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.
7c67ab18 c2ce 4b45 9523 fc4a71684ce0rvpiano
EH and Sovteks can be amazing sounding tubes so those are well chosen...Gold Lion 12AX7s (new ones) are great and not too pricey…NOS Mullard 6201s are also very nice, and yeah…you can tell the difference. I now use 6SN7GTBs in both my SE power amp and preamp (that has 4 of them) and have been having fun rolling around that tube…NOS USA Amperex, Sylvanias, blah blah…and they all make different tonal flavors.

Can 6SN7GTB‘s be used in place of 12AX7 and 12AU7?
rvpiano, I want to congratulate you on taking the next step to audionirvana. You are in for some silly happy surprises, big grins, and perhaps even some giggling like a little girl-- like the rest of us -- when we find the right tube for the job!

I’ve used tubes for 10 years or so now in various uses in my audio chain. and like you, questioned the tubes abilities, and the higher costs of "better" tubes.

If you just wanted to jump into tubes and get something going soon, I would suggest just calling perhaps 3-4 tube sellers to ask them what they would suggest based on your particular unit (but make sure to call Upscale Audio- they are knowledgable, will help guide you, will ask you what you are powering, etc. In fact, when you buy tubes from Upscale on their website, you are required to type in the type of tube unit that you would be using the tubes for-- in order to make sure they match electronically.

Sovteks and EH are .... okay. But the next level up you will hear differences in sound... say to the Gold Lions, as they said above. But the next level would be like modern made tubes that are well-designed and manufactured with good Quality Control (like PSVane, modern Mullards, etc), then like the NOS tubes that dont cost an arm and a leg, at the entry level rung, and on upward. I always try to buy the entry-mid level NOS that have really "low microphonics" means that the tube should have been tested on a tube-testing machine to check its current condition. eg, Upscale does this, like tube depot, etc will write down the "matched" electrical voltages/etc of each tube. so you know you got a "matched pair", eg, when I bought 2 tubes for a preAmp, and when I bought 8 KT88s.
But what type of tubes are you looking to upgrade right now?

Thank you for your input (also wolf_garcia.)
what do do you suggest, knowing what I have now?
Gold Lions?

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To your question to Wolf, no you can sub in 6sn7s for 12au7s or 12ax7s

Here's the link to Brent Jessee' website (sells mostly NOS tubes) if you scroll down a bit to the yellow section where you see different tube types listed click on 12ax7 and it will bring up not only his list of available tubes but impressions on various respective brands; you can do likewise for 12au7, etc.  (Note: I am not Brent nor affiliated with his company other than as a customer) - Might be helpful. Also , if you call him , say Andy at Vintage Tube Services and tell them what type sound you are looking for they can steer you accordingly. 
Opps meant no you can not  sub in 6sn7s for 12au7s or 12ax7s
Oh, do try some other tubes than the EH and Sovteks!  They are "adequate", IME, but certainly nothing special.  I have had great success trying 5751's in place of 12AX7's at the driver station for an EAR 890, and there are great options for voicing the amp in a direction you desire, all of which are definitely superior to your current tubes for musical finesse.  I like RCA 5751 Triple Mica Black Plates when I want a richer presentation, a "warmer" influence, as it were.  If you want a more articulate (but potentially leaner) presentation, try a GE 5751 Triple Mica Black Plate.  Now, when you want the best all around performer, IME, try a Sylvania 5751 Triple Mica Black Plate.  That is where I settled, but each amp, system, person is different....

Also, Joe's Tube Lore is definitely worth a read through over at AudioAsylum (in their FAQ's section for tubes).
You’re using pretty decent tubes but as others have pointed out you can definitely move to a higher level for improved sound quality. You’ve been given some reputable tube vendor commendations. I can vouch for Vintage tube services. Much knowledge and very good selections from Andy. You can certainly exploit the CJ PV 11 true potential with better quality tubes. 
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@elizabeth I hear what you are saying, and for some manufacturers this is fine, from Schiit (or is it iFi?) that have the sockets. But i think they might limit the quality the OP is after.

