P3A build .. simple designs can sound excellent

[Kannan_madhu]

P3A is a well-regarded Amplifier among DIY audio enthusiasts with very simple schematics. It can be built with commonly available components nothing exotic is needed. Output is cfp or Sziklai pair , and according to many DIY people this sound faster and have smooth highs . P3A outputs 60w power into 8 ohm loads which is sufficient for home listening . All details of this amp can be found in ESP website PCBs are also available there . since i make my own pcbs i made a similar design in my favorite program Easyeda .

 

[Kannan_madhu]

Build Finished and heavy DC offset ..

 

[yogibear]

View attachment 85064

Build Finished and heavy DC offset ..

Did you measure each component for value ?

 

[hydrovac]

View attachment 85064

Build Finished and heavy DC offset ..

What is the DC offset reading?
I read on https://sound-au.com/project3a.htm
"Verify that the DC voltage at the speaker terminal does not exceed 100mV, and perform another 'heat test' on all transistors and resistors."

...

 

[Kannan_madhu]

One leg of the driver had a dry solder and that wasted many hours of mine I thought I did some mistake in routing.
Everything worked fine after resoldering it. DC was less than 30mv after that.
This amp lives up to the reputation very good sound quality from such a simple circuit.

I powered it with a 25 0 25 v 5 A transformer and got around 60w it may give slightly higher with this PS but my inbuilt signal gen has a limited output. since it was stable I built its pair also

 

[Kannan_madhu]

Here is a video of the build

wattage

 

[availlyrics]

Great build!
I'm also planning (since long time) to build it on a home-brewn PCB , will definitely ask for your advice.
BTW any ideas about getting those driver stage transistors( genuine) in retail qty

 

[Kannan_madhu]

Great build!
I'm also planning (since long time) to build it on a home-brewn PCB , will definitely ask for your advice.
BTW any ideas about getting those driver stage transistors( genuine) in retail qty

You can get CDIL make ,to my knowledge there are no fakes of CDIL. I buy from etstore.in

 

[keith_correa]

What is the bias set at?

 

[Kannan_madhu]

What is the bias set at?

30mA

 

[Kannan_madhu]

Designed a powersupply board for this . With additional supply for tone control/ pre and MP3 usb module

 

[Kannan_madhu]

View attachment 85124
Designed a powersupply board for this . With additional supply for tone control/ pre and MP3 usb module

 

[availlyrics]

I got all the parts ready, CDIL BD139/140, Philips BC546B, MJL21193/94.

1. Do I need to check hfe of each CDIL BD139/140, Philips BC546B for better matching? In that case which transistors are more critical?

2. Can I use A1106. C2581 (Vcbo = 200 V, Vceo = 140 V , Vebo = 6 V , Ic = 10 A , Pc = 100 W) in the output stage, instead of MJL21193/94 in my next build?

3. Can I use lower supply voltages like +/- 30V or even lower? In such case , can I connect 2Ohms speakers or difficult to drive 4 Ohms speakers with impedance dip upto 2.5 Ohms? (Lower Output power is not an issue). I have read on ESP site that in Class A mode it can run on +/-20V, but my plans are to run it in Class AB only but at +/-20V or do I also have to make some changes in passive components values( I'm ok with +/-25V also if its too tricky) ?

4. One more noob question, how do I use your P3A layout for toner transfer method, which requires a .pdf file

Thanks

 

[Kannan_madhu]

I got all the parts ready, CDIL BD139/140, Philips BC546B, MJL21193/94.

1. Do I need to check hfe of each CDIL BD139/140, Philips BC546B for better matching? In that case which transistors are more critical?

2. Can I use A1106. C2581 (Vcbo = 200 V, Vceo = 140 V , Vebo = 6 V , Ic = 10 A , Pc = 100 W) in the output stage, instead of MJL21193/94 in my next build?

3. Can I use lower supply voltages like +/- 30V or even lower? In such case , can I connect 2Ohms speakers or difficult to drive 4 Ohms speakers with impedance dip upto 2.5 Ohms? (Lower Output power is not an issue). I have read on ESP site that in Class A mode it can run on +/-20V, but my plans are to run it in Class AB only but at +/-20V or do I also have to make some changes in passive components values( I'm ok with +/-25V also if its too tricky) ?

4. One more noob question, how do I use your P3A layout for toner transfer method, which requires a .pdf file

Thanks

i will send you the pdf you can use toner transfer method ( check youtube for more details about heat transfer PCB making ) or if you want a PCB I can send that too