wa 47

[gyraf]

why would you put a brass CK12 in a U47?

We got them like that, were ex-broadcast. Used them like that for years, only recently had a factory-back-conversion done in Berlin.

The magical vf14 was used due to convenient operating voltage, not because it was special. It was readily available tube used in radios.

Actually, I'm pretty sure the VF14 was specified by Neumann for mic use - and there was a very limited amount ever produced. Only something like two or three production runs total, IIRC.
The rumor that it was a common tube comes from the fact that some category of factory rejects were at the time used in an external UHF-band extender for television tuners. I've never seen it used anywhere else.

/Jakob E.

edit/source: TFK Steel Tubes - Tab-Funkenwerk

Built from 1946 to 1957 in three production runs totaling about 27500 total pieces, it was originally developed as an impedance converter for the Telefunken distributed U47 microphone

 

[tomas.borgstrom]

Actually, I'm pretty sure the VF14 was specified by Neumann for mic use - and there was a very limited amount ever produced. Only something like two or three production runs total, IIRC.
The rumor that it was a common tube comes from the fact that some category of factory rejects were at the time used in an external UHF-band extender for television tuners. I've never seen it used anywhere else.

/Jakob E.

edit/source: TFK Steel Tubes - Tab-Funkenwerk

That's the info I've read several times as well. I've actually come across four VF14 that came from some sort of test equipment. I've also read that a some were used in radios that could be connected to the DC power lines without a transformer. I think those are very rare.

 

[tomas.borgstrom]

Guys, with all due respect i don't think you realize what goes into this kind of manufacturing, and what kind of tolerances we are talking about. I don't think you realize how frequency response and other measurements were conducted back in the day. Just look at component variances from the period. Of course those could be selected carefully.

M7 design was pretty much something they had just figured out, and no matter how big emotional response these mics bring today, by modern standards technoques used back then are stone age. The very proof of this is the fact Neumann moved on to k47 and gave up on pvc. You are aware how PVC film was manufactured back then?

Backplates are also all over the place. So many poeple who recreate these have measured the dimensions, and variations are present from hole to hole, not to mention capsule to capsule. Today drill bit wear is compensated by the machine, there was no such thing back then, and it's obvious.

The magical vf14 was used due to convenient operating voltage, not because it was special. It was readily available tube used in radios.

U47 is a masterpiece, historical piece of art. But i prefer keeping things real. What i'm talking about is reported my many knowledgeable people during the years.

Mentioning those large broadcasters, you are aware of the fidelity and quality of the signal that was broadcasted, and how it was reproduced at home? Large hi fi 30-20000hz devices? Audio band pretty much ended at 10.000hz, take a look at Neumann's pattents and see what they regard as audible range.

You're right, I don't have don't have any insight about their tolerances or how Neumann made their measurements. Any references were we can read more about it?

I don't understand what you mean with "just figured it out"? M7 was released 1932, I guess WW2 had a quite substantial impact on the continuity of their work but it had been around for many years when they produced it for U47.

This discussion is becoming a bit polarized. I know about the imperfections of tubes and capsules. I will try to find some time to record a couple of U47 and U48 with the same capsule so people can hear and decide for themselves. I'd love do the same with a couple of different new Neumann Berlin M7 but that's unfortunately not possible.

Does anyone know how predictable the sound of the respected U47-clones with M7 are (Wagner, Wunder, Flea, Telefunken USA etc)? I've heard a couple of Flea, two side by side. To my ears they sound the same.

 

[kingkorg]

We got them like that, were ex-broadcast. Used them like that for years, only recently had a factory-back-conversion done in Berlin.

Actually, I'm pretty sure the VF14 was specified by Neumann for mic use - and there was a very limited amount ever produced. Only something like two or three production runs total, IIRC.
The rumor that it was a common tube comes from the fact that some category of factory rejects were at the time used in an external UHF-band extender for television tuners. I've never seen it used anywhere else.

/Jakob E.

edit/source: TFK Steel Tubes - Tab-Funkenwerk

Again, with all due respect i believe this is one of those nostalgia driven articles. Numerous other articles and facts seem to point to different vf14 origin story. Here's the link to alternate, yet document backed up version of the story, which makes more sense, at least to me.

