Bass leaves after amp warms up?


I don't understand-after my Musical Fidelity M6i amp warms up for about an hour I notice the deep bass & kick drum aren't the same.
They sound less musical with loss of weight/depth.The notes are there but the moving of air have left.Sound is has much less impact and boreing.
I had the same problem with Bryston amp so there is no defect with amps nor with the rest of my equipment/
PSB Synchrony one speakers,AQ cables,Bryston CD Player.
My question has anyone heard similar & is there a plausable reason?
fishing716
It's possible that you're still young enough that your hearing extends up this high and you're bothered by the spike

I'm 53 years old
So you use the learning remote to mute the system, and then what? Does the sound change for the worse when you unmute it?
I didn't read all 250 posts. Did you try different speakers? Hopefully a different brand and one that has a warmer tonal balance. I still believe your system is going through its normal cycle, but where most people would say the sound improves your is going too far to the lean side. It doesn't take much in the way of warmth to make the bass sound dried out and make the music uninteresting.
It seems switching between sources or mute using the remote
causes a break in the circut.
When I release mute The fuller sound has been comprimised.
Sounds less like an audiophile system
I noticed sometimes while turning a record & putting needle down the same "distruption".
This dosen't happen all the time but enough to make me aware of it.
I always loose the good sound at some point
After using remote for the amp odd concidence that's when the sound may change
I haven't tried other speakers since I like PSB sound & look..But my second choice would be Joseph audio
I prefer not to advertise,box up & sell synchrony one's unless necessary.