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
Glad you like the Power 1. I really like mine as well. I may consider getting the MK 3 some day for its headphone amp capability. Have you had a chance to try it out yet?
Accustic Arts/psb/sony/rega photo:
http://forum.audiogon.com/cgi-bin/fr.pl?vdone&1372392821&view
Yay, I detect a happy customer.

Wait till he see's the high priced consulting bills we're all about to send him.....

Especially Al's!
Does Accustic Arts have distribution in the US? I guess it must, but I can't seem to identify it.