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 ain't over till the fat lady sings."

..without losing the bass and dynamics! :^)
Open letter to Dan @ Modwright
Hello Dan:
Thanks to Kristin as well
I have a long standing problem where bass is anemic sounding along with the rest of dynamics.
All of a sudden the bass comes through like a flood and the system sounds great.But it comes and goes throughout the day.
I have no explination & have changed eqiupment all year with the same result
Question
My speakers are 4 ohm and there is some debate on audiogon that these are difficult to drive.
Is that why your integrated amp doubles into 4 ohms
I currently have in my audio setup:
PSB Synchrony one speakers
Meridian 508.24 cd player
Rega P5 Turntable w/dynavector cart
Musical Fidelity M6i integrated amp 200 watts w/Kimber PK10 pc
DVD,TV w/cablew/
Audioquest comet speaker cables,biwire
Audioquest columbia interconnects RCA
Cablepro Revelation Power strip w/kimber PK14 pc
We designed the amp to double-down into 4 ohms because we wanted it to have TRUE power, capable of driving MOST ANY speaker. I wanted a beautiful looking and sounding integrated with POWER and available dig. and analog options to make a no-compromise integrated solution.
Thanks and in look forward to your reply.
Sincerely,
Dan W.