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

A little backstory for the curious: When I moved to my current house, my audio quality decreased substantially. I spent a great deal of time investigating this and believe I’ve narrowed it down to the AC main. Multiple electricians have failed to find anything wrong with my electrical system or electrical panel. At this point, I believe the power quality from the city may be poor but I’m not sure how best to measure it. I also have a hunch that there is a loose connection somewhere between the utility transformer and my breaker panel. Before I bug the city, I would like to be able to provide measurements that something is wrong, but I don’t know how best to do that. Also, from a recent utility locate, it looks like the underground power goes from the transformer to my neighbors house and then to my house. Is that standard wiring procedure?

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.

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.

I don’t think the electrician did any of that. I should have hired you! I think it was more of, “Well I tightened what lugs I could and no breakers are flipping so you don’t have a problem.” Thanks for all the good advice.

Just wanted to say thank you to everyone that replied. There is a lot of good information here and I’ve got some good paths to go down. Will definitely call my utility and follow up on that.

Thank you for sharing your experience. Clean power is vital!

Quick update: I called my utility company and they sent someone out immediately. They discovered that the neutral lug on the homeowner side of the meter was loose and the bolt is stripped. An electrician is on the way to replace the neutral lug. 

They tested the line from the street to my meter. I don’t know what they tested exactly. Is that the same thing?

It’s fed underground. 
Another update:

The electrician came out and repaired the bad neutral lug and tightened everything up. The utility turned the power back on. The first thing I did was run some “tests.” Dimmable lights that used to buzz loud are quieter, the treadmill no longer dims the lights with each footfall (it does a little bit but it seems normal now whereas before it was like being at a rave), and best of all the sound quality of my audio system improved! No wonder - I’m sure the current flowing through the bad neutral lug wasn’t helping in any way with power delivery!

I’m really glad I put in the effort to follow through on this. I am very thankful for all the good advice from this community! I knew something was wrong with the power. I am happy that I didn’t go off on tangents with dedicated lines or power regenerators. I still plan on doing those things, but they would not have completely solved my problem in this case.

Interesting. I am in the same situation as you. I have a couple SMPS’s on the same circuit as my other gear. I could power them off a 12V battery using a 120V AC inverter or run a dedicated line for them. I wonder if my amplifier would sound better without those SMPS’s on the same circuit. I also wonder if they interfere with each other.

Power regenerators do absolutely nothing for sound quality unless your components are very poorly designed.

In my experience, everything is on a spectrum. It’s not binary. Clean power is very, very important. Every time I’ve cleaned up my power in any way, I’ve experienced positive results. The better designed equipment didn’t benefit quite as much as inferior designs. In the end, it’s up to the listener. Does a specific power upgrade provide enough benefit to justify the cost?