Bass leaves after amp warms up?

I would ask suggestions for more efficient integrated amp to drive PSB speakers..

There are many well received integrateds out there these days that use CLass D amplifiers, even inexpensive Japanese ones from companies like Onkyo. Quality of power supply, which matters might vary widely with an integrated more so than separates. If the specs indicate mostly doubling down to 4 ohm, it is probably worth consideration. There are still limitations with amp and pre-amp in close proximity in same box with Class D, but technical aspects relating to noise and shielding are different. I have not used Class D integrateds so cannot vouch, but many have received good reviews and acceptance. To be safe, I'd say separates are better (and with Class D amps smaller as well). But why not try a well reviewed integrated for reasonable cost first and see? If it does not work out then move on eot separates. I think there is a decent chance the right integrated could work for OP.

The voltage is normal
By the end of the day there is nothing left in the bass dept.
I turn off the amp for the evening and return in AM
Plenty of deep bass & sounds excellent
I listened to Abbey Road this morning but by the end of the first side
McCartney's bass lost his groove.
I didn't bother listen to the second side.
Sometimes I switch speaker cables from L/R to R/L
And lower bass returns for an hour or less.
It's quite a dilemma

OK. Based on the testimony so far we can safely assume that hearing has nothing at all to do with it.

I am also doubting that the interface between the amp and speaker is an issue. If it was, the bass would be a problem as soon as you turned the amp on. So that is not it.

The only clue we have is that doing something with the speaker cables sometimes has an effect. Letting the system cool off does not.

If none of *that* has any effect then I become more suspicious that its not the amp/speaker setup at all. But- the fact that moving the speaker cables has an effect is an important clue. Let's start with the recommendations above and see what happens.

At this point I would be looking at the cables. How long are they? How tight are the connections at either end? After listening until the bass dries up, is there any heat on either end of the cable? It might be as simple as a loose connection.

FWIW, speaker cables become very critical when used with lower impedance loads! If your connectors are only finger-tight you are missing a bet. You should get the connections as tight as you can without damaging them. I usually use a small wrench to tighten things down. That can have a big effect on bass, especially with lower impedances.

Its also true that you really should not run speaker cables longer than about 5 feet if you have low impedances in the speaker.

04-11-13: Fishing716
After enjoying the system sounding great for 2 hrs the bass dried up. I waited 1 hr.tried again but no improvement. Turned off amp for 1hr.returned & the presentation was still awful. I also observed when I change source on the amp it seems to create a break in the circut & the bass leaves soon after. I've sometime observed after turning a record around/changing channels on a cable box or changing imput buttons on the amp may upset the delicate balance.

04-11-13: Fishing716
Disregard previous post: Makes no sense!@ But there is no pattern when system sounds optimal: Could be am or pm

04-12-13: Fishing716
Sometimes I switch speaker cables from L/R to R/L
And lower bass returns for an hour or less.

04-12-13: Atmasphere
The only clue we have is that doing something with the speaker cables sometimes has an effect. Letting the system cool off does not.

Not sure that we can say that conclusively at this point, Ralph, although the checks you suggested of the connections are certainly in order. I believe it was only one experiment that indicated that letting the system cool off did not result in recovery, and the report about swapping the speaker cables included the word "sometimes." I would be hesitant to conclude at this point that those results would be consistently repeatable over many trials.

Presumably the amp was turned off when the speaker cables were switched, and perhaps the recovery was actually the result of it being allowed to cool off. Or perhaps it resulted from something else that occurred during that time.

Also, I would repeat my suggesting of trying, as an experiment, running the amp with its top cover removed, if that is practicable.

Concerning candidates for possible replacement of the integrated amplifier, while I'm not particularly familiar with the integrateds that are out there these days, my feeling is that finding one that can deliver 100 or 200 watts or more, provide good sound quality, be able to handle 2.7 to 4 ohm impedances gracefully, and cost in the vicinity of the $3K or so price of the M6i, is likely to be a tall order.

Personally, I would go with a separate power amplifier, driven from the pre-out terminals of the M6i.

Regards,
-- Al