12ax7 12AU7 EL34 / KT 88/ 6550 upgrades for PL2

I acquired a used primaluna prologue two a month or so ago. This is my first experience with tube amp. Coming from rotel amplification I am just wowed with the tubes. The PL2 had upgraded tung sol 6550s. Nice sound. But I changed to new issue Electro Harmonix H EL34EH. Ran-in the tubes two days straight with music. Was simply blown away with soundstage and tone! Guitar riffs and blues sound gorgeous! Bass isn't too shabby either. Quite enjoyable.

Then found a little more improvement by switching 12ax7s from stock to Electro Harmonix ($10 bucks each).

The tried changing out 12AU7 with some old used tunsol 5963/12au7 (made in the USA) and was not happy. Changed back to stock.

Does anybody have any good experiences with upgrading the 12ax7/12au7 and power tubes on the PL2. I would appreciate the advise. Tube rolling is so much fun!

My speakers are quad 22L2, cd player oppo bdp 83se and analog source is MMF5 w/ MMshure ML140E.
I do not have experience with your gear, but have found Electro-Harmonix 12AU7s to work very well in my heavily modified conrad johnson PV12L. Previous to them, I had been using NOS tubes which had a warmer timbre but they became noisy quickly. At $90/pair it was too much $ for the sound. The EH tubes have a more linear sound across the frequency spectrum and like the Energizer bunny just go on and on. I was much more successful tuning my system with Herbie's tenderfeet than with endlessly rolling tubes.

I have owned the PL2 & PL5 for 5 years.

After experimenting with SED Winged C KT 88s & 6550s for the power tubes and NOS Mullard & Sylvania 12AX7 & 12AU7 for preamp tubes, I settled on Electro Harmonix EL34s & 6CA7s for the power tubes and Electro Harmonix for the preamp tubes.

I found that I got the sound I liked best with the EH's. The speakers are Totem Mites & Opera Plateas.

Thank you Hifiman & Rich.

Pardon my ignorance but by EH for the
you guys mean the electro harmonics made in russia tubes? correct? Not NOS USA or Europe.
Correct ... new production EH tubes made in Russia.

Thank you for confirming

Thanks for the Herbiefeet idea. I will definitely look into that.

can anybody else share their experience with PL2 tuberolling?

has anybody tried the sovtek 12ax7 lps?
I use mullards for the 12ax and rca cleartops for the 12au tubes and new sensor mullard EL34's for the output tubes.
i've a prima luna prologue 2 using shuguang black treasure kt88z (grade B tubes), sylvania 5751 3 mica black plate and rca clear top. Speakers are proac response d1.

sylvanias and rca clear tops sound more linear and transparent which mix well with the smooth and extremely liquid sounding black treasure kt88z.

Previously i was using sed c wing kt88. It's dynamic with razor sharp focus and pin point imaging but can be quite fatiguing when paired up with the sylvanias and clear tops.

I didnt like sed 6550C or sovtek kt88. Not enough oomph rather flat. They didnt draw out the emotion as much as the sed c wing kt88 or the black treasures.

Other tubes i've tried are full music 12ax7 and create audio 12ax7/12au7.

NOS preamp tubes still sound much better than modern tubes.

My humble opinions....
oh yes, herbie labs ultra sonic rx tube rings for the preamp tubes. much much more extension from the top to the bottom. strongly recommended.

for my case, it didnt kill the "airy sound" of the tubes.
Horchai - Thank you. The Shuguang Treasure KT88-Zs look gorgeous! Are they the black treasures you have? There are pictures of them at tubestore.com. At ~ $480 for a matched quad they are quite expensive for my standards. Are they worth the sound? Other than being incredibly liquid are they transparent? how do the mids, treble and bass sound?
Ok Rwwear. Stop with the links already. My thread is for hifi amps and not guitar pedals.
I would get NOS GEC KT88, thats what I did and stop rolling after.

You want punch and musicality at the same time, KT88 are your choice, other than that, EL34 Tesla's are my second one.


6550 TUNG SOLS BLACK SMOOTH PLATES, very expensive and I would choose GEC KT88 anytime instead, but they do sound very good and build to last.

EL34 NOS TESLA ( NOT JJ ) - Very good value, recommended.

6550 NOS SYLVANIA - Nothing special, nice sounding.

To me, driving and input tubes make as much difference as the output.


12AU7 - Telefunkens Smooth plated, Brimars long plated square getters, Tung Sols Black coated glass and Mullards from the 50's, which I end up with.

