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
Fishing, You've had so much good advice here, I believe the solution lies within. I don't think you should make any major decisions (like new speakers) until you've measured the SPL.
On the subject of amps into PCs, just FYI, my Sunfire manual states "do not plug the amp into a power conditioner."
If the digital was unplugged, seems like we can rule that out as being a problem.

Go ahead and restore the system.

I realize I made a poor assumption. I would not have turned off the amplifier when messing with speaker cables. Most transistor amps don't care, and our amps don't care, so I always leave them on.

The fact that they are getting shut down is significant. As I mentioned earlier, the fact that messing with the cables gets a response is an important clue; turns out the amps were shut down during this time! They have become suspicious again.

The only bugaboo is that I think we did a test where the system was played until the bass dried up, then it was turned off for a while and restarted. The bass was still gone. But maybe it was not shut off long enough.

Next time the bass dries up, shut the entire stereo off for about an hour, then see how it sounds.
Next time the bass dries up, shut the entire stereo off for about an hour, then see how it sounds.
That's exactly what I will try
Thanks
Unable to regain the bliss sound at all today
I may be abusing the system in different ways
Considering virtual yacht raceing