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Old 2nd June 2004, 11:56 PM   #1
Magura is offline Magura  Denmark
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Default How do you deal with the heat??

I had a question popping up yesterday.

How do people living in warm climates deal with the heat dissipation of a class A amp??

I know that in Brazil 45C indoors is not uncommon, thats like 15 to 20 above what we see in this end of the world.

All of a sudden 40C over ambient turns scary

Magura
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Old 3rd June 2004, 12:23 AM   #2
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Water cooling? Air conditioning? (The only way..) Put the amp outdoors, out of sight out of mind? From an engineering standpoint, it doesn't matter at all as most devices are rated to 175°C.

Tim
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Old 3rd June 2004, 12:47 AM   #3
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Talking Do whatever it takes.

I was once DJ'ing a house party (1985), about 120 people, when a guest came over to me to tell me one of the speakers was really badly distorted.
We had set up multiple amps feeding stereo sets of speakers in in each of several rooms, this was a loud party.
What I found was two speakers were really badly distorting so I ran back to my amplifiers and found one just cooking like crazy, so I shut off the offending amplifier and opened the window beside where I was stationed, and placed the hot amp outside on the sill, where the temperature was a pleasant balmy -38c (super dry Manitoba Canada winter), within about 10 minutes I turned on the amp again and it gave me no further problems all night as long as it was sitting out on the sill.

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Old 3rd June 2004, 01:05 AM   #4
SY is offline SY  United States
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From an engineering standpoint, it doesn't matter at all as most devices are rated to 175C.
Except for the listener.
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Old 3rd June 2004, 01:09 AM   #5
sam9 is offline sam9  United States
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How about using a Self Trimodal? -- in summer you can switch it to class B. It's only available in kit form as far as I know.

Another dumb idea: you could cut an small rectangle in your outer wall and slide the heatsink through leaving the cool part of the amp indoors.
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Old 3rd June 2004, 01:34 AM   #6
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Default Blow on it...

I built a Class A headphone amp, and using a thermocouple I measured heatsink temps of 70 C, at 25 C ambient. While the parts can withstand that, it bothered me. Plus, the heatsinks were really too warm to touch. The solution was a fan. I found a small 5 volt DC fan, which I run at around 4 volts to keep the acoustic noise down. The heatsinks barely get above ambient now. There is some noise, but in the lab, with lots of test equipment running, one tiny fan isn't really noticeable. I wouldn't want it in my office, however.

Even a small amount of airflow can make a huge difference in heatsink temperatures. I've done a lot of thermal measurements, and it's really amazing how much difference a fan can make. Unfortunately, fans are not always an option in the stuff I work on.

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Old 3rd June 2004, 02:49 AM   #7
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Default Is not common 45 degrees in Brazil

Temperature normally goes from 22 degrees to 30 degrees in summer.

In winter you have lower temperature, and sometimes we have snow in extreme south.

And, "end of the world", depends of the extreme you are....maybe, near North Pole can be the end of the world for some people.

Of course, automobiles exposed to sun, can be more hot.

Also places with bad air flow, of course if you measure a metal sheet can be some degrees up...but when air temperature reach 42 in those stupid thermometers we have in the streets, were sensor is inside metal shielded cabinet, without air flow, government order to stop all kind of work because dangerous to health.... i remember it happens once in my 52 years old age.

Please, when temperature goes down in Denmark, to protect citizens government order you to stay home?

Better to think a little more, wheres the end of the world.

Carlos
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Old 3rd June 2004, 02:55 AM   #8
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simple... you design an amp with twice as much heatsinking, so its only 20degrees above ambient.. so on those 40 degree days, when the air conditioning breaks, and the room temperature is slowly creeping up, you can atleast run the amp for a few hours before it gets hot enough to boil water on..
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Old 3rd June 2004, 02:59 AM   #9
grataku is offline grataku  United States
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Quote:
Originally posted by Sch3mat1c
From an engineering standpoint, it doesn't matter at all as most devices are rated to 175°C.

Tim
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ever heard of thermal runaway and positive temp coefficient? Just because you like to melt stuff not everything is a damn crucible.
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Old 3rd June 2004, 06:17 AM   #10
sam9 is offline sam9  United States
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"I built a Class A headphone amp, and using a thermocouple I measured heatsink temps of 70 C, at 25 C ambient. While th. . ."

I did a headphone amp with a pair of MJE340/350 outpt devices. In free air and no sink they stabilized at ~95 degC. Adding sinks (ittiy bitty 1"x1"x1") brought that down to ~55 degC. Maybe in the summer I should bolt on a bigger sink if there is room.
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