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
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.
Let us know results with the new amp and congratulations...
you reached 400 responses.
I've been having a similar problem, not only do I lose bass but the overall clarity drops. Sometimes my system sounds awesome other times not so much.
I believe I just found the problem, I wasn't sure if it was the amp or pre-amp so I ran the I/c directly from my Oppo to my amp. Flat sound no bass so it's the amp not pre. I wanted more volume so I reached around back & changed the input sensitivity switch, bass returned although the highs were a bit harsh. I moved the switch back & forth a few times & put it back where it was & it sounds great. Hopefully that's it & it will stay that way.
It's a McIntosh MC7270