Bass leaves after amp warms up?

I may have missed it among the 140+ responses, but did anyone suggest you run an extension cord from another part of the home to the amp? Perhaps the circuit breaker or the wiring/panel/outlet has a resistance and after an hour of high current from the power amp the thermal resistance is increasing, therefore limiting the bass notes. Notice that the phenomenon took longer with only one channel driven ( as the single channel driving a speaker will draw less current from the wall, but problem still occurred later, nonetheless). Adding a powered sub to the circuit will exacerbate it as another amp is being shared with the AC, no?

3 amps with exact same issue rules out the amps for sure, plus as I used to repair Musical Fidelity, I know the M6i runs very cool (if properly biased), and is Bipolar transistor powered. Removing the cover would be not help if the amps cover is cool to the touch. Plus, I know the M6i is fine with 4 ohms; all day long.

Hope this helps.

Steve

I have tried every outlet in the apartment with same results.

Mcintech,

Curious what your assessment of the MF amp into 4 ohms is based on?

I think we have seen where the OPs PSB speakers present a challenging load even lower than 4 ohms at some points but nothing that indicates the MF amp is up to the task of driving them well without running out of gas, which seems to be what is happening for some reason.

Thanks.

Mapman
You're assessment may be the correct one.
As I have tried every variation imagionable.
Two reasons that keep me hopeful:
I am satisfied with PSB Synchrony's overall balance with my system & would like to keep them.
It seems improbable the the manufactur nor any other user of these speakers can identify with this problem.

Fish,

Can't you get your dealer who sold you the amp and/or speakers to help you sort through things?

You have a nice published resource here in this thread for reference, with feedback from various knowledgeable members, to help them help you sort through things and cut to the chase, which in my opinion means as a next step being able to try an amp that is better suited to drive the speakers on paper WITHOUT ANY QUESTION BASED ON KNOWN/PUBLISHED AMP SPECS/MEASUREMENTS.