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
davide256's avatar
davide256 OP
399 posts
 
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.
hifigeek1
770 posts
 
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.
davide256's avatar
davide256 OP
399 posts
 
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
hukkfinn
28 posts
 
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.

Cheers,
Hukk
davide256's avatar
davide256 OP
399 posts
 
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
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