Read the first post from Bernhard Nagel.
https://www.radiomuseum.org/tubes/tube_vf14.html

For non German speakers a short summary:

These two new steel tubes were presented in the Funk-Technik [FT] issue 21, 1947. A little later in December, the Funkschau [FS] followed with their description. With the VEL11 announced in December 1946, the VCH11 and VF14 were among the first new designs with a tubular steel base after the end of the Second World War. This post is about the pentode VF14.


By and large, the use of the new VF14 will be limited to special cases. Shortwave enthusiasts in particular will be pleased that there is now a low-noise, steep universal pentode with a separate braking grid for all-current operation.

The EF14 has grown far beyond its original purpose - FM broadband amplification for television receivers and low-distortion amplification in antenna amplifiers - in recent years and has become a real universal pentode. The same universal application also applies to the VF14. [...]

Tube production is one of the biggest bottlenecks for well-known reasons. The tube factories cannot even meet the urgent needs of the equipment factories. For the time being, it cannot be expected that the new tubes VEL11, VCH11 and VF14 will be commercially available and available to radio practitioners to build their own devices. Inquiries about these tubes at the tube factories are therefore pointless. [...]

This was completely normal from the autumn of 1947 until the currency reform in the summer of 1948, but by 1949 at the latest, the V tubes were also available in normal shops. The VF14 was listed in the 1951/52 broadcasting wholesale catalog (VERG) at DM 15.30 (VCH11 DM 15, VEL11 DM 15.20). In the tube pocket table (RTT) 8th edition 1960, the price of the VF14 remained unchanged at 15.30 DM. For comparison: A UF14/EF14 was 12.80 DM in 1951.

However, the VF14 was not to be used for the first time until 1949/50: as a preamplifier (impedance converter) in a triode circuit, G2 and G3 connected to A, in the newly developed condenser microphone U47 from the manufacturer Georg Neumann, Berlin. The conditions of use deviate completely from the "normal" operating values from the data table, the VF14 is "underheated" here with about 35 V at almost 40 mA (only 1.4 W heating power!) to achieve favorable noise properties.

Why the VF14 and not the otherwise identical EF14? The reason for this was the developer's requirement to operate the entire microphone circuitry from a (well-filtered) DC voltage of around 105 V only. In addition, there is a heating circuit series resistor of 1780 Ω attached to the base of the microphone, which converts almost 3 W into heat. So the entire U47 draws about 4.2W. The higher output voltage is required to provide the polarization voltage for the microphone capsule.


The steel tube VF14 was therefore available and [!!!] the new microphone U47 was developed by Neumann to suit it. Because there was no better fitting triode.[!!!]


Later tube condenser microphones such as the KM53a (1954) were then implemented with the specially developed AC701 microphone triode


[!!!] The original purpose of the VF14 was as a broadband RF amplifier [!!!]


Above all, I would like to thank the archive of the GFGF, Otmar Jung and Prof. Dietmar Rudolph for their support with research and data collection!

Also there are RFT produced vf14 tubes.

 

[gyraf]

You may very well be right, I agree specially about the nostalgia drivery - but I have never seen a circuit - or even an application note - for VF14 used in anything but microphone and the mentioned uhf/vhf converter circuit plus perhaps a magazine's suggestion for a 2-tube receiver?

Yes, I looked - for many years I hoped to be able to pinpoint some ancient radio/tv that sported these, then find it on the used- or antique market. To be made as a general-purpose consumer tube, it'd need to be sold for production-quantity - still we never saw this happening.

Last - I've never seen these mentioned anywhere outside of broadcast/studio/audio: Most multiple-use tubes saw broader frequency in the wild

As a side note, the EF14 behaves very, very differently than the VF - to a degree that I think they can be only remotely related even though the data sheet shows near-identical traits: https://www.filmsoundsweden.se/backspegel/ror-pdf/vf14.pdf

 

[kingkorg]

You're right, I don't have don't have any insight about their tolerances or how Neumann made their measurements. Any references were we can read more about it?

I don't understand what you mean with "just figured it out"? M7 was released 1932, I guess WW2 had a quite substantial impact on the continuity of their work but it had been around for many years when they produced it for U47.

This discussion is becoming a bit polarized. I know about the imperfections of tubes and capsules. I will try to find some time to record a couple of U47 and U48 with the same capsule so people can hear and decide for themselves. I'd love do the same with a couple of different new Neumann Berlin M7 but that's unfortunately not possible.

