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For people with experience with Class-A amps

Hi All,

I had a question for all you audio folks who have experience with Class-A power amps as I am new to this myself.

This is bugging me so I finally decided to ask - I have a class-A power amp (name will be with-held to protect the innocent) where I notice with no shade of doubt that the right heat-sink is warmer to the touch than the left heat-sink after about 2 hours of play/program material.

I got hold of a thermometer & measured the heat sink temperature (stuck the thermometer probe deep into the heat-sink fins & waited for the temperature read-out to increase/decrease by 0.1 degree Celcius).
What I found was that the right heat-sink was 1.5 - 2 degrees Celcius HIGHER than the left heat-sink. I have about 4 readings so far. Altho' not a lot of data points, each measurement has the identical trend - right heat-sink was 1.5 - 2 degrees Celcius HIGHER than the left heat-sink.

This indicates to me that the right channel current bias is more than the left channel current bias. Am I correct in my thinking?
2ndly, should I be worried about this?
(in that, over time, this temperature differential could diverge & the amp could run away thermally?).
Should I get the dealer to adjust the bias so that both channels are more or less equal?

I realize that "more or less equal" is a fuzzy term. To that effect, in your respective experiences, what should the temperature differential be between the 2 channels? 0.5 degree Celcius? Less? More OK? if more, upto what point OK?

Thanks very much in advance for your help.
128x128bombaywalla

Showing 2 responses by elevick

elevick
2,439 posts
 
John,
That's the opposite of Class A. Class A amps are so good because they are always running at full power. The power has to go somewhere when not being used for sound, hence the heat. As you play louder, the heat dissipation reduces.
The Krell may sound better than many class A amps but it not. I'd say that Krells are very nice but not as "warm" sounding as Class A amps (pass, threshold, aragon...).
elevick
2,439 posts
 
Could be many reasons. Have you opened up the amp? Maybe things are not symetrical inside?
Are your speakers drawing the same power? Check the impedance on them?
Is this difference when listening quietly or loud? Most class A amps will switch to B when pushed hard. They tend to only be class A for the first 10 watts or 10% (not all of them though).
Is your pre-amp the culprit? Is the balance off or is the sound even out of both sides? and on and on???
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