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Old 13th August 2002, 01:47 PM   #1
saurus is offline saurus  United States
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Default P3A Power Supply

Hello all,

This is my first post, although I have been lurking for some time. I am preparing to build my first amp (a P3A) and I have this question:

I think I want to use separate rectifier/smoothing cap circuits for each of the two channels, but I notice that the power rails for the two individual amps on the P3A board are connected together. Doesn't this defeat the purpose of separate power circuits? Does anyone recommend cutting the board in half, or is this not a significant issue?
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Old 13th August 2002, 02:09 PM   #2
JBL is offline JBL  Canada
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I really don't think that this will be a problem.

This will not affect chanel separation at all.
Jonathan Blanchard (J.Bl.)
---Nothing is impossible---
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Old 13th August 2002, 02:22 PM   #3
tiroth is offline tiroth  United States
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I cut my boards in half. This also makes spacing the channels on a heatsink easier.
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Old 13th August 2002, 04:56 PM   #4
JoeBob is offline JoeBob  Canada
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If the + and - rails of the two channels are conected together on the PCB then it would be a waste to use two power suplies, afterall they'll be connected together as one after. You could cut the board or break the traces if you really wanted a dual-mono configuration. Or just make one psu for the board to run off of. From what people say the p3a seems like a top notch (I'm planning on building one for my sub) AB amp, so you would probably notice an improvement with the dual-mono setup (especially if you use bigger toroids).
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Old 13th August 2002, 07:24 PM   #5
paulb is offline paulb  Canada
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Cut the traces. You don't need to cut the board (although you could if it makes your internal layout easier).
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Old 14th August 2002, 01:35 PM   #6
saurus is offline saurus  United States
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Default I'll cut the traces.

Thanks, everybody!
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Old 27th August 2002, 10:01 PM   #7
annex666 is offline annex666  England
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I'm currently making an amp based on two P3A boards - one is used for each channel.

Each P3A is split so that they are driven from the same pre-amp signal but the output is connected in a passive bi-wire arrangement to the high and low frequency connectors of my speakers.

My question is how would I earth this amp? The power is by means of two toroids (one for each channel) each having a bridge rectifier and two 4,700uF caps.

Would I lose any of the benefits of dual supplies if I tie the earths together? Also I'm employing a zero-volt-line (see ESP) does this effect how the earth is connected?

Any help would be greatly appreciated.
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