I’m not a purist, but I dont use the sockets that allow other tube types, b/c it is just another thing in the way of the audio chain. And the OP is looking for good tubes with good bang for buck. IOWs, I personally would not put a socket on a $75 NOS tube.

TBH, im not familiar with your CJ PV11, so i did a quick look up- this is from the 90s? and uses 3 different tube types? of course it is fine to have an older model, but that will tell us more about its general circuitry under the hood. Some amps can handle substitutions, some cant. Some pre amps now (LTA MicroZotl) have a choice of 6SN7 or 12AuX, b/c the circuit board and electronics inside support these different electrical platforms.

@rvpiano: i would like to make some recs on tubes, but it would help me/us to know:
1. Do you have a budget per tube or to replace all 6 right now? or replace just some? Whatever you do, swap out all the tubes of the SAME type. eg, dont replace one 12AU7, replace all of them at the same time. you probably guessed this, but some people dont.
2. I know the Nuforce class D amps you have, but what speakers do you have?
3. What particular aspects of sound quality do you want to change? more or less hi frequency? more or less mids? more ore less bass? more balance overall? a "sweeter" sound? a dryer sound? a colder sound? a bigger soundstage? a smaller stage? a more aggressive or laid back sound?  you get the picture....
Hi RV,

First, I note the following statement in the manual for the PV11:

It is well known that tubes of a given type vary sonically depending on the manufacturer. We have chosen the brands of tubes we supply based on extensive auditioning of available brands. The choice of brands has been made solely on the basis of sonic performance without regard for either cost or prestige. We know of no vacuum tubes available which will improve the sonic performance of your PV11....

... Please note: The indiscriminate substitution of type 12AX7 tubes for the 5751 will seriously degrade the sonic performance of the unit.

Also, apparently four of the six tubes in the PV11 are used in its phono stage, and only two in its line stage. And I would not necessarily assume that a given tube is likely to exhibit similar behavior in the two kinds of applications.

Given all of that, it may be worthwhile contacting CJ and asking if they can tell you what tubes were originally used in the PV11.

Beyond that, FWIW like some of the others I have had fine results with Gold Lion reissue 12AX7 and 12AU7 tubes, in my case in line-level and driver stage applications in a Chinese-made Paxthon integrated amplifier I used for a while some years ago. They handily outperformed a number of vintage tubes I also tried in that amp, including some vintage Telefunkens which go for considerably higher prices.

Good luck. Best regards,
-- Al

Never sub a 12 type tube for a 6 type tube. The number is the voltage. Hence 12ax7 is 12 volts! BTW, a 5751 has 30% less gain than a 12AX7!
The new mullard 12ax7 are very good....
Amperex Nos or decent testing units 12AX7 
orange globe 
Thanks to everyone for their suggestions.

My speakers are modified Dalquist DQ 20’s.

Overall, the system is fairly well balanced.  What could be improved is occasional brightness in the treble, especially in the line stage.

 Ideally, I’d like to replace all six tubes, depending on the cost.
Vintage pre-1970 GE, RCA, Sylvania, Mullard and Telefunken are still the best made and sounding of the 12a*7 types! Far better (and longer lasting) than present day production! That is why they command high prices!
Cheap present day 12a*7 types will never equal the sound quality and lifespan of vintage types!
I have always gotten solid advice and feedback from Brent Jesse, Andy at Vintage Tube Services, and Upscale Audio. I’ve purchased from all three over the past 20 years, and have not gotten a bad tube from any of the three. 

I would start by replacing the two 12AU7s in the line stage with a very high quality matched pair, as all sources will run through that preamp stage. Replace each additional tube type in phono section in stages to evaluate what each is doing to your sound for your future reference. You may notice some tube positions make larger differences than others.  Have fun!
I've had three different CJ tube preamps over the years.  I found that European as well as some Japanese NOS tubes made a significant difference/improvement.  Be careful to get low noise tubes, particularly in the phono section.
Having tube rolled integrated amps, phono stages, and amplifiers, I can say that tubes can make all the difference in terms of gain, clarity and other aspects. The tubes in your CJ pre will make the most difference. I replaced the stock 12ax7 tubes in my pre with GE 5751 tubes and it made an incredible difference in terms of clarity, gain, presence, and soundstage. Those tubes were $60 each, but it was an immeasurable investment.

