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R/E/P => R/E/P Archives => Klaus Heyne's Mic Lab => Topic started by: carloff on January 27, 2007, 04:38:08 AM

Title: Transformer in U 47
Post by: carloff on January 27, 2007, 04:38:08 AM
Wanted to ask  about differences in transformers in U 47.
I saw that most copies uses BV8 TAB funkenwerk version. Is it 30x40mm?.Looks quite similar as Neumann BV8.
I also seen opened U 47 with GN 107 transformer.It is 30x40mm
And also heard that Bill Bradley uses in his U 47 clone HAUFE version BV8, which should be almost original because I heard that HAUFE made the BV8 for Neumann under different name.But HAUFE version is only 30x20 mm
Can I ask about sonic differences?

Milan Havrda aka Boris Carloff
Title: Re: Transformer in U 47
Post by: Oliver Archut on January 27, 2007, 12:17:45 PM
Hello Milan,
Most of the small microphone manufactures use the AMI transformer BV8 which (I spec as) a direct replacement of the Neumann Bv.-08-00A. That transformer was used mostly in U47s with 200/50 Ohm output.

The BV8-style Bill Bradley uses originated with Andreas Grosser; he had them custom made at Haufe. However, Haufe never made the transformers for U47/48 -they were Neumann in-house production, and the early ones were made by Gefell for Neumann.

(One reason that) Haufe does not make that x-former anymore is because the original manufacture of the lamination does not make that particulate type anymore.

Also, the Haufe BV8 version is more related to the Fet47 output than the historic BV8.

The GN107 was made in Gefell for the first 100 U47 or so; that one has a historic German M core...

Best regards,

Title: Re: Transformer in U 47
Post by: carloff on January 28, 2007, 09:39:44 AM
Hello oliver,
thank you a lot for answer.
What do you think please about sonic relationship between M7 PVC vs Berlin M7 capsule vs K47 with GN107 vs BV-08-00A.Is some combination from some reason the best?
also can on some way using different 1
Title: Re: Transformer in U 47
Post by: Oliver Archut on January 28, 2007, 01:10:58 PM
Hello Carloff,

all GN107 x-formers I have seen were in a pretty bad state, those x-former were wound with pre WWII wire and the PVC coating has the same problem than the PVC M7, the surface is not coating the copper anymore and some of the turns have shorts, so high and low end are compromised. I rewound several GN107 and the very early ones that were also used in Gefell CMV5 bottles used sub-standard metal cores, the later UI cores (similar in size to the later BV8 core)used a different core alloy that the BV8.

The is a distinct difference in sound and for my taste I prefer the BV8.

Using different type of coupling capacitors definitely changes the sound of the mic, trying the different type of capacitors kike MP, MKT, MKS, etc. should help you to come up with the sound you like.

Title: Re: Transformer in U 47
Post by: Oliver Archut on January 28, 2007, 05:20:15 PM
Hello Klaus,

just saw that you edited my post about the x-former, I would like to get a definition established on components.

I wrote:

which is a direct replacement....

you edited:

which (I spec as) a direct replacement...

Here is my definition on components:

genuine replacement,
either NOS or in production (that is virtually unchanged)item by original manufacture,
like Neumann Berlin K47/49, Neumann Gefell M7 etc.

made by the original/historic manufacture or company that owns/license the name, 3rd party manufacture that make the item identical,
like Western Electric 300b, Telefunken USA ELA M 251, etc.

direct replacement,
an item made by a 3rd party or original subcontractor that is identical in technical specs and fits right into the application.
Hauen capsules, Wagner M7, my x-former, etc.

general replacement,

an item that fits into the technical application but is different, made by original manufacture, company that controls the name, 3rd party manufacture, etc.

Let me know if you agree....

Best regards,

Title: Re: Transformer in U 47
Post by: Klaus Heyne on January 29, 2007, 12:09:19 AM
I agree with all of your definitions, Oliver, except the one for direct replacement:

direct replacement is, you state,

 an item made by a 3rd party or original subcontractor that is identical in technical specs...

First, if the item came from the original sub contractor, it would probably fall in your category of "reissue" or "genuine replacement".

In cases where the (third party) manufacturer has no direct access to the original production facilities or know-how, the manufacturer will try to make his replacement identical in specs and sound.

You mention Haun capsules. I happen to be pretty familiar with his products. Haun makes very good capsules, some of the best in the world, right now, and he will make it the closest thing to an original capsule he can.

But I would not call his CK12 or K67 offerings direct replacements: he has no access to Neumann's diaphragm tensioning protocol, or where their Mylar is sourced and what exact sputtering technique was used. It remains a Neumann secret.

That kind of process (reverse engineering) will under no definition lead to a product with provably 'identical' performance (either in specs or aurally) to the real thing.

So, the dilemma is that if you define your transformers as "identical" to the original ones, it would need to be confirmed by an independent authority (which, of course does not exist in our field.)

When I compared your T14 -replacement to a real T14 in the same mic, it was the first and only replacement that was in this case indistinguishable from the real thing. But you know how impossible it is to make my subjective impression into an objective statement, as you define it.

How about if you just call these replacement transformers "the best alternative to an original transformer in existence today"?