Question for tube aficionados

I have a vintage Conrad-Johnson PV 11 preamp.
 I’ve always re-tubed it  with the cheapest tubes from Tube Depot (e.g. Electro-Harmonix 12AU7 and 12AX7, Sovtek 5751 and the like.). I’ve been very happy with the sound.
 My question is:
 Would it be worthwhile to spend more money on more exotic tubes?
  Would there be any appreciable difference in the sound?
 I’m powering the system with NuForce Reference 9 V3 monoblocks.
I think lowrider57 may be incorrect. The Mullards could be new production or old. The Yugoslavia 12AU 7's are definitely old stock. They haven't been inproduction for 20+ years. When this unit was first produced I don't think  new production Mullards were available - my guess is that they are more probably old stock and I think that the NOS and new production do not have the same tonal qualities. 

I'm not familar with your pre-amp but I suspect that the V1 and V2 positions are likely the positions most affected by tube changes. If that is so, and if I wanted to play with tubes changes, I would start there keeping in mind that different brands have different tonal qualities and it helps a lot in selecting tubes you want to try to have some 'tonal' goal and try tubes that have a similar tonal signature.
@newbee , you may be right. I traced the PV11 preamp back to at least 1992, so the Ei and Mullard could have been NOS. But CJ is now re-tubing the unit, and $310 is a very low price to include 2 NOS Mullards.
+1 lowrider57. I’m not suggesting that the CJ recommended tube option is a bad one. For that cost I’d would pursue the NOS tube pathway. I like the idea of trying the RCA tubes as earlier considered above. I’d have CJ clarify if their tubes are NOS or current production. Again their choices may be very good sounding. Truth is there are many good tube rolling options for the 12AX7 and 12AU7 family.

I have a VTL 2.5 preamp
I ran OEM 12AU7 JJ’s up until about 4 years ago.
I went to NOS 12AU7 Amperex Bugle boys - a significant improvement over the JJ’s
I just got NOS Telefunken 12AU7’s - another significant improvement over the Bugle Boys. There’s a new level of openness

I asked CJ what the tubes were, and surprisingly the reply was  the 12AX7 Mullards are NOS, the others are new production.
The question then becomes, which Mullards are included?
One word “ TELEFUNKEN “! I have NOS 12AU7’s ( E82CC, ECC82) in Telefunken , Tesla, Seimens , Mullard , RCA, Tungsram . They all are better than new stuff . They have distinct tonal differences . I use 5 different NOS rectifier tubes which raise or lower the voltage and effect my power tubes . So driver and rectifier tubes are all NOS. They last a long time . Power tubes - I have NOS GEC KT88 and KT66 , NOS Tungsol 6550 ( 3 hole ) , and SED Winged C 6550 and 6L6GC. They are better than current production tubes and more expensive. New production, I have Gold Lion KT88 and KT77 ( very nice sound ), Psvane TI KT88, Tungsol KT120, JJ KT77. Of the new stuff I am fond of the GL tubes . But for your application Telefunken NOS. FYI Brent Jesse’s site gives a very accurate description of SOUND from various tubes . FWIW, I have $3k in tubes for a $1500. Amp , so you see where this can take you 😝. Shoot me a message if you have specific questions . Happy Listening , Mike B. 
I recently upgrade my Cary 120 with new Gold Lion KT-88's and Psvane 6sn7.
Previously I had Gold Lions, but they had quite a few hours on them. I also had Tunsol 6sn7's
The Psvane Grey bottle are a matched Quad and the Gold Lions are a matched octet.
I'm constantly blown away by the increase in soundstage and detail, both high and low.
Psvane makes both a 12au7 and 12ax7.

I will be upgrading my Cary SL98P F1 from the Tunsol 6sn7 to a Psvane grey bottle matched quad.
I like the Psvance, that much.
The difference in sound between NOS and new production tubes is slight and you will spend a lot of money finding NOS tubes that are (1) not fake, (2) not microphonic (3) not noisy. My 2c worth. I gave up the chase years ago and now use matched and tested JJ or Sovtek tubes.

Also, CJ amps of this vintage typically use circuit designs that are not optimal to produce a "tubey" sound. They are also prone to oscillation with the wrong tube choices because of CJ's refusal to follow good design practice and use grid stopper resistors. The difference NOS tubes will make is like cables - not much. I'd stick with what works.
"The difference NOS tubes will make is like cables - not much."

