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
Don't know. Since it is a British manufacturer, they might be metric. If they require an Allen wrench, this writeup might be helpful, as it indicates which sizes are and are not interchangeable between millimeter and inch-based sizes.

Regards,
-- Al
Ant
Please don't listen to these guys and remove the top
cover to the amp you could get shocked.
wait for the electrician to show up
Best JohnnyR
Yes, I should have stated the cautions that the amplifier should be unplugged from the AC when the cover is being removed, and nothing internal to it should be touched whether it is plugged in or not.

Regards,
-- Al
I would not have plugged it in or touched inside.
Was unable to find a tool to try instead took shelf off above the amp for more ventalation