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
Simply would like to know if anyone has experiencd even a noticable change of music being reproduced from one time to another?
It seems the symptoms I hear have no precident..
Which bothers me the most I think
I've looked on line + spoken to all the manfacutures of my equipment..Most won't even accept my calls any longer.
" I never ever listen to music loud"

Good to know. Its probably not the amp then.
Have you tried different speakers, as Kijanki thought you might have? And if so, did the same phenomenon occur with them?

I'm still suspicious of the possibility that the performance of your speakers is changing after they have been playing music for the hour.

Regards,
-- Al
I have seen cases where old switches in pre-amps or other gear cause a very significant loss of power over time as they oxidize, etc., and good contacts are lost. Same true with volume controls, balance controls, etc.

If there are any manual switches in play with your gear, next time you hear it, try twidling with controls and switches and listen for any differences. THe twidlling alone might help but if so a good cleaning is probably in order.

This happens with my old NAD 7020 receiver from 30 years ago that I still use. A few twiddles with the input switch on occasion when I notice things have faded out sets things right again until thenext cleaning of switches and controls. Not an uncommon thing...
I had PSB Synchrony twos now I have PSB Synchrony ones which are all around better when everything works.
Auditioned Thiel speakers for about a week but results were inconclusive

Could PSB being 4ohm possibly be the reason?
No one else has these symptoms & my dealer disputes this.
Ironically I keep buying PSB anyway..