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Author Topic: Neumann U47fet Reissue: Complete Tear Down and Analysis  (Read 22259 times)

klaus

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Neumann U47fet Reissue: Complete Tear Down and Analysis
« on: October 17, 2014, 06:55:00 pm »

What company can safely use the word 'reissue' for daring to name and shape a new mic after an old, without receiving ridicule, disdain, or other forms of disrespect from audio professionals and collectors? Of the remaining Heritage brands, only Neumann can!
AKG cannot, and Telefunken... well, that's an entirely different story again.

'Reissue' is the appropriate terminology for a mic that most closely resembles its direct forbear, ancestor, or whatever else you want to use to describe true blood.
In my dictionary that was assembled from a life time of experience, rather than from a Thesaurus, 'Replica' connotes a cheap version of the real thing, and 'copy' and 'clone' are more honest efforts that fall short. That leaves us with "Re-Issue"- the closest thing to the real thing, where all vital, sound-shaping components are identical with the original, and the rest as close to it as can be sourced or manufactured today- while cutting absolutely no corners in doing so.

It's been a couple of decades since Neumann "revisited the past" with considerable dedication and attention to detail: The U67 reissue was, with the exception of the head/switch assembly indeed 1:1 authentic, both in construction and sound; consequently, quite unlike other copies of famous mics attempted by mere mortals, this reissue has seen its value rise right up to where the originals have recently soared in price.

So it came to me as a surprise when I received advance notice from Neumann last week that the company was going to offer, in limited numbers, an authentic reissue of the original U47fet- a model which, during its first run, never quite caught the enthusiasm of the buying public like the U47 tube did and still does: Expectations were for something a bit closer to the famous predecessor than a stubby, single-pattern rendition with a discrete six-transistor + FET op-amp at its heart, a relatively low output, and not exactly three-dimensional subtlety of tone, sensitivity and musicality.

My aim is to analyze to what extent the fet47 reissue of the ultimate kick drum mic (tongue in cheek, and more about that later) has succeeded in rivaling the original fet47, which was last issued more than 28 years ago (start of conceptualizing: 1969, beginning of production: Spring 1972).

I am grateful to Vintage King which loaned me a sample of the new mic for a few days. I also would like to acknowledge feedback from Neumann's Martin Schneider, who added valuable additions and corrections of some historic details.

Right away, looking at the outside, the mic's first impression, build quality and adherence to original dimensions, shapes and surface treatment are impressive; though it will be rather easy for a lay person to distinguish reissue from original: the cardioid sign is upside-down on the reissue.
The basket is as sturdy with its three layers of mesh, as the original, and though the bead blasting of the housing and head surfaces is a bit coarser and shinier than in the past, it does no harm to the first impression: everything looks and feels solid and absolutely identical to the original, except for a slightly shorter thread section on the mounting arm.

Ernie Black, our webmaster, has helped me upload some high res pix, which I annotated with further comments.
(FYI: in all photos, the reissue will be shown on the left.)

P.S.: All photos in this thread are copyrighted and may only be duplicated or copied by adding " Klaus Heyne 2014".

Once you carefully look at the side-by-side pix- reissue and original- you recognize that the reissue is indeed the real thing, all the way to the muddled, point-to-point arrangement of discrete FET, capacitors, resistors and wiring-all still arranged like an enthusiastic bread board project. How an ultra-high tech company like Sennheiser could still train human beings to duplicate this mess and solder it in place, rather than use a neat SMT chip is beyond me. But duplicate they did, in every little and big detail, all the way, no shortcuts. Amazing. This fet47 reissue is even closer to the original in all aspects of parts choices, construction, build quality than the few hundred U67 that were made in 1992 were to the original U67.

Note to fakers: knowledgeable fet47 collectors will not fail to distinguish original from reissue- there are subtle nuances everywhere, and no part could ever be substituted and not noticed as stemming from the reissue- slightly different angle and bead blasting of the Philips screw heads...different mesh density of the inner top basket layer... Fairchild FET vs. TI FET...
Having said that, all parts aside of the new and hopefully longer lasting switches (see below), are fully interchangeable between old and new.

