tube upgrades for CJ PV 10?

[bilgewater]

Hi Y'all,

Well I recently acquired a cj pv10 preamp, w/ phono preamp.

It is my first CJ product or tube amp. I bought the pv 10 hoping it would offer an improvement in sound quality from the Rega Fono MM preamp I'd been using previously. It wasn't a giveaway price. Everything is working just fine, but...

In my initial a/b comparisons of the two phono preamps (using Joni Mitchell's HEJIRA as my test lp), I am having a hard time telling much of a difference between the preamps. I have the pv10 volume at about 9 o'clock (much louder means distortion, which the Rega would never do).

I haven't yet checked the tubes (which I'm told were replaced at CJ factory by prior owner). After more a/b work, I'm wondering (already) about possible mods or upgrades. Any ideas about tube replacements that might take this stock pv10 to a higher level?

The tube complement is 2x 12ax7; 2x 12at7; 1x 5751.

My goal is warmth, richness, and sonorousness for acoustic jazz (mostly) and also seventies soul and hiphop vinyl.

The system is what I hope qualifies as intelligent and gently used mid-fi:
Rega p3-24 table
Linn Classik SS amp (replacement Rega fono MM preamp)
Vienna Acoustics Mozart Grand speakers
REL t3 sub
assorted ICs and cables: Van den Hul, Linn, Audioquest...

Any thoughts? Pointers?

[admin]

bilgewater,
First, welcome to the site! It's nice to have you.

As for tube replacements you may want to talk with Ed at CJ and ask him what he thinks would be good alternatives. I'm sure other members may have better advice than myself as I have actually never owned a CJ with phono section. I had the PF2 and PV12 but they were both Linestage versions. If you think you have a tube issue, one thing you can try is swapping the tubes and see if that changes the acoustic characteristics. I used this to trouble shoot a bad tube in my PV12 (I talked about this in the "troubleshooting" section of the site.) Obviously you can only swap the 12ax7 and 12at7 positions.

One thing I would like to ask however is: What kind of cartridge are you using? This is really important in helping you with the issue. You may have a mismatch between the cartridge and the gain setting on the PV10. The 9 o'clock position is pretty low and if your getting distortion at higher levels it makes me wonder whether the gain is too high on the PV10. I know that many phono sections have a gain selector inside the unit, but I'm not sure about the PV10. It should say in the manual. Is the volume knob at roughly the same place for both turntable listening vs linestage inputs (ie CD player) or are you cranking the volume knob higher for other sources. If there is a big mismatch, your issue may be poor cartridge gain setting on the PV10. If the gain is appropriate, you will find the music sounds much more detailed with a fuller soundstage and much less distortion at higher volumes.

[bilgewater]

Hi,
Thanks for your thoughtful response. As it would happen, I am only using the phono stage of the PV 10. At the urging of folks on another forum, I have the line going from TAPE OUT to AUX IN on the Linn integrated amp so the volume position/distortion/gain on the CJ is now moot.

At this point, I'm embarrassed to say that I don't have a proper power amp per se and only need the phono stage aspect of the CJ. The Linn Classik amp has an excellent cd player integrated into it.... I know, mid-fi stuff.... For now.

My Rega TT has an elys2 cartridge, which is MM.

I am looking into improving the tubes on the phono stage, though. Probably something in the vicinity of Tungsram or NOS mullard 12ax7.

[admin]

First, that's a fine setup! I wouldn't consider it mid-fi, sounds like a very nice setup. I am still not convinced that the phono preamp gain is not your problem. If you able to quickly rewire, I would try using the CJ as a standard preamp and see if line level inputs have you turning the volume knob to approximately the same place as with the phono input. Remember, gain varies greatly between phono preamps. For example, my Jolida JD9 phono preamp can be set to have a gain anywhere between 35 db to 95db! With the improper setup to my cartridge it sounds absolutely horrendous and distorted, with the correct setting it's a beautiful sound! I tried looking up your cartridge on needledoctor.com but it didn't list the recommended gain setting. I'm sure it's listed somewhere. The PV10 phono gain is rated at 48.5 db so your cartridge has to match this, or at least be pretty close. If you getting a lot of distortion (and your tubes are not inherently bad) then replacing tubes may not improve the situation (and that's a lot of money due to all those tubes!).

Once again, I would do a quick test of line stage input volumes compared to the phono and see what you get. Keep us informed, would love to know what's going on!

[JimMasterson]

Hi there,
I was excited to read your question because one of the most spectacular moments in my audiophile life was hooking up a CJ PV10-B as a phono preamp only, the way you have done. I loved, loved, loved that phono pre.
Your first job is to determine which tubes are for the phono stage. Ed at c-j says that the phono stage tubes in a PV10 are the two 12ax7s and *one* of the 12at7's.

