Bass leaves after amp warms up?

Lets get back to the electrician visit....

When the electrician visited, did he monitor the power before, during and after you had these issues? If it included during your problems (what would be the point otherwise?), did he not hear the issues too?

Has anybody yet suggested cold solder joints somewhere in the speaker or DC saturated inductors.

When the electrician visited, did he monitor the power before, during and after you had these issues
NO
"did he not hear the issues too"?
No,I had deep bass while he was here
A few minutes after he left the bass changed
I called him back and he returned but was unable to hear the difference
The depth behind the bass notes was clearly diminished to my ears but not to him
So I guess draw what conclusion you seem appropriate..

Ralph after the bass diminished today I turned off the amp for one hr.
When I returned the bass was full & satisfying again

I believe this is the third time in a row that this procedure has worked.
I thought turning off my amp and fiddling with cables was the trick
Apparently turning of the amp was making the difference

I made it through an entire CD this evening before retiring.
And had satisfying bass most of the day
Clearly we're making progress

But something in the amp must be overheating for changes in the dynamics when warmed up.
That shouldn't be

"Clearly we're making progress"

What progress have you made? I'm not seeing it. If you have an audio dealer close by I suggest trying a different speaker. Maybe your favorite stereo store will loan you a demo speaker. I have a feeling this problem will go away with another speaker.

I had a similar problem with a pair of Ruark Talisman speaker. I was driving them with a pair of Dynaco MKIII monos. After the system warmed up the sound became too lean. I replaced the Ruarks with Living Voice Auditorium speakers and the problem never revealed itself again.