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Author Topic: U47a (Gotham audio)  (Read 10219 times)

Klaus Heyne

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Re: U47a (Gotham audio)
« Reply #15 on: January 08, 2009, 04:52:58 pm »

The writing on the transformer's top, inside a U47 short body, is visible when you push the tube out of the way, and will be: "BV No. GN 8"  or "BV No. GN8b".

The latter is the one to watch out for, if you don't want the low-output model.

If you look at the wire visible as the outer layer of the two half-transformers, you can also confirm which transformer you have: the secondary windings of the BV No. GN8b are made with really thick copper-colored wiring, compared to the hair-thin wire of the original BV8.
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Klaus Heyne
German Masterworks
www.GermanMasterworks.com

Helicopter

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Re: U47a (Gotham audio)
« Reply #16 on: January 08, 2009, 06:29:28 pm »

OK, I see. Thanks a lot Klaus.

K.
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Edvaard

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Re: U47a (Gotham audio)
« Reply #17 on: October 02, 2010, 04:00:47 pm »


Hello,

Sorry to drag this thread up again but I have an associate who has suddenly got the bug to get a U47 or U48, and is asking me for advice regarding the 'most authentic' for what era, etc.

To the issue of Gotham's U47a with the BV8b transformer:

Klaus Heyne wrote on Thu, 04 December 2008 02:04

1. Installed an h-pad resistor network in front of the XLR of U.S. delivery Gotham power supplies  (down a good 6-8 dB)  then

2. added the BV8b transformer to the mic (another 6dB down); pair that with the (medium low output) stock M7 capsule, and you had an s/n disaster which virtually obliterated the dynamic impact and robust character of the mic.


Terry asked, but no one answered directly; can the transformer be replaced with, say, an AMI BV8 and the PSU resistor network be properly removed? If so, would that now make it an 'authentic' and 'proper' U47 in all regards? One U47a I saw recently was available with the kk47 assembly; would there be any further considerations vs. the M7 capsule as spoken of in Klaus's post?

I know that Oliver said "if you have a working x-former be happy with it", but after reading all the downside of Gotham's modification and knowing how much authenticity of the sound (as relates to classic/historical recordings) people are looking for in a U47, it's hard to be happy with a working BV8b! Especially for the still high price of the Gotham-altered U47.

If doable, I know that all the above would not be 'cheap' but I would then be able to at least get an idea of the cost involved.

So then another factor in deciding whether to take that approach or rather wait until a 'proper' U47/48 (non-"a" version) comes up for sale is: in the US, how much more or less common is the U47a vs. a regular U47?

If I have rough estimates of costs to compare, and the relative rarity of one as compared to the other, I can then have some reasonably defined alternatives from which to choose.



Any knowledgeable responses to the questions above would be highly and gratefully appreciated here.  

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Klaus Heyne

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Re: Neumann U47a (w/Gotham Audio mod)
« Reply #18 on: October 02, 2010, 06:47:37 pm »

1. From serial number calculations I estimate that at most 5%-7% of all U47 had a BV8b, and ca. 20% of U48 did.

2. I use Oliver's transformers in some of my work, and found them to be very good so far. I tested his copy of a BV8 (old style, full output) and found its sound to be close to that of a real Neumann transformer. (Or to be honest: I could not tell the difference the one time I tested his version.)

So using a good aftermarket transformer may be more an issue of "authentic" and "period correct" than necessarily one of sounding correct. Such a mod will of course no longer make the U47a authentic.

But in the case of that particular aberration of an ingenius mic design, it may not be a weight on the collectible value, as long as you keep the original transformer handy, in case the next owner desires an authentic collectible item rather than a good sounding microphone.
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Klaus Heyne
German Masterworks
www.GermanMasterworks.com

Edvaard

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Re: U47a (Gotham audio)
« Reply #19 on: October 02, 2010, 07:33:31 pm »


Thank you very much Klaus.


I was already leaning towards "wait for the real thing" and your clarifications and information on the relatively small number of "a" versions (especially) make it an easier decision.

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New Orleans Steve

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Re: U47a (Gotham audio)
« Reply #20 on: October 07, 2010, 02:19:03 am »

  I read this thread with little more than passing interest. I don't own or even realistically aspire to own a U47 at this point, But just love the discussion as this knowledge is so rarefied I feel privileged to be a party to the conversation.

 Do I have this correct? That All Gotham (and hence all U.S.) U47s have this "a" designation and the lower output?

 Would it then be safe to say, that all the major studios U47 inventory were these? Like at Capitol records? And Frank Sinatra?

 Thanks, Steve Daffner

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Klaus Heyne

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Re: U47a (Gotham audio)
« Reply #21 on: October 07, 2010, 01:34:27 pm »

No, you misunderstood. Very few  U47/48 came with this transformer.

After Stephen Temmer, the Austrian impresario, started Gotham Audio with some of his friends, he convinced Neumann that he was the man to re-ignite sales momentum in the countries for which he negotiated exclusive representation: Canada and USA.
He immediately drove hard bargains with Neumann, and one of them was, that all mics delivered to his territory would need to be much lower in output, to better match the input sensitivity of antiquated stateside mixing consoles, hence, increase sales.

Initially, Neumann complied by simply switching its strappable outputs to 50 Ohms (-5dB to -6dB). But somehow, after a couple of years started to wind a special BV8 transformer exclusively for U.S. export: the BV8b. That shaved another 6dB off the output.

That damage was done very late in the life of the U47/48  (see my percentage estimates, how many mics were affected, in an earlier post of this thread.)
By that time, Capitol, etc. had probably already a full contingent of mics without the dreaded transformer, so chances are very slim that your favourite Sinatra records made between 1960, when the transformer first showed up, and 1962, when production of the U47/48 by and large ceased, would have used such mic (besides, by that time, Sinatra had switched to AKG's ELA M251 and various other mics).
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Klaus Heyne
German Masterworks
www.GermanMasterworks.com
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