P3A layout

bracoraab · 29th July 2009, 12:29 AM

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
Braco

EchoWars · 29th July 2009, 03:13 AM

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

sakis · 29th July 2009, 06:07 AM

---- 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 ...

RESULT

*****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 ...

TIP
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 ......

sakis · 29th July 2009, 06:35 AM

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:
I´ll go for some modifications you propose and will post again.
Tx.
Braco
Sorry my English!

bracoraab · 31st July 2009, 02:27 PM

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

29th July 2009, 06:07 AM	#3
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	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 ... RESULT ***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 ... TIP 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 ...... __________________ SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

29th July 2009, 06:35 AM	#4
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	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 __________________ SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

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29th July 2009, 03:13 AM	#2
EchoWars diyAudio Member Join Date: Dec 2002 Location: Left of the Dial	It's certainly compact. Looks like you could fit it in a watch case.

29th July 2009, 02:02 PM	#5
bracoraab diyAudio Member Join Date: Sep 2004 Location: under the boardwalk	Hi Sakis: I´ll go for some modifications you propose and will post again. Tx. Braco Sorry my English!