What size heatsink is needed for Rod's 3A amp?

kec · 21st February 2002, 06:21 PM

I'm interested in Rod's 3A project. What's a good heatsink for it? How big should it be?

For anyone that has one, does it run real hot?

Thanks,
Ken

ih · 22nd February 2002, 09:51 AM

Fairly big, but not excessively so. Rod recommends a 1deg/C heatsink - I used a 0.7deg/C heatsink with TO-3 outputs, and cut a hole in the back of my case so it could mount on the outside.

In hindsight, that's overkill - I could've used a smaller one, and mounted it inside the case. It gets warm, but doesn't heat up much more even running hard.

paulb · 22nd February 2002, 04:22 PM

This amp is quite flexible in regards to power supply voltage and load, and the heatsink requirements will vary accordingly. I'm using a +/-25 VDC supply and am driving a 4-ohm load. It sounds like my heatsinks are about the same as ih's, and I mounted them on the outside as well. They barely get warm to the touch, but I don't run at significant power very often.
Later, I'll change to a +/-42VDC supply to run an 8-ohm speaker. My feeling was that this higher voltage was a bit too much for driving 4 ohms.
I'm very happy with this amp. I'd go with the biggest heatsinks that are reasonable for your budget and the case you select; reliability will increase if you keep the temperature down.

hugobross · 25th February 2002, 08:08 PM

Dear kec,

I agree with PaulB:

"I'd go with the biggest heatsinks that are reasonable for your budget and the case you select; reliability will increase if you keep the temperature down."

If your heatsinks seems to be too small you can always add a fan

Best regards,

HB

blmn · 26th February 2002, 12:59 AM

Just to add something to Hugo's statement, maybe some thermal sensor to start the fan just when the heatsink achieve, for example 40-50 Celsius degrees, to avoid the fan's noise.

regards

Lisandro_P · 26th February 2002, 01:13 AM

I beleive Rod stated in the article that a 0.6 °C/W would work good for an stereo pair. I once found that kind of sinks for $20-25; if you get those prices, buying one for each would be a bit overkill, but if you have the $50 the amps would run really cool.

A friend of mine used a 1°C/W on his and the amp runned just warm.

21st February 2002, 06:21 PM	#1
kec diyAudio Member Join Date: Mar 2001 Location: California	What size heatsink is needed for Rod's 3A amp? I'm interested in Rod's 3A project. What's a good heatsink for it? How big should it be? For anyone that has one, does it run real hot? Thanks, Ken

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22nd February 2002, 09:51 AM	#2
ih diyAudio Member Join Date: Dec 2001 Location: Sydney, Australia	Fairly big, but not excessively so. Rod recommends a 1deg/C heatsink - I used a 0.7deg/C heatsink with TO-3 outputs, and cut a hole in the back of my case so it could mount on the outside. In hindsight, that's overkill - I could've used a smaller one, and mounted it inside the case. It gets warm, but doesn't heat up much more even running hard.

22nd February 2002, 04:22 PM	#3
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	This amp is quite flexible in regards to power supply voltage and load, and the heatsink requirements will vary accordingly. I'm using a +/-25 VDC supply and am driving a 4-ohm load. It sounds like my heatsinks are about the same as ih's, and I mounted them on the outside as well. They barely get warm to the touch, but I don't run at significant power very often. Later, I'll change to a +/-42VDC supply to run an 8-ohm speaker. My feeling was that this higher voltage was a bit too much for driving 4 ohms. I'm very happy with this amp. I'd go with the biggest heatsinks that are reasonable for your budget and the case you select; reliability will increase if you keep the temperature down.

25th February 2002, 08:08 PM	#4
hugobross diyAudio Member Join Date: Jun 2001 Location: Flanders, Belgium	Dear kec, I agree with PaulB: "I'd go with the biggest heatsinks that are reasonable for your budget and the case you select; reliability will increase if you keep the temperature down." If your heatsinks seems to be too small you can always add a fan Best regards, HB

26th February 2002, 12:59 AM	#5
blmn diyAudio Member Join Date: Feb 2001 Location: .	Just to add something to Hugo's statement, maybe some thermal sensor to start the fan just when the heatsink achieve, for example 40-50 Celsius degrees, to avoid the fan's noise. regards

26th February 2002, 01:13 AM	#6
Lisandro_P diyAudio Member Join Date: Oct 2000 Location: Argentina	I beleive Rod stated in the article that a 0.6 °C/W would work good for an stereo pair. I once found that kind of sinks for $20-25; if you get those prices, buying one for each would be a bit overkill, but if you have the $50 the amps would run really cool. A friend of mine used a 1°C/W on his and the amp runned just warm.