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
Ralph, I need to state that the bi-polar amps I have do in fact reduce current when hot, however not as profoundly as the mosfets do. But I don't think it's an 'overheating' issue at all. Simply an incidental one in that because the outputs are operating under an optimal (factory) setting, the difference in performance from cold to hot is more pronounced.
No proof this is the case but I would be willing to wager bias is set to a conservative sub-optimal level in any brand new ss amp. Whether this is what the op is experiencing is imo unclear.

Csontos and Ralph,

So, if I'm understanding what you're saying, some amps sound better cold than when they're warmed up? If that is the case, anyway it goes, it seems that a person needs to leave the amp on and accept the way it sounds warm.

That is, unless you want to listen for an hour, turn it off, let it get cold again and then turn it back on and listen for another hour. That just doesn't seem to be an ideal way to listen to your system.

If a warm amp is at least consistent even if it doesn't sound as good, at least you have a known sound that you can count on.

Am I thinking wrong?

Chuck
You got it! Unless of course you decide to either set up the amp optimally yourself or have it done if you're too squeamish. If you do, you won't be complaining about the issue I brought up and you can go ahead and leave it on 24/7.
I've been following this OP with fascination. I'm going to record my stereo too. ;>') Kidding.

Bottom line: should Fishing simply turn the volume up to get to the sweet spot?? If so, 300+ posts later, it sounds like a pretty simple solution. I surmise that Fishing won't need Zeros. Just a remote control to increase gain by roughly 3 db after warm up.

It's actaully quite interesting to me. By contrast, tube amps usually sound better after warm up. Is this a common problem with most SS amps? If so, I wonder why more folks don't raise the same issue??