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A higher level than Mullard in tube quality?

I am just getting started in tube rolling which I find pretty exciting. Any thoughts or comments would be appreciated.

I have been upgrading the pre-amp tubes in a DK Design Mark II intergrated amp. My speakers are modded Magnepan 3.6's. My source is a Resolution Audio Opus 21. I listen to mostly acoustic jazz and vocals.

I went from a set of Electro-harmonix 6922 (like $20 each) to used 6dj8 Amprex "Bugle Boy" ($40 each) and that was a nice improvement -- well worth the cost. I just upgraded to Mullard 6922 NOS ($90 each) and WOW! I am amazed at the improvement. I could not have imagine that I could improve a $10,000 rig so much for so little. Now I am thinking ... what's next? Can I spend $300 and get another step up?

At this point, what is my next level up? Or is it more sideways to different type of sounds?

Question: used tubes of the same vintage are significantly less than NOS. Is there any down side to buying used (but tested) tubes? I can get 2 for the price of one NOS and probably get more hours from 2 combined. Also, it seems like a good way to lower the cost of testing different types of tubes ... or ... does the aging change the sound.

Question: I have Mullard Blackburn plant made 6922/E88CC gold pins in GE label from the 1960's. Would I get a different sound if I bought different Mullards, such as from a different time or a different plant? And do I just have to take the dealers word for the details -- it all seems so vague.

Right now I have $300 burning a hole in my pocket to try the next step up. But I fear I may hit the diminishing return ...

Thanks for your comments
mcmanus
scorpio1951
189 posts
 
  These are all really great posts. I learned much about tubes when I re-tubed my McIntosh MR-71 tuner last fall. I went with NOS Telefunkens, all made in the 1950's and 1960's. At the same time, I also changed the cheap Chinese made tubes in my McIntosh MC2300 tube preamplifier with NOS Telefunkens. The sound improvement in both components was fabulous. I deliberately did not buy used tubes, as I think you may be buying shorter tube life and possible reliability problems. Most of the time, you get what you pay for.
bdp24's avatar
bdp24
9,788 posts
 
When I spoke with Tim de Paravicini (EAR-Yoshino designer) at the 2015 Newport Show, he told me the old Mullards were his favorite tube brand. I don't know whether or not he does his designing with Mullard tubes installed in his circuits.
gryphongryph
372 posts
 
Have the same DK Design amp, and I also like the Mullard the best, have tried a few others, but with the Mullard, the amp made a wonderful midrange.
have not tried the Siemens.

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rodman99999
6,128 posts
 
Also of note, just like the various CCa iterations(ie: late 50’s-early 60’s, Siemens CCa with grey shield and external date code vs later silver shield, w/internal date), there are less desirable(not quite as wonderful) 6N23Ps out there. For instance, the 1975, grey shield, Voskhod Rockets(Kaluga factory), has joined the ranks of, Holy Grail/unobtainium in NOS/sell your firstborn to get a pair, pieces out there. Seems these got very popular a few years back and there was a run on them(and rightly so).
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