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?
I was just reseaching the PV-10A a few days ago, and it really was made in three different version, but CJ did not give it a new name or MK# etc.

I was considering buying one, so it would be interesting to know what options there are. On the other hand, I wonder if the money would be better put on a new preamp that is close in price, like CJ's "Classic" preamp. I wonder what the sound improvement would be over a 25+/- year old preamp if any? Does "Classic" transulate to "same ol-same ol"?
I believe the 10A differences are all centered around the balance control knob which was eliminated in the last version. There is also a 10AL which had no phono section. The classic version front panel looks like a PV-10A but its tube complement is different and includes circuit components derived from the PV-12. As to sound on a classic, its a newer tube CJ... how can it not be be improved?
I've not listened to earlier models, but I really love my PV-15.
I had my PV-12L extensively modified by RHB Dezigns located in Churchville, PA. Proprietor, Bob Backert designs his own proprietary circuits for the gear he modifies. He loves to work on cj gear! You can talk to him, discuss your sonic goals for your cj and he'll be able to tell you what he can do to get you there.

If you check other threads that discuss Bob's work you will find nothing but accolades! He is the real deal and a true gentleman to boot.

If modifications are in your future please consider giving Bob a call.
I also have heard good things about RHB Designs.That being said I would be hesitant to mod a PV 10,YMMV,Bob
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
I'd hazard a guess that a PV-10B would be a better platform to start with.
First, e-mail c-j... ...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.
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
I have found Multicaps to have an upper midrange glare. I remove them when possible. I also never mix coupling caps.
Hi Davide256,breakin time perhaps?Cheers,B
I used Black Gate caps when they were available to replace the lytics. Someone told me Jentsen work well. The tubes you're using are good. I'm sure the sound will tighten up if you replace the electrolytics. I use RCA NOS 12 au7 cleartop, mullards are probably better.
WHICH MultiCaps???????????????????????? There are several versions.

The RTXs, 'styrenes, are VERY-good-sounding caps and do indeed require a hundred or 2 hours to break-in and sound their best. The metalized PPMFXs are entry-level-hi-end caps, ones I'd never use unless low cost were the primary goal, and then I still wouldn't use them, I'd use SoniCap gen.1s. I think the PPMFXs, if that's what you used, will sound a bit edgy forever.
looks like its the usual with audio, fix 1 problem only to reveal another. I've known for a while that I need to send my Sota back for a new bearing but with the old caps the problem hadn't been "glaring". I've swapped in my backup AR ES turntable and the problem is gone albeit nowhere near as silky in sound as the Sota. As to caps used they are the RTX Multicaps. so will let this ride for 100 hrs or so of play and see what happens. I do have to admit the VCAPs (teflon/w tin foil)have my curiosity piqued, but that would run about $330 for the 4 required bypass caps vs the $50 for the Multicaps I paid.
Those white capacitors you are referring to are teflon capacitors, they last indefinitely; it's the two electrolytic capacitors that need changing. Find the best capacitors of the same value and replace them
Just getting back to this thread after a while. The small white caps in the PV-10A were
definitely toast. As to being teflon, thats speculative. From the era the PV-10A was made in
they might have been Wonder caps or they could have been rebadged Rel caps
based on materials construction.
After break in the RTX Multicap replacements had solved much of the dynamic range issues but the high frequencies were still soggy (splat, not snap). Both the mains and phono section have a pair of 2uf capacitors in their output stage. I decided on the mains to replace those first with Solens polypropylene and tinfoil caps, 2uf / 400VDC, SE Series. These I installed last night and they immediately made a big difference in high frequency range
and crispness of percussion transients. Still not getting quite the low base response I can
get by going DAC direct to amp but above 40hz all appears right now. Will let this bake
another 30 days and update
David, if you're talking about the low frequencies of music, it's bass, not base.

Very happy so far with the Solen replacements in the pre main section. While the pre is not as fast as going DAC direct for transients, the preamp now comes quite close and cause more smiles :<). Played a few LP's last night, I can definitely hear some of the same blurring on the phono side from the old 2uf caps so will pull the trigger this week on ordering Solen replacements for those. I do notice that the phono section is noisier than one would like, one of the original review critiques of the PV10A, still scratching my head on what can be done to improve that.
Hi there,
You will find the cheapest Multicaps are far quicker and more resolving than the Solens. I would suggest you try these instead. Search on this site for Carey caps for others experiences. Good luck.
Hi Davide,
I would recommend the Bob Backert power supply mod for your PV10A. I have it in my PV12. I am now getting it put into my Art Audio 'Vinyl One' phono preamp. It's like getting a whole new amp. I believe the cost was $900.
I fully agree with your first 2 comments about the PV10A:
1) it's slow on transients
2) it's dynamically compressed.
With the Backert power supply, speed and dynamics will increase very noticeably. The compression will mostly vanish. When I heard my "new" PV12 for the first time, I went nuts. Bass punch was incredible, way better than any preamp I've ever heard, tubed or solid state.

