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Hey guysso I'm using at the moment this lovely Sony TA-N86B power amp.
I used the switchable "pure class A" mode (2 x 18watt class A instead of 2 x 80watt class B)
it's been working great in winter and spring but now that summer is there it keeps shutting down... after a few hours being on, even if i'm not playing music, it shuts down by itself.
I suspect the room temperature is too high for the amp to cool down and the protection circuits kick in.
Due to a mod in the PSU I cannot switch the amp in class B mode anymore (even if it would still be possible, it sounds soooo good in class A i wouldnt want to).Is any of you experiencing the ame kind of problem with Class A amp during the summer?
Would a few computer fans strategically placed under the radiators be a possible solution? I don't really want to put a big, noisy fan next to the amp all the time.PS I don't live in a tropical coundtry (Belgium) but the apartment is full south oriented and gets too much sunlight during the day, making it very hot...
Edits: 08/03/14Follow Ups:
I suspect the bias has gone too high, pots need to be rotated back and forth a couple of times just to clean the resistive track, then set as per attachment for bias adjustment, only attempt this if you are confident.Cheers George
Edits: 08/05/14
A single fan should take care of the problem. It is surprising how just a small amount of moving air can help a heatsink.
Did the amp work fine, in both Class A & B mode, before the modification?
it needs to be recapped and re-bias...
If a thing's worth doing, it's worth doing well
(Proverb)
The amp was the property of an electronic technician who builds power amplifiers as a hobby.
Mod consisted in the replacement of the original power supply with a new high specs one (the original kept failing); the amp has been completely recapped with high grade capacitors, fully tested and biased. But it's possible he did somethiong wrong. It sounds so incredibly good tho I doubt there's anything wrong with the mods... I guess it's just the room temperature that's really too high...
I have 3 Antec "Truequiet 120" fans on my gear. They are almost silent. With everything in the apartment turned off except the audio gear, I can't hear them at all unless I get my ear about 6" from a fan, and then it's really a whisper. They don't move a lot of air, but it's enough to make a difference, especially for the preamp which is in a fairly confined space.
They are designed for computer cooling, so you have to get a wall wart and splice the power line to it.
WW
"A man need merely light the filaments of his receiving set and the world's greatest artists will perform for him." Alfred N. Goldsmith, RCA, 1922
Too hot for the amps cooling system under the circumstances.
Funny thing about Class A amps is that they dissipate more heat at idle than at full power.
There is not a lot in it but the louder you play your music the cooler the amp runs.
A few silent computer fans aimed at the heatsink(s) may well do the trick.
"Funny thing about Class A amps is that they dissipate more heat at idle than at full power.
There is not a lot in it but the louder you play your music the cooler the amp runs."
So what you are asserting is, if our Belgian friend would like a cooler running amplifier, he should run it at near clipping all day long to keep the amplifier "cool." He could do this easily with a test CD like the Stereophile CD that has test tones. He could disconnect the speakers and use a dummy load for those times he is not using the amp and run it full output into the dummy load hour after hour to keep it cool.
Since this assertion is clearly counter-intuitive, I think it would be a great service to us all if you could describe to us in technical terms why a class A push pull amplifier draws LESS current when passing a signal and the lowest current draw when operating near clipping.
Thw writer is correct.
First the anecdotal evidence. We have a Yamaha CA-800 integrated amp that's switchable into class A. It runs hottest at idle and cooleer the louder it's played. We played it loud for about an hour once and it's the coolests it's ever been after being on for a while.
Second: Class A amps dissipate a constant amount of power. The louder they're played the more of that power they dissipate in the load (the speakers) and the less in themselves. They also draw (nearly) constant current and power from the wall. You can check that with a Kill-a-watt or other such device. In fact that's the easiest way to check whether a claimed class A amp is truly class A.
We had a Bedini "Class A" amp in some time ago that didn't sound class A and didn't measure class A. I suspect it used some sliding bias technology and/or sliding rails to claim class A.
Class A is woefully inefficient and generally really good-sounding.
"Class A amps is that they dissipate more heat at idle than at full power."
"Class A amps dissipate a constant amount of power."
These statements are mutually exclusive. The first statement violates the definition of Class A the second statement is correct.
This statement violates the second statment:
"The louder they're played the more of that power they dissipate in the load (the speakers) and the less in themselves."
Say a given Class A amp draws 300W of power from the wall socket.
It will always draw 300W if idling or close to clipping.
When idling all of those 300W get turned into heat, when it is playing some watts go to the speaker and the rest gets turned into heat.
Hope you get the idea because I can't really dumb it down any further but none of the statements violate each other. Kinda obvious if you think about it.
You may need a separate Summer Amp, like some Tube owners.
Long Live Adolph Sax and Hercule Poirot !!
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