But I also did my research in terms of what tubes were the most complementary to my unit beforehand.

@hedgehog gives good advice above about how and when to replace tubes: line stage first, then phono section, and make mental notes of the sound changes as you progress.

1. Line stage: 2 x 12AU7: I’m assuming
2. Phono: 1 x 5751 and 3 x 12AX7

12AU7s: Lots of good opportunities here.
The NOS Mullards are end stage tubes for many, meaning once you hear it, you never let go of the tubes. I bought 4 matched of these tubes for about $125 each after shipping, taxes, matching, etc. from Upscale last year to try in my PrimaLuna tube integrated. I also needed a softer top end b/c I have ribbon tweeters in my speakers, which can burn your ears with more aggressive tube profiles.

The Mullards (specifically the M8136 model from Upscale) are expensive, yes, but everything they said was true: softened but very beautiful top end slightly rolled off. The soundstage is to do for, it puts the band in the room with you. Not many cons to this tube other than a slightly rolled off bottom end. RV, I think this would be an obvious choice for you.

The NOS Brimars are excellent too at $80 each, I have a pair, BUT it does not offer the softened top end you are looking for.

The RADIOTECHNIQUE 12AU7s: for $95 each, have not tried, but probably excellent+.

there are other NOS tubes out there. I recommend going to Upscale website, and watching the videos on each tube that they sell.

 I will soon have a credit of about $130 from Tube Depot, having already bought but not opened, a complete set of tubes for my preamp.
With this, I’m thinking of getting two Gold Lion 12AU 7’s for my line section.
This won’t cost me anything extra. If this doesn’t make much difference I’ll go to more expensive NOS tubes (of which Tube Depot has a limited supply.)
I mentioned the 6SN7GTBs as between my preamp (Schiit Freya) and my amp (Dennis Had Firebottle HO) that's all there is for non power or rectifier tubes. My previous amp used 12AX7s and 12AT7s with my preference winding up as new Gold Lions for the 12AX7s and NOS Mullards for the 12AT7s.
Pretty simple, really.  Better tubes equal better sound.

For these variants, with few exceptions, you need to look toward old production.  Not necessarily NOS, though so many aspire to that.  I found you can do VERY well for yourself buying tubes others sneer at as they come up measuring as having obviously miles on their clocks.  Old tubes often play quite a long time, and pretty much sound great until they give out.

As has been mentioned the best 12AX7 tubes are 5751.  What I can add is the best 12AU7 are 7316.  Both tubes will cost you deep in the purse.  Both tubes instantly convince you that you won't go back.

If you do want to buy new production tubes, Shuguang triple mica 12AX7B aka Silver Dragon and Psvane 12AX7 and 12AU7 stack up surprisingly well
Have tried a fair sample of the triple mica 5751 black plate tubes, as well as nos mullard 12ax7's.  Have not tried the gold lion 12ax7s, but can relate that the grant fidelity psvane 12ax7 are one fine tube.
Nos vintage tubes sound significantly better than any tube made today and they last much longer. I use Mullards, telefunken and rca 12—7’s. The rca clear tops are nice and about 12$ a tube. I don’t like nor have had good luck with modern day reissues. 
You can try swapping tubes for sure but even better is to change a few of the resistors.  Carbon film, metal, shinkoh, caddock, etc.  cheaper way to go and a lot more fun!

