What's involved in dedicated lines

Gjkphd, I am so not an expert on this, it's ridiculous. But, here's my 2 cents:

First of all, if you have an old fusebox, & you plan to keep the house for awhile, it's probably worth it to upgrade to at least a modern 100 amp main panel w/circuit breakers, regardless of your audio issues. (Like Viridian said). Spending a lot of $$ on dedicated lines when you have an old fusebox seems to me like worrying about which Pirellis to buy for your Model T. But that's more of a homeowner's perspective than an audiophile's.

And yes, probably some things like a refigerator, or fluorescent lights, are worse to share the line with. (Hello!) But maybe tell us more about your system, your budget, etc.......

Gjkphd, like I said, my suggestion to change from a fusebox to breakers is more of a homeowner's perspective than an audiophile's. I honestly don't know how or if it would affect the audio quality. But I've been looking at a lot of houses to buy recently, & an old fusebox is definitely not desirable. Even 150 year old houses in nice condition will usually have updated electrical (circuit breakers). All I'm saying is, if you're going to spend $$ to get dedicated lines, when you're getting estimates, get a quote on this; it might not be more than a few hundred $$, & would be a nice update to your house, help the resale value, etc.

BTW, the fact that you have some 20 amp fuses doesn't necessarily mean they are on a "20 amp line". People use 20 amp fuses all the time (when 15 amp fuses are called for) because the 15 amp fuses blow when they plug in an A/C or something.

I realize this may be a bit O/T for your audio issues; just my 2 cents worth.