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
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
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.
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.
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.
Pic of amp:
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.
Pic of amp:
Attachments
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
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
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..
"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.
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.
Grataku >> 
That's why you prevent runaway. GC's and Pass Labs stuff must not be designed too well if you're worried about that... (But look at me, I work with tubes, I don't know the meaning of tempco! )
Pulling up a schematic for 2N3055 it says junction/storage temp max. at 200°C, so given around 1.5C/W junction/case you can run it up to 155°C (case) with 30W through it... 'course life will be nasty at that toasty pace, but it comes to within the datasheet figures so I've reached my point.
Not that I'm saying anyone should run stuff that hot... I wouldn't run anything hotter than 100°C. Besides tubes that is
Tim
That's why you prevent runaway. GC's and Pass Labs stuff must not be designed too well if you're worried about that...
(But look at me, I work with tubes, I don't know the meaning of tempco! )Pulling up a schematic for 2N3055 it says junction/storage temp max. at 200°C, so given around 1.5C/W junction/case you can run it up to 155°C (case) with 30W through it... 'course life will be nasty at that toasty pace, but it comes to within the datasheet figures so I've reached my point.
Not that I'm saying anyone should run stuff that hot... I wouldn't run anything hotter than 100°C. Besides tubes that is
Tim
Heat
Hi
I have a Krell KSA200s which I leave permanently on. During normal days it just about reaches body temprature but on one exceptionally hot summers day I arrived home with the amp cooking. Not burning hot to touch but hot enough for serious concern. I shudder to think how hot it was inside or even worse to come home and find a hifi system meltdown but wonders above wonders no damage was sustained.
Joz
Hi
I have a Krell KSA200s which I leave permanently on. During normal days it just about reaches body temprature but on one exceptionally hot summers day I arrived home with the amp cooking. Not burning hot to touch but hot enough for serious concern. I shudder to think how hot it was inside or even worse to come home and find a hifi system meltdown but wonders above wonders no damage was sustained.
Joz
Re: Is not common 45 degrees in Brazil
I meant indoors, as in inside your house I read your posts, so Im allready relatively well informed about Brazil
In the summertime it will get up around 30C here (outdoors) as well, but thats noon peak temp. Indoors we frequently (as in a couple of days a year) see 40C in appartments and the like.
Magura
destroyer X said:
I meant indoors, as in inside your house
I read your posts, so Im allready relatively well informed about Brazil In the summertime it will get up around 30C here (outdoors) as well, but thats noon peak temp. Indoors we frequently (as in a couple of days a year) see 40C in appartments and the like.
Magura
SkinnyBoy said: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..
the oC/W ratings for a heat sink aren't linear -- you can do some calculating with the Thermalloy interactive tool:
http://www.aavidthermalloy.com/technical/thermal.shtml
my advice -- add a small fan -- and you can make a nifty controller with a thermistor and an LM3524 or LM3525 if you want to add bells and whistles.
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