Neumann M49V tube mistery...

[kingkorg]

6s7b is also a higher gain tube, so probably more THD.

 

[soapfoot]

Klaus has said that he knows the tube type, and it's not a 6S6B. I'm not sure he'd have any incentive to mislead on that point.

For the record, I also inquired about his relationship with the project and Neumann/Sennheiser for the sake of transparency. He stated publicly in response that he had to return both review units and received no compensation other than the ability to order a new specimen at his usual dealer cost.

 

[kingkorg]

Well, it could still be 6s6b-V. I am not concerned about his direct financial benefits from the Sennheiser/Neumann.

 

[mrbutterskin]

Are there, though? I'm not aware of any with the same structure and lead arrangement. Do you have any models to list? Would genuinely like to know about them

There are others closely, very closely related tubes to 6s6b.

 

[klausheyne]

What I don't understand, and maybe Mr. Heyne can explain it to me, why he wired the grid connection from the AC701 all they way down to the PCB pad and not directly to the insulated standoff right next to it?


Photo:© Klaus Heyne, 2022

Fair question. I wired it that way, for two reasons.

1. At worst, the extra length added to an already longer than usual ultra-high impedance path between the tube's grid wire and the stand-off post would have shown up in noise or artifacts. It did not.

2. But a direct connection between AC701 grid and stand-off post, completely eliminating even the current path length, may have influenced the comparison. To make sure, I did that, too, and again could not hear or measure a difference. So I decided to duplicate as much as possible the grid pathing in the M49V.

 

[klausheyne]

Well, it could still be 6s6b-V. I am not concerned about his direct financial benefits from the Sennheiser/Neumann. There are others closely, very closely related tubes to 6s6b.

It was not any version of a 6S6B. I honestly do not know the tube in the final series.

 

[vintagelove]

Well, if some people know, it’s out there. Some folks just need to put their heads together and investigate. If anyone is interested, here is a catalog, triodes start on page 80. A few things will help narrow it down (I know you guys know this, but I mention it because it’s right at the top of each tube descriptio), filament voltage 6.3 and heater current 200ma to start. Feel free to add stuff we might look for... Sure would help if someone read Russian (so much for the Russian I took in high school).

http://www.tubebooks.org/Books/Atwood/Katsnelson%20&%20Larionov%201981%20Receiving%20Tubes.pdf

 

[k brown]

My 2cents - a little too much obsession with the tube; as Decca found out decades ago, the transformer in the M49 and M50 has waaay more to do with the sound than the tube. When Decca replaced the tubes with a simple FET circuit, they found the change in sound insignificant.

So, the big question about these new '49s is, have they been able to come up with a transformer that can come anywhere near the big, big sound of the original?

 

[Khron]

What's so "sci-fi" or irreproducible about the original transformer, though? Surely they have all the core & winding data they'd need...

 

[k brown]

One would think - that transformer is talked about in hushed tones like we'll never see the like again (?).

 

[vintagelove]

From KH review


"I was assured by Martin that the transformer is identical in its specifications to the original BV11."

 

[kingkorg]

My 2cents - a little too much obsession with the tube; as Decca found out decades ago, the transformer in the M49 and M50 has waaay more to do with the sound than the tube. When Decca replaced the tubes with a simple FET circuit, they found the change in sound insignificant.

So, the big question about these new '49s is, have they been able to come up with a transformer that can come anywhere near the big, big sound of the original?

I agree, so many good tubes out there. The only reason i'm interested is because the price of 6s6b, one of my favorites, might go balistic. But i just re-stocked at regular price, so whatever...

 

[Purplenoise]

I agree, so many good tubes out there. The only reason i'm interested is because the price of 6s6b, one of my favorites, might go balistic. But i just re-stocked at regular price, so whatever...

It might not though, there are way more 6s6bś out there than ac701s and it seems 6s6b has a lot less rejection rate. Also the m49v looks like it will be produced in limited quantities ( which I think it’s part of the hype since it’s not really that hard for produce considering it’s pcb…the u67 or 87 are way more complicated to produce)

 

[kingkorg]

Well, that's what i thought before i went for a search some days ago. Russia-Ukraine situation doesn't help, and at least on eBay the stock is substantially reduced.

 

[Purplenoise]

Well, that's what i thought before i went for a search some days ago. Russia-Ukraine situation doesn't help, and at least on eBay the stock is substantially reduced.

I think it has been like that since the war started . Now you can only get them mostly from Ukraine and Boulgaria.

 

[Moby]

What's so "sci-fi" or irreproducible about the original transformer, though? Surely they have all the core & winding data they'd need...

Probably the core alloy is not the same as the vintage Bv.11. So, generally speaking, ratio, inductance, DCR and capacitance can be "to the spec's", but it's hard to replicate the magnetics resistance of the alloy.

 

[kingkorg]

Probably worth to mention for the less experienced readers that some of these differences in performance of different components will be virtually inaudible, and easly adjusted with eq...
Noise and thd will probably be dominated by ambient noise, gear in the chain that follows...

-1db at 30hz, vs 10hz...

Mic placement and other basic stuff will be always more important.

Some of the differences might show up under extreme conditions in which these mics are rarely used. We are talking about 1% of differences, sometimes just educated guessing, theory.

 

[granger.frederic]

It was not any version of a 6S6B. I honestly do not know the tube in the final series.

Interesting...
With the 6S6B-V, I noticed two issues : a bit too hot in a mic, and a bit too high grid current/leakage which drops the low end.
By the way, if the mistery M49V tube is as hot as the 6S6B-V, i wouldn't mount the cathode ecap as close as it is in the pre-version, for long term lifespan considerations.

 

[bremusound]

The 6s6b-v takes 200mA of filament current which is exactly what Neumann wrote about the tube they used.
Agreed about the el cap placement!

 

[Gus]

The following is meant in a positive way IF the pictures in this thread are representative of the production units.

The microphone looks nice and I would assume sounds very good.

For the price I would think it would be detailed like a high end cars interior, exterior, air vent slots, tires, wheels, under the hood etc.

People will take pictures of the inside and post them on the web. If you look around the web you can find pictures of the interior of microphones.

Inside PCB picture
How the resistor leads are bent (cosmetic)
electro cap touching the tube(heat) others posted about this
Why does the grid wire attach at the PCB?
Flux on the PCB Is it "no clean flux"?
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