Electronics > Beginners
Class A Amplifier Heat Sink Requirements!?
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Gyro:
^ What they said.

I don't think it's possible for the voltage between the +Ve and -Ve rails to be as low as 40V  :-\. 40W RMS is a pretty high output goal for a class A amp and couldn't be achieved by the figures you mentioned. Even modest Class A amps, like the Linsley-Hood, dump an awful lot of heat, as Benta mentioned.

Maybe you could post the schematic?
soldar:

--- Quote from: Robbie010 on March 14, 2019, 12:29:17 pm --- This is my first DIY build, the amp is actually a Nelson Pass A40 design.
--- End quote ---
I believe that is not a Class A but a complimentary pair class B amplifier.
Benta:

--- Quote from: soldar on March 14, 2019, 06:35:30 pm ---
--- Quote from: Robbie010 on March 14, 2019, 12:29:17 pm --- This is my first DIY build, the amp is actually a Nelson Pass A40 design.
--- End quote ---

I believe that is not a Class A but a complimentary pair class B amplifier.

--- End quote ---

The Nelson Pass A40 is indeed a class A design, and from pictures it has enormous "cooling towers" with fans:

Gyro:
It's a shame 2SK170s and 2SJ74s are unobtainable these days, you could get away without heatsinks at all  :) ...

The Nelson Pass 'Beast with Two Thousand Three Hundred and Fifty Two JFETS': http://www.firstwatt.com/pdf/art_beast.pdf
Benta:

--- Quote from: Gyro on March 14, 2019, 07:50:03 pm ---It's a shame 2SK170s and 2SJ74s are unobtainable these days, you could get away without heatsinks at all  :) ...

The Nelson Pass 'Beast with Two Thousand Three Hundred and Fifty Two JFETS': http://www.firstwatt.com/pdf/art_beast.pdf

--- End quote ---

That's one of the craziest designs I've seen. But the measurement results are impressive.

2SK170 and 2SJ74 are indeed available today from Linear Systems as LSK170 and LSJ74.

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