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bracoraab 29th July 2009 12:29 AM

P3A layout
2 Attachment(s)
Due Rod not allow to publish in his forum pics of pcb's ( 100% reasonable) I'll like to know what do you diyers think about this layout.
The 5w resistors R13 and R14 and the 100n decoupling caps go under the board.
PS connectors are fast-on.
Tx in advance

EchoWars 29th July 2009 03:13 AM

It's certainly compact. Looks like you could fit it in a watch case. ;)

east electronics 29th July 2009 06:07 AM

just a few things
---- the size of the speaker out trace doesnt need to be that big
---- square traces generally causes complications
---- Q7 will work better if located very close to ltp stage
---- Miller caps located next to vas and n driver will need to be just a bit biger if it is a silver mica or so is to be used ( ceramics there will not do the job )

-----P3A will work a lot better with better transistors tip series will play bellow average

-----If the amp will be used more than casual listening and abuse is an option you might need to relocate vbe multiplier very close to any of the drivers so it can sense temperature from there and this will improove the safety aspect of your amp

----there is no zobel in the circuit ....if you have in mind to relocate it on the binding post / output of the amplifier ....that is a nice idea but keep in mind that seperated trace retutrn to ground will do miracles there

---- 100mfd /63 V caps located left and right on the board will also requiere 100nf bypass .... all this will work better as close is possible to the output transistors

----After the above you need to have trace ground as small is possible ....this W you formated for ground is not the best thing and if you relocate bypass and decoupling very close to outputs then the ground trace will become even bigger .....dead end ...


*****to be able to fullfill all the above specs i think that it cannot be done in a single layer pcb

***** Question is : does the P3A amplifier worth all this ???? presumably not it is my favourite amp of all times and i would do i think like that as personal project for my own plesure .....but truth remains that if you invest in an advanced and sophisticated pcb you may as well construct a more sophisticated amplifier ...

in my boards and my pcb design i noticed that to my taste works a lot better to have the psu caps on board ( but that is me this is the way i like to do things ) and YES this amplifier is pcb sensitive ......

east electronics 29th July 2009 06:35 AM

by the way
i dont mean to terorize you ....

your pcb will play happily as is

this is what it takes to make the amp really perfect ....

best regards sakis

bracoraab 29th July 2009 02:02 PM

Hi Sakis:
IŽll go for some modifications you propose and will post again.
Sorry my English!

bracoraab 31st July 2009 02:27 PM

2 Attachment(s)
Hi, here some modifications
blue elements go undet the board:5w resistors, 100n bypass caps & zobel network.
I canŽt do miracles with ground, I have no experiences with doble layer boards.
IŽll try this project to triamp my system, for the mids and highs (recommendations please!)

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