12AX7 - Tungsram, Tungsols and CV4004 Mullards, which I ended up with to.

The other one I would recommend is E83CC NOS Tesla, simply one of the best sounding up there. They are identical to E83CC Telefunkens, which are such expensive that these Tesla's are just an bargain. Dont miss up with other E83CC they try to sell, cos only Teles and Teslas are the ones to get, but be carefull with your source choice, cos fakes are there.
I have a prologue 6. The 12AX7's are too good to swap. NOS RCA 12AU7's will upgrade the sound, and I found Tung Sol EL34's to work for me.
Were the 12AX7's that you swapped out, Shuguang. I found them to better than the new tubes I tried.
Orpheus10 - The 12AX7 I swapped were stock primaluna for the cheap EH 12ax7s. I am not sure they are shuguang. Are they? I found the EH 12ax7s to be marginally better but better ... in terms of bass response. Are the NOS RCA 12AU7's clear top?
Yes, they are the best bargain in NOS tubes. I get mine from Brent Jesse. I got my Primaluna new and swapped out the 12AX7's for new tubes but liked the tubes already in better. Call Upscale Audio at 909-931-9686, they can identify which tubes you have.
Thanks Orpheus10. I did call upscale and was told the pre tubes are shuguangs. I was advised to go for the mullard platinum cv4004's.
Does anybody have experience with mullard gold or platinum cv4004's usina a primaluna? any sonic difference between gold or platinum?
I am currently using SED "winged" 6550Cs, along with NOS Pope 12ax7, and stock 12au7. The Popes are absolutely fantastic if you can find them. Mine were purchased from Upscale Audio. I do prefer the sound of the KT88 over the SED 6550s. Like another person said here, I find it to sound a bit flat and dynamically constrained, but it does sound extremely smooth. Just depends on what you're after.

I am looking to upgrade from my stock 12au7s. I was told by Kevin at Upscale that the 12au7s are just buffer tubes in the PL2, and that the 12ax7's should be upgraded first. I've already got that covered, so I'd like to go for some better 12au7s.
Jwglista - I agree with you on the 6550s sounding a bit flat and dynamically constrained. I personally like the electro-harmonix EL34 to my tung-sol 6550 reissues. What KT88s have you tried?
Now the pope 12ax7 .. .are they the same as the dutch amperex bugle boys? how would you describe the change in sound from stock? I tried swapping the stock shuguang 12au7s to NOS tungsol 5963. Didnt find any improvement. Infact I liked the stock 12AU7 better.
I've only tried the stock KT88s so far. I'd like to go for some Gold Lion KT88s eventually, but I've read that some people have reliability issues with them.

I'm not sure if the Popes are the same as the dutch amperex tubes. Adding the Popes added much more dimensionality to the sound, along with a smoother and more detailed presentation. A definite upgrade over the stock tubes, and it isn't subtle either.

What you've said about the 12au7's has me reconsidering upgrading those tubes. I was going to go for some NOS Radiotechnique 12AU7/6189, but not sure that it's going to be worth the money.
I don't have the same amp, but the gold lion KT88s sounded the same if not better than either the original RCA 6550 or Genelex GEC KT88 or original Sylvania 6550 I have tried. The gold lions are expensive ($200 a quad) and I run my amps 6-8 hours a day so I am going to try the tungsol reissues next ($110 a quad).

I also found that the original telefunken 12ax7s in my preamps sound extremely good.

The bottom line is I would go with original small tubes and reissue kt88/6550 based on my experience.
yes jwglista, i am getting skeptical of the value we can find sonically in upgrading the 12au7 tubes. I have always been thinking of the reissue gold lion KT88s in favor of the shuguang kt88 z since the price is nearly half!

evilfij - I have the tungsol 6550 reissues and like them. The Electro-harmonix EL34s though are more exciting in the mids than the tungsol 6550 reissues in the primaluna prologue 2.

