2. amps-preamps
  3. 1297052009

Conrad Johnson PV-10A mod experiences?

Has anyone had experience performing a mod on the CJ PV-10A? I'm fond of this preamp, it has that wonderful tube openness and sweetness for harmonics. However over the past 6 months as I've delved into PC audio and DAC improvements, I've come to realize two things about it

1) its slow on transients
2) its dynamically compressed.

I'm using Mullard NOS tubes throughout as these seem wonderfully detailed with excellent base.

Since the preamp is built like an engineering prototype (overbuilt)my gut hunch is that some caps have aged (circa 1993)and need replacement, specifically the white CJ caps
and am thinking about replacing them first with Multicaps.

Wondering if anyone has experience trying to revitalize a PV 10A?
128x128davide256
usblues
1,217 posts
 
I also have heard good things about RHB Designs.That being said I would be hesitant to mod a PV 10,YMMV,Bob
davide256's avatar
davide256 OP
399 posts
 
Mod might be too strong a word. Rejuvenate is probably better, For example in the main pre section there are (2) 2uf 450vdc capacitors that have an ARC label and which show end swelling. So likely these need a quality replacement. Interestingly enough, CJ doesn't list the PV10 as having a teflon replacement capacitor option like many of their other older preamps. At the same time power supply design has improved in the last 20 years so opportunities exist to eke better transients and base out of an older design
unsound
7,329 posts
 
I'd hazard a guess that a PV-10B would be a better platform to start with.
jeffreybehr's avatar
jeffreybehr
805 posts
 
First, e-mail c-j... service@conradjohnson.com ...and ask for a copy of the schematic for your unit.

I imagine the reason c-j doesn't offer a Teflon-cap upgrade for this preamps is twofold--the caps are BIG and probably there's not enough space for them, and the caps are EXPENSIVE, retailing for maybe more than the used value of the preamp.

But that doesn't mean one can't make it better, so get that schematic.
.
hifigeek1
770 posts
 
Davide, you can talk to Ed at C/J customer service. He is a super nice guy. They probably have mods for that unit. Replacing coupling caps is probably a good idea especially if you are seeing swelling end caps or the caps are not blocking DC voltage. Odd a cap would say ARC on it as that sounds like an old Audio Research part. Maybe this was a prototype...Since coupling caps are like speaker wire and interconnects in that they act like tone controls, it's a rather subjective thing. I was never a big fan of the old m.i.t. caps but again it's just my personal experiences with them.
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