Conrad Johnson PV-10A mod experiences?

I'd hazard a guess that a PV-10B would be a better platform to start with.

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.
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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.

Being a DIY'er at heart I've gone ahead and made some changes which have been highly successful.

1> for the line stage section, I have replaced the white CJ design bypass capacitors with like value Multicaps. I choose these because their physics makes sense, prior success with an Adcom DAC and relatively low cost (~$15 per capacitor). This immediately resolved the high frequency rolloff and some of the compression I was hearing.

2> I replaced the power cord in (typical lampwire)with a Furutech IEC socket. When i cut this cord it was heavily oxidized. This stage require care not to damage the transformer, make sure you place a solid obstacle buffer between the transformer and the work area where the metal must be cut to insert the IEC socket. total cost about $15 for socket. Significant improvement in base and dynamics if you use a quality power cord.

3> I replaced the 5 legacy tube sockets (bakelite?) with hybrid teflon, gold plated sockets, each ~$6 or total of $30. easy soldering replacement if you have a desoldering tool. This helped soldify, tame "wooliness" in the base and eliminated edginess in the highs.

Solder used throughout, Cardas.

ecstatic to have my preamp sounding great again.

Still waiting on delivery of the Multicaps for phono stage but I have no doubts they will wipe out the slowmess which still remains in phono transients. Only annoyance here is that 0.15uf 400 VDC wasn't available, per other upgraders advice i've ordered 0.22 uf values.

Total cost to bring a PV10-A back to 1993 newness for line stage around $75 + soldering tools. Will post outcome later this week for phono stage.

phono stage is proving a little more tricky. The Multicaps indeed wiped out the transient issues. But they sound "edgy", irritating in the phono stage. Mulling over other choices for the bypass capacitors