The circuit that the stereo is on has only 10 wall outlets on it and nothing else, There are 4 lamps besides the stereo plugged into these. The run from the panel to the stereo is about 40 feet with the stereo being the furthest thing on the run.
Given all this, do I have a fairly close to a dedicated circuit and the potential for fairly naturally clean power?
No.... A dedicated branch circuit is a direct run from the electrical panel to an electrical outlet.
What you now have is a convenience outlet branch circuit.
The electrician that made up the electrical joints inside the outlet rough in boxes had a multitudes of wiring methods he could use to feed onto the next outlet box.
The best way is to make up the hot and neutral wires and extend a pigtail out for the make up on the electrical duplex receptacle. But many residential electricians use the duplex receptacle for make up and feed the branch circuit wire to the next duplex and so on. Daisy chaining..... Some use the terminal screws for the feed in and out. Others use the stab in the back feature of the receptacle. This is the worst. Can and does create a lot of micro arcing AC noise.
Also your 40' run from the electrical panel to the duplex receptacle you have your equipment plugged into could be more like 50', 60' or more in length before it got there. And just guessing the wire size is #14 awg.
Would I benefit from replacing the outlets, and with what? Are there other things I can do that would benefit such as using a different breaker on that circuit?
Yes for the audio equipment. Good chance the existing duplex receptacle/s are residential grade at best 79 cent each.
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