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Old 15th February 2011, 08:39 PM   #1
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Default ESP P3A

My own take on a layout for Rod Elliots P3A amplifier.

60-80W Power Amplifier

With heatsinks for the drivers transistors, 470uF supply caps on each rail, close to the output transistors. Used MJ15003/MJ15004 NPN/PNP TO-3 transistors for output.

Board is made somewhat long at 160 mm but only 80 mm wide. The extra length is for more spacing between output transistors which should lead to better utilization of the heatsink.

Board is singlesided for easy prototyping and because I can.
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Old 15th February 2011, 09:53 PM   #2
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Is pin26240 supposed to be the speaker ground? if so, it seems to be floating...
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Old 15th February 2011, 10:42 PM   #3
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Join all spare copper to ground.
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Old 16th February 2011, 06:07 AM   #4
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Quote:
Originally Posted by pinkmouse View Post
Is pin26240 supposed to be the speaker ground? if so, it seems to be floating...
Speaker ground will be at the star ground.

I have +V pin, -V pin, input pin, 2 x input gnd pin of which one should go to the star gnd point, output pin, Zobel gnd pin.

But I might be seperating +V and -V gnd from signal gnd so I get separate supply gnd.

Last edited by Neutrality; 16th February 2011 at 06:32 AM.
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Old 16th February 2011, 06:17 AM   #5
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Originally Posted by nigelwright7557 View Post
Join all spare copper to ground.
Why? That seems to go against what everyone else here usually advocates.

Last edited by Neutrality; 16th February 2011 at 06:29 AM.
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Old 16th February 2011, 07:47 AM   #6
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Forgot to mention that the input cap, which is a 4.7 uF electrolyte in the original ESP schematic, has been changed to a 4.7uF film cap instead. Going to use a Evox Rifa MMK 4.7 uF, 63V cap. But theres room for other options as well.

Last edited by Neutrality; 16th February 2011 at 07:50 AM.
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Old 16th February 2011, 09:10 AM   #7
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Hi there neutrality a good pcb layout apart from the proximity of the input cap and the output node should be as far apart as possible.Hope you dont mind me pointing this out. Btw i have made my own pcbs for this design
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Old 16th February 2011, 09:39 AM   #8
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Originally Posted by p robertson View Post
Hi there neutrality a good pcb layout apart from the proximity of the input cap and the output node should be as far apart as possible.Hope you dont mind me pointing this out. Btw i have made my own pcbs for this design
Dont mind that at all, and a good observation.

Funny, I know they should be apart but somehow didnt think about it when doing the layout.

Thats something Ill look at later today, as well as the separation of input gnd from the other grounds.
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Old 16th February 2011, 10:05 AM   #9
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P3A Take Two.

Input cap moved from output, separate gnd for +V and -V supply.
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Old 16th February 2011, 10:58 AM   #10
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I would make Q9 (bias) a TO126 and move its location to mount onto Q5's (driver) heatsink to thermally track, as obligatory for a cfp O/P stage.

Brian.
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