I have no financial interest in Mr. Backert's mods business. I am, however, going to team up with Mr. Backert and try to get audio companies interested in using his power supply. So, even though I won't benefit directly if you get this mod done, if you publicize your opinion of the results, I could benefit *OR* I could suffer, depending on what your publicized opinion is. Everybody I know who has gotten it so far has loved it to death.
Mr. Backert's company, RHB SoundDezign, is at 215-355-0529.
I've replaced the phono output caps as planned with the Solens. But in the mean time i've also upgraded my DAC. So once again the PV10A is doing some things well (tonal colors) but direct to amp from DAC is superior for fine detail and low bass. At this point I'm 90% certain im going to buy a Prima Luna product, either the prologue premium integrated or the Dialogue 2. Might be a sacrifice for bass wattage authority but the listen I had with just a Prologue 5 showed me that bass tonal color and weight is bleached in my current Pv10A/DH200 amplification.
After weighing pro's and con's I decided to go with the Prologue Premium integrated and bought separately cryo treated Genalux KT-88's (the EL34's just didn't cut it). The PV10A beats the Prologue for pre when feed thru the home theater inputs... more air, detail and extension into the top and bottom range of the audio spectrum. I'll probably tinker with upgraded components in the Prima Luna pre section later this year but in the meantime I've got 0.01uf bypass Vcap replacements on order to replace the Solens I installed in the CJ pre mains section... will check back in with a report in 60 days after the obligatory 100-200 break in hrs pass. Love the amp section for the prologue, no lack of power or base performance issues with the Magnepan 1.7's
I hadn't expected immediate improvement using the VCaps, noe the less I got one. While theres still a long break in time ahead, Im finding on every piece that has percussive bass there is much deeper bass. Bass drum is now a thunderous joy to listen to versus a polite whack.
did any of you replace the caps and resistors yourself.. if so how was it done..............thanks
resistors are all original. Output section of pre and phono has 2 2uf PPE Solens which I replaced some while ago
with the SE Solens series
also replaced the stock electrolytics on power supply section with Nichicon fine gold caps but that didn't seem to cause a noticeable change
ok so the upgrade bug is hard to stop. I've now upgraded in the pre mains section the 13.5 uf solens to 2x 6.8 uf Mundor Supremes and replaced the 10uf Solens with same in Mundorf Supreme. A wonderful improvement, gobs of tone color detail, accompanying players get the same clarity as the lead line. At first listen I was worried I'd just put in a high pass filter... no cymbal sheen. Now after 25 hours of play, all has evened out and Mundorf Supreme has my utmost respect for musicality at an affordable price.
When my PV-10 (that I had for 17 years)needed repair (a tube arced and blew it out), I sent it to Bill Thalmann at Music Technology. IN addition to the repairs, I had him do his mod package (which included replacing the original caps with "auricaps", among other changes). The pre did sound more accurate and "faster," but it may have lost some of the ambience and warmness that it had originally. Unfortunately, I don't know if it would have improved over time, because after a few months, the same thing happened again (probably my fault, I put in a tube I shouldn't have). Unfortunately, Bill never responded to my E-mails after that. I couldn't afford to have it fixed again, so I sold it as is, and went back to solid state (Emotiva, with a Yaqin CD-1 tube buffer). Personally, I was never happier with my CJ than when I had a Bugle Boy and an RCA triple mica black plate 5751 in the line, and Telefunkens in the phono. The mods made a difference, but I was always happy with the original sound of the PV-10. (great midrange and phono stage). I've always had a SS amp (Adcom, then Classe).
Just wanted to add that you would get Auricaps in your power supply with the Backert mod that I mentioned above.

Deleting the crappy electrolytics is one reason that it makes a preamp sound so incredible.

It's a bit over $700 for a CJ. The price varies with other kinds of preamps. Instead of the Auricaps, you can ask him to use V-Caps, and it's still only $900. But the Auricaps are already a HUGE upgrade compared to the stock electrolytics.

To my knowledge, there is no other power supply on earth that gives you teflon caps, like V-Caps. It just doesn't exist. I think this is why he is getting it patented.

Have continued to work on this as the board layout is easy to work with. Since last post I have taken out the 2uf Solens SE capacitors in the phono and pre sections because of "edginess" and replaced them with REL Theta's. In the phono section I have substituted Rel RT 0.1uf values (the original 0.15's have few quality manufacturer options). In the pre section I have swappped out a 13.5 Solens to 2x6.8uf Mundorf supremes, a 4.0uf Solens for a 3.9uf Mundorf Supreme, the power supply pair 20uf Solens for 20 uf Clarity TC series and replaced a 4700uf Electolytic
with a Mundorf MLGO.

