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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
fishing716 OP
316 posts
 
Ralph after the bass diminished today I turned off the amp for one hr.
When I returned the bass was full & satisfying again

I believe this is the third time in a row that this procedure has worked.
I thought turning off my amp and fiddling with cables was the trick
Apparently turning of the amp was making the difference

I made it through an entire CD this evening before retiring.
And had satisfying bass most of the day
Clearly we're making progress

But something in the amp must be overheating for changes in the dynamics when warmed up.
That shouldn't be
rrog
1,958 posts
 
"Clearly we're making progress"

What progress have you made? I'm not seeing it. If you have an audio dealer close by I suggest trying a different speaker. Maybe your favorite stereo store will loan you a demo speaker. I have a feeling this problem will go away with another speaker.

I had a similar problem with a pair of Ruark Talisman speaker. I was driving them with a pair of Dynaco MKIII monos. After the system warmed up the sound became too lean. I replaced the Ruarks with Living Voice Auditorium speakers and the problem never revealed itself again.
georgehifi's avatar
georgehifi
10,312 posts
 
Fishing716. What I believe is happening is that when the amp is cold the bias is naturaly low, this does not tax the power supply as much as when the amp has warmed up, and the bias is at it's max adjusted setting.
However if the power supply is not up to the task it will sag on bass transients more when the amp is warmed up than when it's cold. As the bias is asking for more current when it's warm than when it's cold.

Cheers George
csontos
1,311 posts
 
Quiescent current is higher when the amp is cold and decreases as it heats up whether the outputs are mosfets or bi-polar. But more so with mosfets than with bi-polar outputs.
fishing716 OP
316 posts
 
You're right I haven't made any progress
The problem persists

I didn't expect to have a problem with such high end equipment.
Apparently what you say about the amp seems to be happening:

"if the power supply is not up to the task it will sag on bass transients more when the amp is warmed up than when it's cold. As the bias is asking for more current when it's warm than when it's cold".

I should either change speakers or amp right?
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