Thanks for all the suggestions and comments. Alas, we are still in the process of elimination. Since my OP, the electrician has retraced every step and assured proper connections and grounds, etc. Importantly, he has checked the voltage with a fancy device and reports that voltage is exactly 115 with only tiny (non-material) variations. Extension cord running off different circuits produced no improvement. So, we have ruled out house or Maine Central Power as the cause. (Note, however, that this home is at the foot of a mountain, gets hit hard by storms, and the locals tell me three weeks ago the thunder and lighting in the area were epic.) Next, in the system, I replaced the CDP source, but no change. As I see it, that leaves two candidates: (i) McIntosh C2500 pre-amp (correction from the OP, its a C2500 not C52 -- I had an early senior moment) or (ii) MC452. It being the weekend, I wasn't able to talk to McIntosh to get guidance on which might be the target. So I rolled the dice and am shipping the C2500 in for a check up (couldn't deal with packing up the 110 lb beast). Fingers crossed its the pre-amp, and can be a quick fix; I am having the wife's family up for the Fourth and desperately need the rig in full throat to drown out the sister in law's non-stop mouth.
Need Help: What In My Home Electric System Killed the Sound?
Could really use some troubleshooting from you electric experts out there, of which I certainly am not one. House is in rural western Maine. My electrician (licensed and very experienced, but not in audiophile context) is running a dedicated line to the 2-channel rig. He installed the new line up to the outlet, but didn't complete yet (we're waiting for delivery on the outlet), so the new line is temporarily capped off at the wall. In the meantime, elsewhere in the house, he changed a broken recessed light socket and changed the related wiring to that light. Those are the only two changes to the electric I am aware of. The 2-channel system remains plugged into the same outlet we've been using for years (until the dedicated line is in). This weekend, the life is gone fro the system. For example, volume at "25" on the pre-amp would normally be quite loud, but now it needs to be turned up to 40 to get the same loudness. Regardless, dynamics are gone, tempo is a tiny bit slow and has lost toe tapping, and vocals moved from near field to way back in the mix. Nothing was changed in the system (Rega Saturn CDP; McIntosh C52; McIntosh 452; and Polk SDA 1.2 TL (heavily modded)). Any thoughts on what might have cause these symptoms? Electrician can't pinpoint anything. Any input appreciated.