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
I hear the "correct sounding bass like blood flowing through the music..My feet are toe taping & I am never figidigy..
After between 1 hr & 3 the sound changes and the patient no longer has the same "blood type"..
My toe no longer taps and it's not worth listening any more.So I would say the difference is like night & day.

Today after the desired sound left I waited a few hrs but it didn't return.

I pulled out the speaker cables on one side of the amp and reconnected the other side in it's place.
After 3 tries back and forth the bass returned in full bloom with one speaker connected.
I settle with this as I don't wish to risk blowing the found sound trying to have both speakers working.
But a major clue seems to be that I can usually find a way to get one speaker working with deep bass after losing the sound from one or both.
For some reason when the amp peaks after an hr.or so there is a distruption or short somewhere.
Like the amp or speakers need to reboot
I resent having to go though this nonsence daily
No way! Are the Bryston integrateds as muscular as a separate Bryston power amps. Call the factory and ask the techs. I can't go back to read all the steps taken to isolate the problem, but I assume working backwards you eliminated your source components (i.e., CDP and phono, as applicable), cables, etc.

If so, that could mean, as has been surmised above, the "true" impedance of your speakers may be lower than the nominal 4 ohms I seem to recall being mentioned. Actual versus "nominal" reported impedance stats can vary quite significantly and often do. Very few amps "like" driving into those kinds of loads. If a monster Bryston doesn't work, I think you go back to "Zeros" and see if that helps.

Btw, just an "fyi" I picked up some time ago when talking to Kal at ARC. He mentioned that ARC tube amps were used to drive Wilsons which have notoriously low impedance stats. Just an fyi.

Otherwise, as Al says, you have to consider the only remaining possibility, no matter how improbable: Poltergeists.

I'm going to see if your PSB speakers were bench tested by any of the reviewers. If so, I'll be back.
I asked mike at Bryston when considering Preamp BP17 & power amp 2.5BSST
He said they were the same as B135sst integrated in seperate boxes

Ok Fish..., here's what I got off the web.

HT Lab Test (12/07): The Synchrony One's listening-window response (a five-point average of axial and +/–15-degree horizontal and vertical responses) measures +1.18/–2.24 decibels from 200 hertz to 10 kilohertz. The –3-dB point is at 56 Hz, and the –6-dB point is at 50 Hz. Impedance reaches a minimum of 3.32 ohms at 70 Hz and a phase angle of –37.55 degrees at 27 Hz.

SoundStage (1/08):

http://www.soundstagenetwork.com/measurements/speakers/psb_synchrony_one/

The impedance magnitude and phase angle graphs are absolutely amazing!! I've never seen flatter. Problem is impedance over large swathes of frequencies is unbelievably low, especially in the bass frequencies.

Al and Ralph -- take a look at the graphs at the URL above. I'd like to read your thoughts about whether a solid state amp, or any amp for that matter, would get indigestion from those impedances. Fish ..., if Al and Ralph come back expressing concern, the Zeros are seriously looking like the solution.

BIF