Great show as always, thought I would comment on the volume control of separates.
Any audio chain will consist of multiple gain stages. The user only cares about the total gain, total gain translates into SPL at the output of the speakers. In separates the power amplifier will have a fixed gain, and the preamp will have variable gain. So the preamp will adjust its output signal to appropriately drive the power amp given the fixed gain of the power amp.
AV receivers have this same setup but the "preamp" section sits right beside the power amp, they will NOT change the gain of the power amp. basically when it comes to the volume control separates and a receiver are exactly the same.