Does anyone know how predictable the sound of the respected U47-clones with M7 are (Wagner, Wunder, Flea, Telefunken USA etc)? I've heard a couple of Flea, two side by side. To my ears they sound the same.

I will do my best to find and post what you requested, however it takes quite a bit of time and energy as i do my best to do this stuff methodically.

I am aware some of my claims are often contrary to common view on stuff, but the reason is not to start a fight, but reveal to the best of my abilities what i found out during my mic world exploration.

I am empirically driven person, even though i am an artist, and creative soul. I have quite good developed hearing, but my experience tels me ears and brain can fool me quite easily. So i don't use it all that much when it comes to gear and replicating desired effects. I use hearing just as a final check. I have whole different approach when actually making music.

My road started by trying to find and quantify what are the aspects of special, rare, and expensive mics in order to understand and hopefully replicate desired effects. But i insist on measurements, and backed up claims.

During this journey i found out there are quite a few misconceptions out there, and i do my best to debunk them, simply to save other peoples time, money and help them use it instead on creating actual art.

Some of these misconceptions came to be simply because of people who try to make some money along the way, and maliciously spread lies on the topic, some more benignly just by repeating other's biased claims, justifying their purchases, bla, bla, bla...

I am not claiming by any means u47 isn't a special mic. I am not claiming the high tolerance makes it for inferior product to modern ones. I am just trying to point out to stuff within the design and how they really affect the whole thing, what might be the reason people hear what they hear.

There are woodoo, magic like effects going on in microphones!!!! I claim that!!!

My experience and measurements as source of these claims tell me most of these effects are due to acoustic/mechanic properties of microphones and how they render 3 dimensional sound happening around them into electrical signal. A lose wire, screw, cavity within the mic body will affect microphone sound way more than any decent tube, capacitor, or unobtainable component. No disrespect to anyone, but electronic part is piece of cake compared to the underestimated acoustic component.

 

[kingkorg]

As a side note, the EF14 behaves very, very differently than the VF - to a degree that I think they can be only remotely related even though the data sheet shows near-identical traits:

I always referred to this article you are certainly aware of, and used quite successfully EF14 in my builds. Don't misunderstand me, i am genuinely interested in what those behaviors are. As stated before, i'm all about acquiring new knowledge. Built for u47 or not, VF14 is a part of the equation.

http://www.moxtone.com/mU47_U47_part3.html

 

[Purplenoise]

If only you guys could be combined to make one person we would have the perfect mic haha..
Electronics knowledge, acoustics, aesthetic and some times..voodoo magic are equally important components to making an inspiring piece of gear that could actually be seen as an instrument rather than a tool

 

[kingkorg]

I don't understand what you mean with "just figured it out"? M7 was released 1932, I guess WW2 had a quite substantial impact on the continuity of their work but it had been around for many years when they produced it for U47.

Little bit on the variation during the early years. It is substantial.

https://web.archive.org/web/2010022...grosser.com/2009/10/m7-capsule-article-by-ag/
In case it gets lost:

M7 capsule-article by Andreas Grosser​

M7 capsule

The M7 capsule first showed up in 1933 and was skinned with a 10µm PVC. The material back then had to be – and still is today at MTG as well as STM – casted on water. ( The thickness of the material fluctuates between 10 and 12µm. After the war Neumann Berlin obtained their M7 capsules from Gefell, later on only the membranes . In 1955 Neumann Berlin hired a chemist responsible for the production of membrane films . In 1956 the first M7 capsules with PET polyestermembrane showed up. Those new capsules had a much better longterm stability as well as (because of the thinner membrane of about now only 6µm) the remarkable side effect of better low frequency response. In more than 50 % of all M49 microphones that were fitted with a M7, you can still find the M7 PET capsule, not only (like often times falsely assumed) the M7 PVC capsule. Since 1958/59 the M7 was abandoned and replaced by the K47 capsule. The failure rate in the production process of the M7 capsule was simply too high since you only had about 10 minutes to correctly position and finetune the membrane until the glue started to stiffen . The cogset of the K47 made it easier to finetune the membrane (it now got screwed on instread of glued Because of that the failure rate of the capsules got reduced drastically and so about 80 or even 90 % of the capsules could now be used after production. Back then the PET 6µm membrane film was obtained by the companies that also produced the capacitors.

