As described previously the tube Guru told me that my Audio Research SP14 was designed for a Russian 6H23Pi (6N23). Back in the day the best "6DJ8s" were Russian and ARC tweaked the SP14 to work best with them. Thing was they were not 6DJ8s but a Russian tube called the 6H23 (H is the Cyrillic N) which was really really close but had different parameters. By customizing the preamp to work best with the commie tubes it did not work best with actual 6DJ8s.
My tube guru did not have a detailed design history of ARC products, but the schematics are on line. The guru looked at the schematic and went hmmm, noting the diagram and parts list specified a "Russian" 6DJ8. Russia never made that type and they were always substituting. They still made tubes as their supersonic fighter jets and nuclear bombers still used them. To be Fair the MD F4 Phantom also had tube avionics and was still in service then. The Americans just bought Russian tubes ha ha. When the CCCP collapsed an American company bought the Russian factories to feed the glass heads.
I have three go to places for vacuum glass jewelry.
The most knowledgeable is Upscale audio. The best prices have been the tube store but I check them all.
My SP14 has but one tube. When my old one needed tubes it needed 5 at a time. With one it is easier to go premium. I had bought a premium 6DJ8 Russian tube. The first one failed on arrival and Tube Store replaced it FoC. I put the replacement in my headphone amp to check it was OK and to give it some burn in. Then I forgot about it.
So Guru and I were discussing the tubes vs transistors rabbit hole. The SP14 would work OK with a 6DJ8 but is perfect for a 6N23. Further a real 6DJ8 could damage the very sophisticated circuit. Dear me!
I knew I had a Russian Tube. Upscale Audio and tube store both listed them as Electro-Harmonix 6922s gold pin. UA went further and said these were actually relabeled 6N23s. So I had the correct tube but in the wrong machine. Ha Ha Ha.
Last night I pulled the ten machine screws on the cover, yanked out the JJ6922, and put in the EH 6922/6N23. Shit what a FN difference.
Sometimes different is just different. And sometimes it is FN better, a lot better.
I did a modest warm up of the franken amp and the sp14. I was anxious to hear it. I put on the Diana Krall album I had listened to a day before. I could tell it was still warming up. DK's voice had some rough sibilance at first then the whole thing came together. Rich and deep and audio wonderfulness. I could now clearly hear her lips part as she started a phrase. The back up artists were right there. The metallic pluck of the guitar was high grade steel. The detail was amazing. And I hate to use that old golden ear chestnut but it was palpable. She was right there in my living room.
Next I threw on my 1970s copy of Paul Simon's "there goes rhyming Simon". The trick track is always "Tenderness". It was really good. My old SP12 enveloped the background singers in a huge space I loved, but the SP14 had been more modest. Read that as more accurate. Now it was more real. Then "Take me to the Mardis Gras" with great dynamics that used to upset my Shure V15 III. Here amazing and well damn good. Remember this is an original 1970s album. I take care of my stuff.
My wife needed me to turn it down. "Why always so loud" and I had a thing to do with my cycling club so I shut it down and went out.
Oh I bought this tube well before Putin decided to try and wipe out a smaller country thinking it was going to be a walk over. Ukraine is where my fathers parents were from. I have skin in the game.
