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
I saw that you had listed your system for sale. Did you get to the bottom of the problem or have you just given up?
Fishing716... understandably you're selling the amp, but why the Synch One's?
He might be giving up which is understandable after a year of HiFi Hell, but I think he wants to start over with a different system. He obviously had a bad match. This is a common problem when reading reviews and assembling a system based on magazine recommendations.
The OP'r has a post in another section asking about headphones. Maybe he has decided to take another approach to enjoying his music.

Either way I hope that he can get back to enjoying the music instead of wrestling with his system.
Currently listening to Denon 1650ar cd player w/grado headphones-
I've been getting the music message this way.
I'm switching to Bryston separates w/Synchrony One's
If this don't work,options to try:
Different brand of cables than Audoquest
8ohm speakers @ Joseph audio
Differnt living situation
Thanks for everyone's patience w/numerous posts.
I've considered there may be a defect in my judgement.