Thank you for looking at my question. I have an electronics background from the military but I'm no engineer. I am trying to design a sound system with remote wired volume control in a chair. There are three separate amplified audio events going on at the same time. What I am trying to do is have one audio signal source in stereo going to three distinct level controllable outputs. Two at about 100 watts each and the third going to a smaller amp for speakers near the ears and I am trying to put separate volume controls for all three channels on the arm of the chair. I am confused about the most efficient way to control my output volume. I know the wasteful way is to simply put an inline potentiometer on the speaker output of an audio amp like speaker selector switch boxes with volume control. I have seen devices that take line in and have volume control on the line out to an amp which is cool but then do I run that to an amp that is set to a high volume level? Seems like that would burn power with the volume down as well but not as much. How is it done in things like audio receivers? When the volume is all the way down everything is super quiet. When you crank the volume up with no input signal you hear a slight hum or hiss but with the volume down everything is dead quiet. What is the volume control doing in that case?
Without doing any real engineering, those in line volume control potentiometers might actually not be such a big deal, provided you insert them in the correct location.
See, the input to most amplifiers is high impedance - meaning, essentially, that it won't draw much current. Using a potentiometer to attenuate the line before the amplifier is a quick and dirty way to get things done, but as far as waste goes, losses around the potentiometer would be fairly minimal.
For several reasons, you certainly do not want to use this hack between a power amp and the speakers. That would be quite wasteful indeed.
When those amps are cranked up, that hum is simply the amplifier doing its job on a signal that probably came from a mildly noisy component or connection. Everything has resistance, and all resistance experiences thermal noise. It could also be power supply noise or a number of other things, but it can only be removed by careful design. If you use the inline volume control, there will now be an additional source of noise that may or may not be tolerable.
For other options, I'm honestly not sure of many other than buying or building a low distortion power amplifier to serve as the input stage to your last power stage. Fortunately, the kind of small one you would need for an intermediate stage can be fairly cheap, since all the heavy lifting is done further down the line.