How To Do You Measure the Quality of Your AC Power?

Maybe, but maybe not. What I have noticed about electricians and electrical engineers is that they approach it from the perspective of meeting code and not starting fires. That’s not a bad thing in general, but if you’re chasing high fidelity sound you’re going to have a bad time with that approach (minus the not starting fires goal, haha!)

If code allows for a 5% voltage drop in a 120V line, then you’ll see fluctuations between 114 volts and 120 volts depending on the load. That’s completely unacceptable for hi-fidelity sound. You want that voltage sitting at 120 constant and not budging an inch. Sure, a good power supply will minimize the effects of voltage fluctuations but why would you want to deal with that hurdle if you don’t have to? Make it as easy as possible for your equipment to perform, which means going well beyond what a code book would tell you. 

Your advice with a dedicated line is spot on, however, it won’t fix problems upstream of your panel such as a loose lug on the meter socket. There are other things going on outside of my audio system that strongly indicates a poor ground or bad neutral connection.

I could pull a dedicated line, I could buy a filter, I could buy a regenerator, and I probably will some day, but there has to be a better method than “just try whatever and see what helps.” If you can diagnose the problem properly, then you can apply focused solutions which saves time, money and headaches.

Early in 2020, on the recommendation of my electrician and @jea48, I contacted our Power Company and requested a power quality analysis. They installed a special meter and downloaded weekly readings for a month. It resulted in some repairs to our service, and to neighbors’ service. One repair improved voltage consistency. 

It was free. Well worth investigating.

That’s exactly the type of thing I wanted to hear about, tvad. Thank you!

Besides poor audio quality, two examples of what I’m experiencing are:

1) Playing music with bass at low to moderate levels causes dimming lights.
2) Slowly walking on a treadmill causes the lights in the room to substantially dim with each foot step.

I’ve had electricians tell me that the best way to wire things is to have the lights and outlets on separate circuits so that things like treadmills don’t dim the lights, but there’s just no way a slow paced walk on the treadmill is pulling down the voltage that much on a normally functioning electric service. The problem seems to affect the whole house which makes me think it’s upstream of my panel. I’ve had all the lugs in my panel tightened and I even dug up the top of the ground rod to verify it’s connected and it is.

What a freaking waste of time and money. None of these people will find anything wrong, because from their point of view there is nothing wrong.

Multiple electricians have failed to find anything wrong with my electrical system or electrical panel.

Exactly. There is nothing wrong. Sorry, but there just isn’t.

Qualifications of the electricians? Years of experience in troubleshooting?
Were the electricians just residential electricians, or journeyman electricians with years of hands on practical experience troubleshooting electrical problems in commercial and industrial facilities? Yeah, it makes a difference.

Here is what an average electrician should do, and check for, in an electrical panel.

1) check voltage. Line to Line and each Line to neutral. He/she should also check Line to EG bar voltage to verify the Main Bonding Jumper is effectively bonding the service entrance neutral conductor to the metal enclosure of the panel.

2) Hopefully the electrician has a Thermal Imaging Camera to check for corroded and or poor electrical connection hot spots. Or maybe he/she just has a cheap temperature sensing handheld device for checking for hot spots. (All loads should be turned on if possible. Especially high amperage usage loads).
Corroded and or loose connections can cause series light arcing which in turn can cause harmonic distortion on the mains. Even bad seating contacts in a breaker(s) can cause harmonic distortion on the mains. That also goes for the Main breaker. Same goes for the Line side connection of the breaker to bus tie connection.
Did any of the electricians have the equipment to test for temperature hot spots MC?

3) If no hot spots are detected the electrician still should look for any signs of corrosion at all wire to breaker terminations. Especially on the service conductors feeding the main breaker or main lugs, if the main breaker is elsewhere. You would be surprised how many service entrance conductor terminations at the electrical panel show signs of corrosion.

4) The electrician should check the Grounding Electrode System for corrosion and tightness of all connections. (Grounding electrode system is the wiring and clamps used to connect the service entrance neutral conductor and service equipment enclosure to mother earth.

5) If the panel is fairly old and has aluminum bus the breaker to bus tie connection should be checked for possible burn arcing hot spots. Especially known loaded branch circuit breakers.
Go through all the electrical connections in the panel for wire to terminal tightness. Conductors to breaker terminations. Neutral conductors to neutral bar terminations. And EGC to EG Bar terminations. Check tightness on service entrance conductors at main breaker or main lugs. Check service entrance neutral conductor lug for tightness.

FWIW I have read at least 4 threads on various audio forums over the years where the OP asked basically the same questions as the OP on this thread. In the end the problem was found in the meter socket of an overhead fed electrical service.
Rain water over the years can find its way through the weather head and inside the mast conduit and travel down the conductors and collect on the Line side of the termination lugs. Over the years the water causes corrosion and causes the connection to deteriorate. That in turn causes a small amount of series arcing in the connection(s). That in turn causes harmonic distortion on the mains. The greater the connected load on the corroded connection(s) the greater the percentage of harmonic distortion on the mains.

It won’t cost the OP a PENNY to call the Utility Power Company. Just a little bit of his time.
Or just take the advice of MC. He will tell you "He is the only one here that has actually done it".....  

Best regards......