Currently running in the new mullard 12ax7s. They sang for an hour or so last night and already sound promising...
I am loving the new mullard 12ax7s. Kevin's advice was right on. Smooth organic sound yet the bass is full and less bloated than before. Seems like the noise floor went down and there is more detail. I bet the NOS mullard cv4004 may have been better. But am satisfied for the $ / sonics value of the new mullard.
I just got my Shuguang KT88z treasures Grade A. Thanks Horchai for the suggestion. They sound so well balanced and full bodied right out of the box! I have read that it just gets better. But recommended burn in is 300 hours?!! I bought these from the tubestore. The guys are awesome. Such a pleasure to deal with the people there. Tried to buy these treasures from grant fidelity initially but they said it wouldnt be here by Xmas. That was just ridiculuous. I ordered mine on 12/13 and I got it on 12/14. Oh well not my loss. I am just going to enjoy the music.
Any views on the Shuangung Psvanne tubes the 12AUX7 , imported by Grant Fidelity? I have been thinking about them for my amp, thanks
Love the Telefunken 12au7 ribbed plate in my VAC Sig MKIIa. It's high resolution, detailed, clear, high end extension ... just awesome. The smooth plate is too warm for me.

Also have success with Telefunken 12ax7 ribbed plate in a McIntosh MC2200. The stock Chinese tubes are JUNK and can't believe the improvements with the Tele.

Love the Shuangung BT CV181-Z in my MW Transporter so also curious about the Shuangung Psvanne 12au7.
Go with the Genalex Gold Lions. It's a new standard for tubes. They are quite wonderful.
I just purchased 2 matched sets of the Psvane 12AU7s from Grant Fidelity and got them installed today in my Cary SLP 03. My Cary 120S amp will be delivered Monday from Cary. I sent it in to get the MK 2 revision. It has all Shuangung Treasures in it (KT88 & CV181-Z) which are broken in with about 400 Hrs. on them. It should be interesting and I will post an update ASAP. The Psvanes are replacing TJ Full Music 12AU7s because one tube got loud. The sound was good but reliability is important to me. I am gonna sell the 3 TJ's cheap if interested.
I just ordered some Pavane 12AU7's from Grant Fidelity. The notice says they shipped the same afternoon I ordered. I also purchased 300b's last year - weren't cheap but again service was excellent. Looking forward to putting the 12AU7's in my preamp. Also have some genalex gold lions (6922) coming from the Tube Store - have found their service to be excellent as well. I think we are lucky to have so many excellent sources for tubes.
Any updates on those 12AU7s guys?
I have had the Amp (Cary120S Mk2) back from Cary for about three weeks now. The improvements are clearly audible and very pleasant. My impressions so far would be that the upper end is a tad bit leaner (by no means dry) with a tremendous amount of air surrounding instruments such as cymbals, bells and triangles. A cleaner, deeper view into the soundstage. Dialog has been improved to the point that you can almost see the expressions on the singers face as they finish there lyrics, a greater understanding of the music. The Amp now has 28 db of gain and is very easy to drive. The magic in the Midrange and Bass has been improved also. Female vocals and Piano are stunning!
My only regret is that I can't tell you how much the Amp revision or the Psvane 12AU7 tubes contributed to the improved sonic quality.
I was listening to an old Richard Goode (Who I had the pleasure of attending one of his concerts in Carnigie Hall) CD of Beethoven Piano Sonatas a couple of days ago and the Wife asked who it was? She said the piano sounded very nice, like a real piano in the front room. That blew me away as she very seldom comments on any thing I play except to say "Turn it Down!"
My system consists of Harbeth Compact 7 ES3 speakers, Cary Preamp SLP03 and Cary Amp 120S Mk2, and a Sony XA5400ES SACD with Harmonic Tech. Magic speaker and interconnect cables.
As mentioned above the Amp has KT88 and CV181-Z Shuangung Treasures and the Preamp uses Shuangung Psvane 12AU7s.
If I get good life out of the Psvane tubes (yet to be seen) I will continue using them and as of now can recommend them highly. Dave
I am reclining in my listening room thoroughly enjoying The Rite of Spring due in no small measure to the Psvane 12AU7 Reference Vacuum tubes. I just recently purchased these new production tubes manufactured under tight tolerances in the Shuguang tube facility in China. The Psvanes replaced gold pin EH 12AU7s. The EHs were good sounding tubes in my heavily modified cj tube line stage. The Psvane's bring a whole new "sophistication" to all aspects of sound. Most notable is a complete lack of "glassiness" in the upper midrange and treble, a smoothness to the musical texture without any loss in detail. The soundstage is open and natural. Bass is powerful and tight. These tubes are very quiet, a characteristic missing in my trials with NOS Mullards. Yes, they were warm and "musical" but the several pairs I used were always noisy...losing their vacuum?

I purchased the matched pair with gold pins for $83 including shipping from Grant Fidelity located in Canada.