Happy Listening.
Yes try NOS OS 5751s they were all the rage 10 years ago.  They are more reasonable these days.  I advise you get Sylvania blackplates, RCA easier to get and even GE again blackplate and their 5 star brand.  If your up to a search the Raytheon windmill getter 5751 is very good,  Get triple mica preferred over doubles.  Sylvania's Gold Brand and RCA Command series are worth looking for. Good Luck tube rolling is a slippery can be addictive, PM me for more advice/help.
I agree with previous comments to first replace the 12AU7’s. But, substituting Gold Lion 12AU7’s will be a horizontal move; there will not be a dramatic improvement. To really open up your preamp you need to go with NOS tubes. There is so much good info on the sonic signature of NOS tubes at Joe’s Tube Lore...
and Brent Jessee’s site...

And almarg has stated an important point about the use of the 5751 variant in your CJ preamp...
Please note: The indiscriminate substitution of type 12AX7 tubes for the 5751 will seriously degrade the sonic performance of the unit.

The 5751 has lower gain, so it's recommended to stay with a 12AX7.


Based on the recommendation at Joes Tube Lore, I’m getting a pair of RCA 12 AU7 in place of the Gold Lions.  According to Joe, they should cost around $5.00. Tube Depot has them for 12x that  price, but it will cost me about the same as the credit I’m getting.

The Joe's Tube Lore posting is from 1999 from the looks of it, but I didn't read down through the pages. You'd be hard pressed to find much for $5 these days!

The 12**7 tubes last quite a long time, so it's well worth it to step up to something really nice. The Brent Jesse descriptions of the sound qualities of various tubes is very helpful and accurate. As long as the 5751 and the 12AX7's in your PV11 are quiet, I'd go for the gusto on the 12AU7's for line stage... unless, of course, your budget allows for doing them all right now.
@rvpiano, the RCA BLACKPLATES are very good tubes for a decent price. Known for their dynamic open sonics and classic tube sound. Make sure the pair are matched and tested for noise.

There are many RCA Blackplates at various prices on Tube Depot.
 Do you have a preference?

Never mind, There’s only one 12AU7 Blackplate there!
My mistake.
 Sorry for the post
I ended up ordering a matched pair of 12AU7 RCA Cleartop (side getter) tubes from Brent Jessee, raved about by both Brent Jessee and Joe’s Tube Lore, for $69/pair.
Tube Depot is way overpriced.  I’ll have to use my credit on something else.
I like the 5814a variant of the RCA Blackplate. It is more dynamic than the 12au7. The Cleartops are good if you like extended highs.

Re... the Blackplate 12AU7, the older the better. Early 1950s, low noise is best for the classic tube sound.
I would imagine RCA Cleartops would work well in a CJ due to their airy high-end.
I’m looking forward to your listening impressions of the RCA tubes in the CJ preamplifier. Curious to know how much of a difference you hear compared to your current tubes. I believe this is a good terms of venturing into the realm of recommended NOS tube rolling. The cost of the RCA tubes seem very reasonable.  Good luck.
For Classical music I use 5814 and 5751 for 12Ax7 subs .
IMO opinion RCA cleartops are too bright on strings , maybe OK
in warm pre  but 5814 are always more musical to my hears .

Are you saying that 5814 can be used as a substitute for 12AU7?
What I can add is the best 12AU7 are 7316.
And the best of these are the Amperex Bugle Boys...

A lot of 5814s around- be careful- many are not as good as even the Chinese 12AU7s (which are really fairly competent).
The 5814s and 7316s are better grade 12AU7s.

I go back and forth with the fantastic Amperex 7316s, and the equally fun CBS 5814As. These are my faves.
Thanks for the info.  If the RCA’s don’t work out, I’ll return them and try 5814’s
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 What make 5814 would you suggest?  or What to avoid?
I never had good luck with that variant. They often sounded harsh and microphonic. So I'm not the best person to ask...
I contacted Conrad-Johnson.  They sell a complete set of recommended tubes for the PV 11 for $310.
I wonder if I should go in this direction.
The Conrad-Johnson description of the tubes is as follows:
 “V1 & V2: 12AX7 MULLARD| V3: 5751ELECTRO HARMONIX | V4, V5 & V6: 12AU7 YUGOSLAVIA.”

No further description than that.
It sounds like these are new production tubes. To go in this direction would get u right back where you started.
The only upgrade path is to try NOS.