Interesting analogy except with cables you can show them off, not so much with many tube designs, particularly preamps. Just like anything else in audio, the depth of one's pocket is the only limiting factor.
Hello, I’ve owned the PV-11 for over 20yrs now. It was my main preamp for 10yrs but I have moved onto a AR SP-11 Mk 2. I still have the PV-11 in my collection of preamps. The tubes that sounded the best to me in the PV-11’s linestage is the Amperex 7316. I think other Bugle Boy 12AU7’s may sound good also but the 7316’s were the most musical and revealing tube for me. Keep in mine that the linestage of the PV-11 is fine but it’s phonostage is totally awesome. 
I'd agree that not all NOS tubes are genuinely "new" old stock and a reputable dealer is worth seeking out.  
Not every NOS tube is by default always better than current production,  it depends on numerous variables.  I can vouch for the upper level of the Psvane tubes for example. 

Based on my experience I believe that you can find high quality NOS tubes if using a honest dealer/vender.
Raindance 3-16-2018
They are also prone to oscillation with the wrong tube choices because of CJ's refusal to follow good design practice and use grid stopper resistors.
Interesting point, which I hadn't been aware of.  I couldn't find a schematic for the PV11, but I took a look at schematics for the PV10 and PV12 which are available at  And I can confirm Raindance's assertion for at least most of the tube stages in these designs.  I have no idea why CJ wouldn't have put grid stopper resistors having at least relatively low resistances into these designs, but as Raindance indicated not including them is definitely not good design practice.

The following article provides good background on this subject, even though it is oriented toward guitar amp applications:

-- Al
Just another note, if anyone knows more about 12au7, 12ax7,5751 tubes, it’s me. I’ve been rolling tubes for years and I have a huge stock of all the top vintage brands. I can’t believe how people comment on subjects they know nothing about. No wonder people get so confused when they need direction. I tried a lot of tubes in the PV-11 line stage and the 7316 will be the tube that will give you most satisfaction. It’s because it is very revealing but smooth and musical too. If you desire a more analytical sound, RCA clear top.   Mullard Old Logo 1960’s 12au7’s are my 2nd favorite along with the French made Cifte 12au7’s.  I personally felt the phonostage of the PV-11 was way superior to its linestage and I actually found putting in all quality tubes in the phonostage didn’t improve its sound. So for the  phonostage, I used a vintage 5751 black plate triple mica (doesn’t matter their all great), basic current production Russian 12AX7’s and a Mullard 12AU7 or 7316 Amperex for the 12AU7. Good luck.  
Very interesting posts!
Also a myriad of suggestions.

I agree the phono stage of the PV11 is awesome.  Records sound way better than CDs.
Thank you lowtubes for your expertise.
 I will look for the Amperex 7316.

I owned a PV11 for many years... a truely wonderful preamp.  I loved it.

What is wrong with calling CJ directly and talking to them? 

CJ knows the tube market really well and can help you make a decision.. they have seen it all.  Getting other opinions is great, but why this apparent aversion to calling the manufacturer?   CJ is a good company with good folks who know what their stuff.

I would start with CJ first, then branch out.

Bruce in Philly
I have a near 25 year old Audio Research pre-amp that came new tubed with Chinese 6DJ8.  I liked the sound quite a bit and decided after a few years to experiment with tubes. Holland, Bugle Boys, Amperex and so on came and went.  ..many different manufacture countries and brands  rolled in and rolled out, until I encountered a Siemens & Halske 6922 grey plate from the late 50's - early 60's.  That was the tube of choice for more than decade until I tried a 1959 Valvo Pinched Waist 6922 Cca, which was great for about 2 years of light use when it began to fade musically. Now it's a 1975 silver single wire Reflector 6N23 which is king of the hill.

The point being the right tube(s) can make or break your sound.  Do some tube rolling. What doesn't work for you can probably sell easily on eBay.
I used to have both the PV11 and PV12. NOS tubes did sound better, but if memory serves, seem to recall in both preamps the tubes were run in a current starved condition. You may want to measure the current/voltage flow through the tube. I dropped the plate load resistors and got much more open sound, but do not remember the values.

Still wish I had my PV5...that preamp made real music.

doing the CJ tube replacement for $310 would be a quick and easy way to get things squared away. Then, down the road, you could roll some tubes. But I'm sure part of that $310 is a fee for their special knowledge of the right tube combination. Maybe not the best value per se, but definitely a quick and easy way to clean the slate and start from a proper baseline. 

But i would have to agree that the Gold Lyons would be more of a lateral move. Absolutely nothing wrong with that, but i just try to make a little bigger move when I do an upgrade.

I'm not talking about exceeding the $130 budget either. But the sound quality gains will be significant, especially since preamps tend to have more influence on the final sound characteristics than amps (and yes, I know, I know, some of you will argue with that ... yeesh).