The Sound

I used two stock U47fet (circuits 930-04, 930-05) as comparison. I left the strapping at 200Ω (bottom switch at right, full output position), and also left the fairly useless attenuator switches (low-end, -10dB) off.

How does the sound of the reissue compare? Same cotton-mouthy sibilance, same restricted high- and low-end, same dynamic behavior. I could not tell the difference in sound and character signature between original and reissue, even after switching head assemblies around: the op-amp-driven processor is such a strong sound shaper, it obliterates any possible subtleness derived from different capsule timbres (and the K47 capsule, including the current batch, is quite a stunner when not pressed through so much electronic processing as it is in the fet47).

Speaking of subtlety: The fet47 has none, and never had any. But there is a clearly identifiable character to this mic, and that character has a deserved, firm place in any well-stocked mic locker: I don't need to revisit the peculiar synergy between a kick drum's beater attack, delayed drum head response and this mic. It also excels with stand-up bass, because it does not obliterate texture, and does not boom too much in the bass, it's fantastic on many a brass instrument, and even works with some voices, particularly male (the transformer and K47 add to a faint impression of a U47, despite the op-amp).

Bottom line: the U47fet reissue has the exact same sound in all its (non-) subtlety as the original. And, no wonder: all sound-shaping electronic components, capsule, FET, head shape, basket, transformer, etc. etc. are identical. with the original version. (Even if Haufe or whoever makes the transformer now cheated on the exact transformer winding specs and core laminations of the original Berlin-made transformers, they must have done an awfully good job faking it).

So here is my prediction: the sales curve for the fet47 will start steep, filling a need in the $3.5K price range for a specialty mic of highest build-quality and superb quality control, like few other mics currently can. There will also be some hoarders and collectors standing in line who hope for the same result as the U67 reissue (right before the 2008 crash, fet47s went for well above $4000.-), and, after the initial rush, sales will gradually fade. But hopefully, sales will not fade below profitability for Neumann any time soon, because it would be a shame to not entice Mr. Fraissinet towards scheming the next vintage reissue (starts with a "K" and ends with a "4").

Ernie Black, PSW's webmaster, graciously helped me upload the pictures (hence his name as poster).

First picture:
Note the shorter mic stand adaptor piece on the reissue, copied from the 1983/84 model, and also used in TLM170
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Klaus Heyne
German Masterworks
www.GermanMasterworks.com

Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #1 on: October 18, 2014, 12:45:32 pm »

Rear View.
Note the new switches are in the 'off' position mid-way, whereas the original switches had the indent at the bottom of the switch travel when 'off'.
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Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #2 on: October 18, 2014, 12:46:09 pm »

Basket Front
Note the reversed cardioid logo on the reissue. Same as on the original model manufactured from 1980 onward (original on right is from 1975 and is featured throughout this analysis).

Other than that, same quality, dimension, weight and feel as before.
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Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #3 on: October 18, 2014, 12:46:48 pm »

Basket Inside
Inside weave on top screen is the finer mesh variety, as used in the model after 1980, but, unlike the M149, the basket is still a three-mesh affair with, from outside: coarse, fine, medium.

Note the different head assembly mounting surface: rather than honing out the brass plate except for the ears containing the three mounting holes (through 1980) the whole ring is now of uniform thickness, as it was after 1980.
I tried the new basket on the old head assembly, and vice versa: no problem, perfect fit.
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Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #4 on: October 18, 2014, 12:47:20 pm »

Capsule and Mount
Note the '14.' inscribed on the diaphragm ring: it indicates a 2014 capsule manufacturing date.

The capsule suspension rubber is as flexible inside the capsule column as it was before, for good damping, and nice whip-lash injuries when you drop the mic.

