as with other components, but the design parameters such as the power supply, driver circuits, amount of feedback, etc probably have a much bigger impact. You very rarely hear of power transistor "rolling" as with tubes.
