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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.
rohitdev

Showing 11 responses by rohitdev

rohitdev OP
18 posts
 
Thank you Hifiman & Rich.

Pardon my ignorance but by EH for the
12ax7
12AU7
EL34s
6CA7s
you guys mean the electro harmonics made in russia tubes? correct? Not NOS USA or Europe.
rohitdev OP
18 posts
 
Rich,
Thank you for confirming

Hifiman,
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?
rohitdev OP
18 posts
 
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?
rohitdev OP
18 posts
 
Ok Rwwear. Stop with the links already. My thread is for hifi amps and not guitar pedals.
rohitdev OP
18 posts
 
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?
rohitdev OP
18 posts
 
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?
rohitdev OP
18 posts
 
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.
rohitdev OP
18 posts
 
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...
rohitdev OP
18 posts
 
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.
rohitdev OP
18 posts
 
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.
rohitdev OP
18 posts
 
Any updates on those 12AU7s guys?
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