Hence the protective nylon capsule collar which was not part of the original, at least not on the capsules of the first two generations. The collar buffers and isolates the diaphragm ring against diaphragm distortion after an impact against the inside of the basket during whiplash: the nylon ring, not the diaphragm ring, makes first contact and redirects the impact force to the backplate, via the two collar mounting screws.
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Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #5 on: October 18, 2014, 12:47:50 pm »

Connector Plate
Aside of using a Neutrik, rather than Switchcraft 3-pin XLR, all seems the same as before.
Note the serial number of one of the first units shipped: 10106. I.e. most likely the pre-series went to <10100 or so, and they started shipping with ser. no. 10100 to customers last week.
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Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #6 on: October 18, 2014, 12:48:22 pm »

Head Connectors
Note the close resemblence of the new part to the old. We are starting at ca. 10.000 with the re-issue, (the head plate serial number always used to hover around the serial number of the mic).
The U47fet reissue most likely started at 10.100.
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Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #7 on: October 18, 2014, 12:48:52 pm »

Bottom Board
Point-to-point, as always; no chips or multipoint wire connectors to be found anywhere
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Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #8 on: October 18, 2014, 12:49:17 pm »

Amp Guts.
According to Neumann's Schneider, the model they chose to duplicate 1:1 for physical circuit layout was from ca. 1972- Circuit #02. While the electrical circuit and physical features of the mic resemble that of the #06 variety (last version with three switches. Two remaining versions, #07, #08 did away with the -6dB switch, and had the transformer output strapping permanently set for 200Ω, i.e. secondaries connected in series).

Notice the same point-to point mess that has tripped up countless repair people over the years. The version after 1974 at least had a board which you could slide forward for better access to most of the amp components (see vertical edge of the gray sub-board, with T2 (BC212) showing horizontally). Until 1974, as in the reissue, every time you want to work on the mic amp, you have to do micro-surgery in situ, due to the lack of a circuit board that can slide out.

Note hexagonal column-construction of the amp compartment of the reissue, same as the original through 1974; whereas plastic injection molding was used after 1974 to form the amp cavity (the original in all pictures is a 1975 model). The plastic mold allowed for a slot to insert a newly developed rectangular circuit board, which made component layout and servicing a bit easier.

It's kind of amazing that Neumann would succumb to such unorderly component layout, but kind of cool that they have no shame doing it, for the sake of keeping it all original and immune from criticism by "100% authentic"-freaks, damn the preconception of German anal-retentiveness.

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Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #9 on: October 18, 2014, 12:49:42 pm »

Transformer Side
Note transformer core lamination differences. This could just be the appearance of the cutting edges of each laminate, or it could be a different alloy. Winding resistance seems similar to the old one, 10%. In any case, it does not seem to matter- the tone of the new mic retains its original characteristics.
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Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #10 on: October 18, 2014, 12:50:11 pm »

Top Board plus new FET used.
Late versions of the original (after circuit 930-05) had the FET mounted as it is on the reissue: on the outside of the top board (mine is a 930-05). Note the new FET used: a Fairchild 2N3819, same model, different manufacturer, as was used until the early 1980s. Sample FET placed on top of board, for illustration what it looks like.
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Ernie Black

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #11 on: October 18, 2014, 12:50:42 pm »

Switches.
The question has come up repeatedly: can the old attenuator and impedance switches, which tended to self-destruct, because of their brittle plastic housings, be replaced by the switches from the reissue?

The answer: not easily, if at all. The mounting hole distance to screw them into the side and bottom wall was 22mm old, and is 17mm on the reissue. With other words, the original fet47 mic housing and frame would need to be modified to fit them.
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hasbeen

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #12 on: October 18, 2014, 02:18:41 pm »

Thanks for taking the time! Can't wait for sound impressions.
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musicalnyc

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #13 on: October 20, 2014, 04:14:48 pm »

Awesome.  If only every microphone review on the internet were this deeply knowledgable, thorough, and helpful...  Thanks Klaus! :D
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Glenn Bucci

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Re: Neumann U47fet Reissue: Complete Tear Down and Analysis
« Reply #14 on: October 21, 2014, 07:16:30 pm »

Cheers Klaus, your insight is always appreciated and insightful.  ;D
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