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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
bombaywalla's avatar
bombaywalla OP
1,958 posts
 
Larryi, Aball,

you guys have caught me on my symantics!! :-)

1stly, this IS a class-A amp. The manuf reassured me several times. I had similar doubts hence I did communicate w/ the dealer on this.

what I meant to convey when I wrote "At lower levels it takes a lot more time for the heat sinks to heat up" is that altho' I can feel the heat rising up thru the vents in the top-plate, the heat sinks are relatively cold. As the amp is played longer & longer, the heat sinks begin to warm up.
I agree with both of you that class-A amps are hotter at idle than when they are playing.
This bit of info was incorrectly communicated by me. Sorry!

Aball,
I have a Fluke thermometer that comes with a 2-pin fairly long probe. The probe end is a bit of exposed metal. I will have to look @ it to give you the model #.
So, I just stick the probe between the heat sinks or thru the top-plate vents to take the temperature.

Both heatsinks have identical support & air-flow around them.
shadorne's avatar
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shadorne
7,467 posts
 
Bombaywalla,

You should try to relax a little - I recommend Rockband - it is great fun through the main system (loud) - not audiophile sound quality of course but hit those drums and you will forget sound quality and just enjoy the music! They even have a song, which I suspect, may be just right for audiophiles such as you - Shirley Manson singing "I Think I'm Paranoid" ;-)
bombaywalla's avatar
bombaywalla OP
1,958 posts
 
Shadorne,

very funny!! ha, ha, ha!! :-)

OK, I get the point.
My inexperience w/ class-A amps "forced" me to ask the audio community at large.
Newbie to class-A cutting his teeth/getting his feet wet. Cut me a little bit of slack, chief!
jsd52756
420 posts
 
"If your amp is true Class A all the way, it will be
hottest at idle."
FYI - I have a Krell FPB300cx and it gets hotter the louder & longer I play it. It is aledged to be "Pure Class A" (key word here; aledged). I can play it at low volume for 10-hours and it stays cooler than being pushed. My point being, I question the above statement.
Good luck in your quest.
-John
elevick
2,636 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...).
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