Rod Elliott P3A with SANKEN 2SC2922/2SA1916

Project16 · 19th January 2013, 04:40 PM

Hello all!

With a few pairs of Sanken, I decided to make a card for the P3A class A.
I do not know if the design of the circuit is optimized properly but I have found no connection error.
For those interested I have attached the files.

Greetings!

amptech · 21st January 2013, 06:40 PM

hi, in this design one of the driver transistors is used to monitor the q-temp.. your lay out does not show where you've placed the tracking transistor..

Ian Finch · 21st January 2013, 10:52 PM

You are pushing the stability envelope using very high Ft output parts in a CFP ouput stage.
That's risky but to compound this with long, wandering traces of inappropriate and strangely
varying thickness there is asking for trouble. You can do a lot better there in the physical location
of the drivers and placing the output transistors along the same edge to get the traces to more
reasonable length. Lead stress due to mechanical assembly issues will likely be reduced too.

There are several threads here of guys DIYing their own P3a PCB which is fine as a learning exercise,
so please search those P3a threads for the hard lessons and good advice in PCB layout first.
This topic comes up again and again so it's not just a matter of one opinion.

Project16 · 03:10 PM

I changed the design in the hope that here will be better. The drivers are now two transistors coupled to the transistor by a thermometer aluminum plate serving as a heat sink.

Thank you for your contributions!

Project16 · 29th January 2013, 12:49 PM

Hello all!

I tried to improve the design of the card, but I have a small question.

The first image track passes between the legs of the transistor Q8 but I think it is very close.

On the second picture I put a strap.

What is the best design?

Thank you!

jaycee · 29th January 2013, 03:16 PM

The second one, if you are making the PCB at home and have no soldermask.

Q9 should not be a TO-220 device... an MJE340 (TO-126) will be OK though.

In this design, and especially with those Sankens, i would recommend extra 330uF decoupling capacitors in parallel to C+ and C- for stability.

Project16 · 29th January 2013, 04:10 PM

Jaycee thank you for that answer.

Q4, Q5, Q6 and Q9 are TO 126 (BD 140, 139), I was not in my software footprint for those below.
After checking my drawing has a small error that I repaired.

Thank you again!

21st January 2013, 10:52 PM	#3
Ian Finch diyAudio Member Join Date: Apr 2010 Location: Coffs Harbour, on the east coast	You are pushing the stability envelope using very high Ft output parts in a CFP ouput stage. That's risky but to compound this with long, wandering traces of inappropriate and strangely varying thickness there is asking for trouble. You can do a lot better there in the physical location of the drivers and placing the output transistors along the same edge to get the traces to more reasonable length. Lead stress due to mechanical assembly issues will likely be reduced too. There are several threads here of guys DIYing their own P3a PCB which is fine as a learning exercise, so please search those P3a threads for the hard lessons and good advice in PCB layout first. This topic comes up again and again so it's not just a matter of one opinion. __________________ regards

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21st January 2013, 06:40 PM	#2
amptech diyAudio Member Join Date: Jan 2009 Location: Glasgow	hi, in this design one of the driver transistors is used to monitor the q-temp.. your lay out does not show where you've placed the tracking transistor..

29th January 2013, 03:16 PM	#6
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	The second one, if you are making the PCB at home and have no soldermask. Q9 should not be a TO-220 device... an MJE340 (TO-126) will be OK though. In this design, and especially with those Sankens, i would recommend extra 330uF decoupling capacitors in parallel to C+ and C- for stability.

29th January 2013, 04:10 PM	#7
Project16 diyAudio Member Join Date: Nov 2012	Jaycee thank you for that answer. Q4, Q5, Q6 and Q9 are TO 126 (BD 140, 139), I was not in my software footprint for those below. After checking my drawing has a small error that I repaired. Thank you again!