The phono stage tubes are the 3 tubes on the left, inside the amp. The two tubes that are together over to the right are for the line stage.

To get "the good stuff" for these tubes, I recommend old Amperex. Like, from the late 50s or early 60s. This includes the Amperex Bugle Boys, but others are wonderful too. They just have to test strong. If you need help finding these, let me know. Also *excellent* but a little less romantic and very neutral are Telefunken (considered the best by many, and therefore, expensive). On the other extreme, good but very glow-y and warm: old Mullard. A safe "second place" is old Brimar and third place is old RCA. Anything modern will disappoint (Svetlana, Tungsol, Sovtek, new "Mullard", etc) but if you must go "new", JJ are maybe the best. All this in my experience, of course, just my opinion.
Good luck!

[Joe Appierto]

Hi,

I'm using my PV10A for the same purpose as you, just as a phonostage, and I'm running it with the volume control set around 12:00 with no distortion at all. However, I'm using the Main Out on the 10A rather than the tape loop. So, assuming the correct type tubes are in their proper places, I'm wondering if there might be a problem with the Tape Out on your PV10? Just as an experiment, you might want to try switching the output connectors from Tape to Main and see what happens.

As to tube choices, I'd have to agree with the poster who recommended Amperex. I think they'd be what you're looking for. I'm using Telefunken smooth plate 12AT7 and 12AX7s and they might be more neutral sounding than your stated preference.

Good luck in resolving this issue. Once it's working properly, I think you're going to be quite pleased.

[Headrush]

Hi,

I have a PV11 that had terrible distortion on the phono stage and tried all manner of tube rolling to try and sort it but nothing worked. I did eventually notice 2 tiny square shaped components soldered to the wires on the inside of the phono inputs that just didn't look right, like some kind of afterthought in the design. A guy on another forum suggested they were resistor shunts that should not be there and were probably installed by a previous owner to match his cartridge. I took a small pair of snips and a giant leap of faith and cut them out. Turns out the guy was right, it now works perfect and is so loud I seldom raise the volume past 11 o'clock where it also starts to hiss, not that you would notice at that volume. It's just an idea and I thought it was worth mentioning.

It might also be worth mentioning that your PV10 may be phase inverting as is mine, making it hard to do A/B phono stage comparisons without constantly swapping the speaker wires over.

As for valves, I have 2 Mullard 12ax7 CV4004, an RCA 5751 and another Mullard 12au7, as there are 4 valves on my phono stage. I have no idea if this is a good combination as my ears are shot to bits but it sounds fine to me

[billyz]

I can highly recommend the Amperex Bugle Boy late 50's in the phono section. They are 3D sounding and very full as well, nothing lacking. Others I have tried and liked are Mullard ecc83 and Telefunkens. I have not tried but think would be very good are the venerable RCA 7025. If I had a pair of NOS Tungsol 12ax7's I would try them as well. RCA Blackplate 5751 are great . For 12at7's , Telefunken, Amperex even JAN RCA's 6201.

[Corben Dallas]

Hi,
maybe you should have a look there :
http://www.thresholdlovers.com/articles ... en&pg=1200
For the tubes 12ax7 I should say also Electro Harmonix and Telefunken smooth plates too...
Cheers

[mike300zx]

Hi there,

This is a very interesting and informative post - thanks to all who have contributed.

I also have a PV10A, and have not replaced the tubes for over 10 years. I have not noticed a deterioration in the sound quality, but I guess if it was gradual over that time I may be pleasantly surprised if I replace the tubes. I'm not looking for an upgrade, I want to keep to the original sound I have had for years and love - at least for now anyway.

Where is the best place to source replacement tubes - I have just moved to Honolulu and will also be looking for someone to convert my PV10A to 110v as well.

I had been running them through a pair of bridged Plinius SA100B's driving my Polk SRS 3.1TL's. I had been using a Sony XA777ES as the front end, however, recently I have found using a laptop through an Apogee mini-dac is comparable, and produces an overall lovely sound.

I have had to part with the Pliniuses as it was going to be a major job to convert them to 110v (they didn't have dual voltage transformers), so I have sold them and I'm looking for a replacement - currently looking at a pair of benchmark AHB2's.

Any thoughts, or help regarding tube replacements for my PV10A and also on the conversion to 110v, would be greatly appreciated.

Thanks, Mike.

[tubegroover]

I purchase all my tubes from Andy Bowman of Vintage Tube Services. He's very knowledgeable and you will get quality tubes at a fair price. He'll also go through the different manufacturers' to help you find exactly the sonic signature you're looking for. Good luck!

vintagetubeservices.com/

(616) 454-3467