In fact, you may just ask yourself, "why did it take me so long to figure this out ... :)" 
As a general note, please remember also that replacing a tube alone is not good enough. Compensating tube production variations, tube aging (and, especially, when using equivalent models) always demands a check and adjustment of bias voltage. I experienced surprisingly significant sound differences from the bias voltage differences of 5%. To make it more challenging, certain systems will benefit from setting a bias voltage that is different than the one recommended by the amp manufacturer. Additionally, my recent observation indicates that the replacing tubes and adjusting bias can also introduce embellishment and extension of trebles that can be easily taken for increased resolution while it only adds graininess.
Hi Folks...

Need to correct almarg and raindance about those grid resistors.  I was in touch with Jeff Fischel, now heading up c-j, about those PV-11 grid resistors.  Apparently the sources the previous posters used were wrong. Here is his reply to me:


 Actually on all 3 of these models we do employ grid resistors on all gain stages , typically a 47R5 resistor. All CJ preamps use grid resistors either 47R5 , 100R or 332R.


 Jeff Fischel

conrad-johnson design inc.


Guess doing it correctly is one reason their equipment consistently sounds so good.

Actually on all 3 of these models we do employ grid resistors on all gain stages , typically a 47R5 resistor. All CJ preamps use grid resistors either 47R5 , 100R or 332R.
Thanks, Coppy. Good to know.

That information doesn’t appear to be consistent with the schematics I looked at for the PV-10 and PV-12 at, and 47R5 (i.e. 47.5 ohms) seems much lower than usual for the value of a grid stopper resistor that would be effective in these kinds of designs. But in addition to the high confidence I would have in an answer provided by Mr. Fischel the bottom line would seem to be, as you said, that "their equipment consistently sounds so good."

Thanks again. Regards,
-- Al

I have no idea what you’re talking about, but I can tell you the preamp is terrific,
even after all these years!
Concerning the CJ PV11 amplifier, does anyone know if the two 12 AU7 tubes that drive the line stage have any effect on the phono stage at all, or do they just affect the line stage alone?
I have a Unison hybrid integrated which uses 2 12au7s in preamp end.  I have used two different Mullard 12au7s, RCA Cleartops, and Radiotechnique, but the Siemens 12au7 NOS (got mine from Upscale) beat them all.  Beautiful full bottom end, great midrange, and an open and fantastic top end, no brightness but crystal clear.  Wonderfully dynamic.
rvpiano, Check with CJ, but FWIW I can't think of a single reason why tube selection in the line stage would affect the performance of the tubes in the phono stage, except for the obvious one is that the phono stage signal passes thru the line stage therefor any tonal changes brought about by the line stage tubes will be reflected in the sound from the phono (or any other) source.
Hello Rvpiano, I had no intention on visiting this forum again but I’m on a email list that generates recent and past discussions and I browse the list for interesting topics. 
So to answer your latest question, I believe that the unit can play it’s phono section without tubes in the line stage- but I also believe that when tubes are in the line stage, it may affect the sound of the phonostage slightly. 
When I used my PV-11 as my main preamp, I chose to use the purest and most revealing digital / cable front-end but for for my phonostage, it was very different, I chose a very musical cartridge. This was how I balanced both sections of the PV-11 to sound close and very good.  I still do not understand why CJ would make preamps where one stage would sound so superior to the other.  This is not the only preamp they have done like this.  I believe CJ really believed at the time that digital sources were all analytical and hard sounding. As I mentioned before, my main preamp now is the Audio Research SP-11 Mk2 and it has a wonderful phonostage that is definitely on par with its line stage but I actually prefer the sound of the phonostages from CJ tube preamps.  I have my system setup to use the line stage of the AR but my vinyl is played via the phono section of my CJ PV9a.  Rvpiano, if you check eBay, you’ll see 7316 tubes labeled all different names, but you want the ones made by Amperex and it does not matter if the getter is round or D shaped, they sound identical. Good luck enjoying your PV-11 and try balancing your system as I did when I had my PV-11 as the main pre. If you ever think about upgrading, don’t do what I did and sell the PV-11. It took me years before I got mine back.  Keep it because many of Conrad Johnson preamps made in the 1980’s have killer phonostages. My favorites CJ phono sections are the, CJ Premier Three, PV-5, PV-8, PV9a, PV-10a and PV-11.  All of these have their own special tube magic.  

It certainly is true that the phono stage of the PV11 is wonderful.
 I’ve placed a bid for a pair of Amperex 7316 tubes on eBay.
Meanwhile, I’m sampling NOS Telefunken AU7 tubes.
Amazingly, these tubes have brought the sound of the line stage very close to the phono stage. If I win the bid for the Amperex, I’ll compare them to the Telefunken.

