AC701

[GeorgeToledo]

Imho, the most probable reason is the capsules...
Flea has its own sound and doesn't sounds like a good original vintage Neumann capsule, and even with actual Neumann production, the quality can (sadly) be hazardous ...

I don’t think it’s the capsules, because Neumann capsules sound fine and as expected when placed in known mics and circuits.

The FLEA capsule doesn’t sound like the Neumann either. But there is a sort of commonality between the way both of the russian submini M49 sound regardless. It’s mainly in what happens with louder transients, to my ear.

 

[GeorgeToledo]

So is it confirmed in the end it's 6s6b-v?

I don’t know what counts as confirmation.

The inner structure of the tube in the Neumann seems to perfectly match some 6s6b-v runs, and it seems to be a match otherwise. Comparing the inner structure was enough confirmation for me. Maybe it is some special run, I wouldn’t want to bet my life about it. I might bet a few hundred bucks on it though.

I think the reason Klaus claimed it wasn’t a 6s6b-v when he was sent a mic that still had the label on the tube, is because of course the writing on the tube wouldn’t read that way, it is in Cyrillic. Just my conclusion.

 

[tomas.borgstrom]

There’s something about the 6s6b-v in Neumann’s M49-V that sounds a very little bit aggravating. It doesn’t quite yield the same smooth sounding result as the originals. Maybe it’s some other aspect apart from the tube choice, to be fair. Though I feel a bit similarly about the FLEA mics that use the tube.

I agree, 6s6b-v is a good choice for tube microphones but the sound differs from AC701. Neumanns capsules are still among the absolute best. A vintage M49 with a new K47 sounds great, so do U67/U87 with a new K67/K87.

 

[vintagelove]

I don’t know what counts as confirmation.

The inner structure of the tube in the Neumann seems to perfectly match some 6s6b-v runs, and it seems to be a match otherwise. Comparing the inner structure was enough confirmation for me. Maybe it is some special run, I wouldn’t want to bet my life about it. I might bet a few hundred bucks on it though.

I think the reason Klaus claimed it wasn’t a 6s6b-v when he was sent a mic that still had the label on the tube, is because of course the writing on the tube wouldn’t read that way, it is in Cyrillic. Just my conclusion.

Just to be clear, when they first send him the mic, it came with a tube that he stated was not the 6s6b. But... when they sent it to him a second time, it came with a different tube. That's the one in the pictures, and he says (paraphrasing) he's not sure what it is.


I'm not a tube expert, but I also compared pics of the tube and I couldn't see any differences.


From Germanmasterworks.com

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

 

[vintagelove]

There’s something about the 6s6b-v in Neumann’s M49-V that sounds a very little bit aggravating. It doesn’t quite yield the same smooth sounding result as the originals. Maybe it’s some other aspect apart from the tube choice, to be fair. Though I feel a bit similarly about the FLEA mics that use the tube.

Also from Germanmasterworks.com


"An ever so slight (underlined!) mid-range hardness of the new tube completely disappeared when S4 was opened (up). I speculate that the difference has to do with the tube's sensitivity to slight changes in input impedance introduced by the negative feedback when S4 is closed (down)."

 

[GeorgeToledo]

I agree, 6s6b-v is a good choice for tube microphones but the sound differs from AC701. Neumanns capsules are still among the absolute best. A vintage M49 with a new K47 sounds great, so do U67/U87 with a new K67/K87.

I also don’t think it’s a bad choice for the new mics just because I think the sound is a little different. It may be the best choice, or at least a well considered one.

 

[terry setter]

So is it confirmed in the end it's 6s6b-v?

I don't believe it is a 6S6B-V. Again, I'm quoting Klause Heyne, because I haven't been inside the new M49-V yet. He says that the prototype they sent to him had a tube that looked very much like a 6S6B, but was not. Then, when they went into production, he says that Neumann changed the tube to yea another one, and that he doesn't want to announce to the world what that tube is. The article is at: Neumann M49V: Complete Tear Down and Analysis .

There are threads on the this forum discussing which sub-miniature tubes sound closest (and some would say identical) to AC701s. Oliver Archut also wrote about it. Happily, some of the best of those have 6.3V heaters.