ESP P3A Mods/Upgrades

[blap0220]

Hello all!

I've finished building my P3A amp and it sounds good, but a little harsh. I know it's a popular amp, so I'm fishing for any mods or upgrades people have done on theirs. Please list any and the results of the mods. Really interested in knowing whether or not I can get a warmer sound out of it.

My P3A:
Power Supply using dual rectification and 12000uF cap banks for the 42V +/- rails.
Solen coupling capacitor.
Mica miller caps.
Metal film resistors.
MJE15034/MJE15035 driver trans
MJL4302/MJL4281 output trans

Thanks!

[MJL21193]

Hi,
Did you use Rod's circuit boards?

[blap0220]

Originally posted by MJL21193
Hi,
Did you use Rod's circuit boards?

Yep. I used his boards.

[MEGA-amp]

1200uF

How many are you using per rail? I would definitely increase this.

[blap0220]

Originally posted by MEGA-amp


How many are you using per rail? I would definitely increase this.

oops!! typo. I meant 12000uF per rail. 4 caps per rail

[MJL21193]

Originally posted by blap0220

Power Supply using dual rectification and 1200uF cap banks for the 42V +/- rails.

How much capacitance do you have in the PS? Not just 1200/rail?

A while ago I simulated this amp and the results were less than impressive. But hey, it's only a sim, not real life.

Which did you use for Q4 - MJE15035 or BD140? For what it's worth, the BD140 simmed with lower distortion.

[rabbitz]

Been playing with the P3A for about 4 years on and off and this is the best sounding version I've found which is quite a leap on the others I've tried. The amp is actually quite involving to listen to.

Changed to the 2SC5200 2SA1943 combo, C4, C6 to silver mica, C5 to Nichicon FG, C3 to Hitano EXR. The input cap C1 was where I got a large surprise. Started with 2.2uF Auricap (sounded confused, rolled off each end and lost top end sparkle), then Vishay 1uF MKT (better focus, good top end but bass lacking) and then 10uF Nichicon ES (22uF also worked well) and it all snapped into place. Additional bass and punch, better separation and depth.

100uF caps added on the PCB where the by-pass caps are and those are placed under the PCB..... makes a good difference with the amp more punchy, lively, good transient control and speed, allowing nuances through and throwing the vocals etc out of the mix. There is now depth appearing and the soundstage sounds better.

Power supply was a DX supply by Carlos (aka destroyer x) using 4 x 4700uF Nichicon KG (Gold Tune). This power supply gave it a nice lift and better than the supply just with 4 caps. Uses a single 300VA 25-0-25 for 35V rails.

All the values are standard and I've heard there could be benefits removing or reducing R1, R3.... increasing R2... reducing C4, C6 as the 100pF could be killing the sonics. None of these have been tried and are not my suggestions as they are only what I've read and heard.

[rabbitz]

... and one on a later PCB which is not split.

[blap0220]

Wow. that's some good info. I'll try some of those.
Do you know if replacing the C2 capacitor with something better than ceramic down to 100pF would help? I have a WIMA 100pF polypropylene cap lying around.

Thanks!

[rabbitz]

I think C2 is best left at 220pF and I left it as a ceramic but I'm sure you could use a silver mica or polystyrene. This is based on what I've seen in other amps such as the Dx as I'm a builder and tweaker.... not amp designer.

You could always ask on the ESP forum.