I’m not surprised that you notice such a significant improvement in the sound quality. The point numerous posters have made on this thread is true, better quality tubes are unquestionably impactful. Congratulations. I didn’t understand the comments of some who suggest that there wouldn’t be much of a difference. Average quality tubes will only restrict/limit the true potential of your preamplifier. The basic design and circuit of the PV 11 is good, but held back by mediocre tubes in the line section. 
CJ’s answer to the question of the effect of the line stage tubes on the phono section of the PV11:

“If you are connecting the PV-11 MAIN OUTPUT to your power amp, then the
12AU7 in the line stage would affect the sound quality. If you are only
using the record output then the 12AU7 are not in the audio circuit.”

Well, I got the Amperex 7316 tubes today.  Excellent tubes.
In preliminary testing, comparing them to the Telefunken 12AU7’s, I found the Amperex to have stronger bass and a bigger and more forward presentation than the Telefunken, but the Telefunken has a more refined and perhaps, clearer sonic picture.
Both are excellent tubes at almost the same exact price. My dilemma is, I can return the Telefunken, the Amperex, I cannot.
I don’t know if it’s practical to keep both.
If you plan to live over a year or two, wise to keep both .
Their value will not decrease .
I’ve owned the PV-11 for over 20yrs now. It was my main preamp for 10yrs but I have moved onto a AR SP-11 Mk 2. I still have the PV-11 in my collection of preamps. The tubes that sounded the best to me in the PV-11’s linestage is the Amperex 7316. I think other Bugle Boy 12AU7’s may sound good also but the 7316’s were the most musical and revealing tube for me.
I tried a lot of tubes in the PV-11 line stage and the 7316 will be the tube that will give you most satisfaction. It’s because it is very revealing but smooth and musical too. If you desire a more analytical sound, RCA clear top.   Mullard Old Logo 1960’s 12au7’s are my 2nd favorite along with the French made Cifte 12au7’s.

@rvpiano, a couple of questions;
Have you given the Amperex enough time to burn-in? Run them for 40 or 50 hours and then evaluate them.
Do you know if these are 1950s issue and what is branded on the label?
   The 7316's should present a 3D image with a sweet midrange. I agree with you that "Telefunken has a more refined and perhaps, clearer sonic picture."
But, as others have stated above, I find the premium, low-noise Amperex more musical. I'm not discounting your findings in any way, but I wonder if they need more run-in time.


You’re absolutely right,  As I mentioned, the tests were only preliminary.
I haven’t given the Amperex enough time yet to burn in yet.
Im going to leave them in for a while to give a more thorough evaluation.
Thanks to all of you that gave advice about NOS tubes.
They make a HUGE  difference in the sound of my set.
I sold the Belles. They were definitely not compatible and were not powerful enough to drive my system.
The NuForce are much stronger, and they sound fabulous.
Modified Dalquist DQ 20’s.
The Belles just didn’t push them hard enough for impact.

Interesting.  The figures in this review suggest an average-ish impedance curve.

Did the modifications make them harder to drive?

Could be.
 The bass response is far better than the original was.
Really quite impressive!

The main thing, though, is that it just sounds better with the NuForce.
Objective evaluation of improvements in a stereo system is hard to arrive at.  There are so many subjective factors involved.  So I pulled out the Chesky “Ultimate Demonstration” disc that I had listened to prior to tube and amplifier changes. This is a very demanding disc which revealed severe limitations in my old system in just about every area.
Listening to it again now, I found the system to pass most of the tests very well. Of course, you could say there’s at least some degree of subjectivity involved here, too.  But, at least it’s somewhat objective.
RV, I was really lost about the Belles ,my 150a Reference VII has no problem driving my 4ohm , 87db Totem Sig Ones which are hard  to drive .
Knew nothing about the DQ 20's . Worked internet , 4-5 reviews all noted how hard it is to drive, several said hardest speaker to drive they had ever encountered .
One said 250 watts a side was bare minimum , 400 would be better, guessed its to be a 82db load .

@schubert Very interesting, makes a lot of sense, and explains the situation.

@rvpiano Have you ever thought about stepping up to the Bel Canto Ref600M's?  From everything I've read, they could be your dream amps.

At the risk of being a homey .The BelCanto 600M's are only class D I would consider .
durk. Most Bugle Boys sold are fake .
It seems that the Telefunkens and Amperex are different enough so as to require an either/or choice. Some have said that the Telefunkens and Amperex are no better than new tubes like the psvanes... has anyone compared all three side by side?