Loss of bass & full spectrum sound

Kijanki has a line on some great ear buds on another thread.

I have fantastic equipment
No need for ear buds
Hope to try PS Audio P-3 power station
If it doesn't help I'm able to return for refund

It has been suggested to me by Ralph Karsten that the problems you describe could be the result of RFI contamination of your environment. The only part of your story that gives me pause is that the problem seems to show up after warm up. I don't see a tie in between that and RFI infiltration. However, I believe you stated that you live in an apartment which could surely be awash in RFI based on poulation density and neighbors using all kinds of computers/electronics with SMPS, etc.

I just wonder if there is any chance you might have a failing powwr supply capacitor in amp or source that begins to fail after a period of usage/warmup. I'm by no means a "tech" guy but it sounds like you are losing drive.

My Amp is Brand new(Musical Fidelity M6i) after replacing a privious brand new amp (Bryston B135).
It's unlikely the power supply capacitor is failing in my amp.
What you said about RFI is worth investgating
My prior statement that the system changes when warmed up was not accurate..
There is no reoccuring pattern when the sound will changes.
The kick drum & heft behind the bass lasts up to 72 hrs.

Has anyone tried Highwire powerwraps to rid RFI interference?

http://www.musicdirect.com/p-7195-highwire-all-clear-rfi-coils-pr.aspx

http://www.musicdirect.com/p-7194-highwire-powerwrap-ea.aspx