Conrad Johnson PV12 AL

Hopefully hifiman5 will weigh in here as he has one that was modified and he is quite happy with it.  Good luck.  Regards......

I have had my PV12L extensively modified by Bob Backert of RHB Dezigns.  He focused on the power supply section of the line stage, bypassed the circuit board  traces with gold coated silver wire and added bypass boards to improve the performance. It is still a cj at heart but is more open sounding with a tighter more responsive bass response.

The PV12 used a 3 stage power supply. A pre-regulator fed a separate regulator for each side.

In addition to putting in better caps, or bypassing existing, adding some heat sinks to the regulators (really just transistors) could be useful in increasing reliability.

Also the resistor used in the power supply CRC circuits could be improved.

I’m really not a fan of mixed-metal conductors though.

Best bang for the buck on those is really the output caps though. They make much better caps than the PV10/12s had. If you are a noob, start there. :) Watch the cap voltage ratings carefully though.

Best of listening!

Erik

I want to thank Carmenc, Hifiman, and Erik for responding. I know capacitors have vastly improved since the first PV12, and that's why I'm looking into these modifications. I have a schematic of the PV12, and it looks like the diodes could stand an upgrade as well since there are some faster diodes; Shotsky or something like that is the name, that are used by Musical Design.

"Musical Design"; is close to me, and they do a lot of mods. If they are still in business I'll give them a ring. I plan to rebuild the PV12 if I ever get one. It's incredible how much improvement you can get if you're a technician, and can do good soldering work. The biggest problem I've ran into is finding room for those huge new caps, that I use to replace the electrolytic capacitors.

Once you find an old amp with a good design, it's simply a matter of finding enough room for new parts.


Enjoy the music.

Yes, you may very well need to stand them up.  Depends which direction you go. :)

Plan on standing them up and adding an extension.  So, a little soldering, and maybe a little heat shrink, with some solid copper core.  Also will need a dab of hot glue. Don't go nuts, in case you want to change things later.

Honestly, having done this before, I would encourage you to just do the output caps and stop there. :) After that it's a lot of diminishing returns, but those two caps can really do a lot.

Best,


Erik