Overall very pleased, none of the CJ character has been lost, just rejuvenated with greater transparency and extension in the highs. I plan over the next 90 days to take two additional steps before calling this done (1) the power supply diodes are original (slow), will replace with HiperFRED's (2) the phono section was remarked as not the quietest in the original product review, age hasn't changed this. There are a number of bare wire runs in the phono section and I'm suspicious of how close some of the cap terminal wires are to the tube socket contacts, will report if I find any steps that reduce the phono section noise.
since last post I have actually made 3 changes. (1) in general I prefer to stay within manufacturer specs and I was curious about the Obbligatos so I've swapped in a 0.15uf Obbligatto to replace the Rel RT 0.1uf. So far its nice, sweet sounding, no negative consequences. More to come after I get some burn in time on it. (2) replaced the slow GI 854 8818 diodes (ttr =200) with Hexfred TXYS 15A 1200V soft recovery diodes (ttr=40). A very pleasant change eliminating what before I thought was "digital hardness" in recordings. However all is not completely well in Mudville as the hard percussive sounds (block bell) have lost some authority and I'm suspicous that other transient areas are damped. So will be swapping these out for "BY228TR, Vishay 3.0A 1500V" sinter glass diodes next when they arrive... these have an even lower Time To Recover (ttr)than the other 2 and no soft recovery characteristics. Mean time I can enjoy listening at an extreme end of tube sweetness.

Now for change 3 which was an unexpected positive surprise. After much fussing with various 12ax7's and replacing the bare wire board jumpers I was still no farther ahead with eliminating the phono section rushing noise that occured at about an 11 oclock position (my normal playing level). I decided to swap in 12AU7 instead. Big smile on my face as I turn the volume knob all the way up and not a rushing sound to be heard. Granted, my normal playing position has now changed to 1 oclock but sound is gloriously quiet, musical and all 12AU7's tried are quiet.

So more to post later once the new diodes arrive.
sorry, busy with other things. So since last time
1) in the phono bypass caps the 0.15uf obbligatos were nice, open sounding... however the cap casing is a hum magnet and microphonic. So yanked them out and threw in some Mundorf Supremes temporarily
2) the Vishay sinter glass diodes are great, fast. Believe I'm there for power supply clean up
3) seems the rushing noise finally cleared up completely in the phono section after I rechecked lead proximity and cleaned up solder joints.

I plan 1 last step, to add VCap teflons as the phono bypass caps at end of month. These do take about 60-90 to break in which would be about May to report back.
You might wish to try a JJ E83CC or better yet an E803s I think it is. Very low noise tube. Did you not change the gain by changing to a 12AU7? You may just need some good low noise resistors around that set of tubes rather than change to a 12AU7. Just a thought.
I actually talked to a very helpful gentlemen at a shop in Springfield that does repairs on audiophile gear. He advised strongly against replacing any resistors in the phono section as they were all there for precisely calibrated RIAA equalization. And since the noise went away after I did some circuit cleanup, all is well
Hi Davide,
I noticed this part of your journey: "also replaced the stock electrolytics on power supply section with Nichicon fine gold caps but that didn't seem to cause a noticeable change"

Since the PV10A uses polypropylene, not electrolytics, for the power supply, I am wondering what is going on? The only 'lytic in the power supply is a single cap for the filament circuit, or the "heater" as they say.

there's a few small value electrolytics in the power supply part of the circuit board. Entirely possible that they have no role in signal path
I've accidently stumbled onto a need to update this thread. Bought some Clarity CAP MR's 0.22 630V with the intent of upgrading the Rel Thetas on the Prima Luna amp board... that didn't work out well when you had 1/2" to play with for cap width and the new caps are 1" in width. So I decided to use the 4 caps as bypass cap's for the 2uf Theta's in the CJ PV10A and so far its a resounding success. One of the reasons I kept flip-flopping between the PL pre section and the CJ was because while the CJ sounded "just right" in the mid range it was too polite in the treble, even had some signs of distortion. Whereas the PL sounds airy, clean in the highs but in the mid range details just don't pop out the way they do with the CJ. After add of the Clarity CAP MR's, that experience of details popping has extended into the treble, and top hat cymbal resolves sharply, no splat or polite clap. I'm really enjoying listening to small group jazz now, amazing the amount of subtle percussion details.
I've grown suspicious that the Rel Thetas are behind why female vocalists in the same octave range sound sibilant, a kind of "glare" that was there before but muted... now with the MR bypass caps that glare can't hide. One of the pains of doing CAP upgrades is that you are limited by space for what you can substitute and at 1.8/2uf there aren't a lot of good options at 1" diameter or less. I have some Auricap XO's on order as a first stab, workable alternate suggestions welcome(staying away from Obliggato as they mechanically ring). Will update in about 3 weeks after the XO's are in and have had some playing time.
The Auricap XO's didn't last 2 weeks , bland and uninteresting. I've also tried using Rel Teflon 0.22uf bypass caps for the Rel 2uf thetas but they sound less dynamic, less fluid on vocals compared to when the Clarity MR caps are in as bypass caps. And the glare I was complaining about in February seems to be resolving as I make source improvements.