Klaus says it is not a 6S6B tube. However, it is possible with FleA and Beesneez (and others) using the 6S6B, this may have led Neumann to a similar tube.
To be fair, he said the tube in his 1st sample was similar but not a 6S6B. The tube in the next sample was different but he could not identify it so it is possible that it might be a 6S6B, at least thats how I read it. Quote below.
"Though the tube in my prototype specimen in March looked similar to a 6S6B, a Russian military type, it was not a 6S6B (Neumann did not fully rub out the label, so I could clearly identify it). That tube was changed out on the mic's second trip to Oregon. As the i.d. on the new tube was completely removed, I cannot confirm whether it’s the same or a different type that will be used in the serial M49V (see above)."
Thank you. I updated my post. Clearly, Klaus is saying the prototype was not a 6S6B. As to the tube on the "second trip" to Klaus, the only thing I can discern is that the i.d. was removed and Klaus cannot confirm if it's the same (likely meaning "same as in the prototype) or a "different type" that will actually be in the mic someone purchases from Neumann. Maybe some of you or Klaus can state more.
Yes, that whole part is weirdly-worded; I imagine on purpose.
I noticed how he said that in the prototype, what it was not, but also did not say what it was, even though he also said that he knew. It also does NOt say the second delivery or the release version is or is not a 6S6B
So, you're saying there's a chance......
The tube in Klaus Heyne's review clearly looks like a 6S6B(-V) to me, or a 6S7B theoretically. The paragraph puts so much emphasis on the prototype tube (that is not shown). That alone made me kind of suspicious. 😉 Still, he admits that the production part might be a 6S6B. I think it is. I do not see any other contenders. When I first read the passage, my gut feeling was that the whole purpose of it was to distract the reader a little. He later states “…here I agree with Neumann to keep the tube type they chose confidential…”. I would write a passage in a similar way to respect Neumann’s wish for confidentiality while avoiding to state the obvious.
RE: categorizing the AC701 as neutral or not having that much impact on the sound of the vintage Neumann's.....
My experience is pretty much the opposite. I have tried / used / owned a lot of vintage Neumann's in the studio's (I have not owned a U47 though), and my impression is that the AC701 absolutely brings an intangible to the party that cannot be understated. This mystery push to make the unidentified tube the sonic equal of an AC701 definitely leaves me suspicious. -- Kla** or no Kla**. I respect the man immensely, but too much of this smells like marketing to me. I would be SOOOOO happy to be proved wrong, but I honestly don't think so. If this new tube is the equivalent to an AC701, why have so many of the classic Neumann DOA mics not been retrofitted with this *new* tube in the past? If it's a complete match with no change of transformer or other circuitry, Neumann should be proud of their find and should be retrofitting vintage 50's, 49's, 269's, 53's, 54's, etc. with these new (old) equivalent tubes. If that question can be answered to a satisfaction, my doubts may be assuaged - a bit. Until then, I remain wishfully optimistic, but experientially cautious.
thehightenor - re: the eventual re-release to the U47 and a VF14 "replacement".... unless I'm mistaken, Kla** has already mentioned that there IS no "acceptable" replacement for the VF14 available. So that would preclude Neumann from a 47 re-release that was a legit "clone" of the original.
That or you and Klaus are really in complete agreement, the tone you love is his transparency, and you might like this tube🥸 Who knows ? When it becomes common knowledge you will have to try one. My take, first it will be interesting to see if all 49’s have capsules tensioned to Klaus’s preferred tension and if this becomes standard for K47/49 capsules. Second I think while maybe not dead on copies I think for the money we will realize the Flea is a bargain.
So your saying then the FLEA might become a Frontline prescription, for the Vets among us? Chris
Last Edit: Aug 31, 2022 15:59:11 GMT -6 by chessparov
Testing these tubes is quite simple. For us at Beesneez, we have a test unit made up that the tube legs clip straight into. We can test up to 4 tubes at a time and it takes 3-4 hours to test each batch. It sounds like a long time but it isn’t really as over the period of a week, we can easily test 100 or so tubes.
Regardless of what others are saying, Neumann absolutely are using this tube in the re-issue. Scratching off the print doesn’t make it a different tube It is a great sounding tube so I am not surprised.
In average testing, we seem to be QC passing 70 - 80% of these tubes. This is quite a high pass ratio.
If Neumann is really hand picking these tubes, how are they testing them? What is happening to the rejects? Are the rejects back out on the market? Are they soldering them into mics and listening as part of the test? If that is the case, then if someone really wants to know if their tube is as good as the one Klaus says is indistinguishable from the AC701, then it seems that it makes sense to contact Klaus.
Another option might be buying the tube from Beesneez or Flea who uses this tube in their mics. But unless they are testing the tube they are selling in a microphone, then I am not sure it is going to be on the level of the hand picked Neumann tube. And yes, Neumann may actually be selecting some tubes and rejecting others. I remember talking to a mic manufacturer about a particular tube, and it was interesting how many were rejected. I am not sure how this applies to the particular tube at issue, in terms of reject rate. As I understand from reading, even some AC701s get rejected.