 

[Purplenoise]

Does anyone know how predictable the sound of the respected U47-clones with M7 are (Wagner, Wunder, Flea, Telefunken USA etc)? I've heard a couple of Flea, two side by side. To my ears they sound the same.

I have only heard a pair of telefunken usa 251s side by side and one was definitely brighter than the other. I guess today tolerances are much tighter but still not 100%

 

[kingkorg]

This is what i refered to as stone age techniques:

"Very early diaphragms were actually made from a resin dissolved in alcohol cast on water. Eventually, PVC was dissolved in amyl acetate and cast onto gold dusted plates. "

 

[GeorgeToledo]

I have read that early resin was a form of collodian.

The shellac based glue Neumann used for M7 and PVC material wouldn’t hold the polyester material as well, which necessitated the k47 developed by IRT.

Neumann actually did rediaphragm old capsules for many years, including putting Mylar on old M7. I guess having one would be a true rarity, and would be especially great by the time they used more modern glue. They stopped doing reskins because of time and expense.

I think they’ve used Hostaphan a very long time. (edit: Hostaphan began BoPet production with 1954 pilot line in Wiesbaden, by 1957 full production, and k47/49 started production in 1958.)

 

[kingkorg]

I have only heard a pair of telefunken usa 251s side by side and one was definitely brighter than the other. I guess today tolerances are much tighter but still not 100%

That is exactly what i try to point out. Pretending those 251s are technicaly immaculate would be fooling your self, and everybody else. However that "mismatch" is part of the magic.

Now imagine some poor guy (me 10 years ago) trying to make a kit, replica, mod by using, in some aspects better and certainly way more consistent Røde type edge terminated capsule, in wrong body, spending money on exotic capacitors, transformers, tuning the circuit into oblivion.... No f$#*ng way am i going to get anywhere close.

However paying attention to internal body resonances (all the mechanical stuff found inside 251) does wonders!

 

[Purplenoise]

That is exactly what i try to point out. Pretending those 251s are technicaly immaculate would be fooling your self, and everybody else. However that "mismatch" is part of the magic.

Now imagine some poor guy (me 10 years ago) trying to make a kit, replica, mod by using, in some aspects better and certainly way more consistent Røde type edge terminated capsule, in wrong body, spending money on exotic capacitors, transformers, tuning the circuit into oblivion.... No f$#*ng way am i going to get anywhere close.

However paying attention to internal body resonances (all the mechanical stuff found inside 251) does wonders!

Yes. As I always say…it’s always a synergy of parts. It’s the combination that creates the magic and very rarely a part by itself.

 

[lightningbefore]

That is exactly what i try to point out. Pretending those 251s are technicaly immaculate would be fooling your self, and everybody else. However that "mismatch" is part of the magic.

Now imagine some poor guy (me 10 years ago) trying to make a kit, replica, mod by using, in some aspects better and certainly way more consistent Røde type edge terminated capsule, in wrong body, spending money on exotic capacitors, transformers, tuning the circuit into oblivion.... No f$#*ng way am i going to get anywhere close.

However paying attention to internal body resonances (all the mechanical stuff found inside 251) does wonders!

How does one pay attention to internal body resonances? Is it just buy a better mic body or are you actually doing something in there after getting the component in? Sorry if this is a dumb question but I am genuinely curious.

 

[Purplenoise]

How does one pay attention to internal body resonances? Is it just buy a better mic body or are you actually doing something in there after getting the component in? Sorry if this is a dumb question but I am genuinely curious.

Both haha…sometimes you might be able to dampen the body or add something to either dampen or brake/diffuse internal headbasket reflections or resonance. Other times you just have to get a better body. And some other times those “issues” might add character

 

[kingkorg]

How does one pay attention to internal body resonances? Is it just buy a better mic body or are you actually doing something in there after getting the component in? Sorry if this is a dumb question but I am genuinely curious.

Not a stupid question at all. I do it by performing various measurements. Not quite a walk in the park. If you are going after a clone, it's not the point to get rid of it, but match it instead. This exact point is driving me nuts currently, as im trying to nail a c800 clone, but i'm nowhere near done.

There is a body resonance, there is resonance of the cavity of the body (helmholz resonance), there's resonances and reflections around the capsule, angle of the capsule compared to the perpendicular bar of the grille, upper and lower in case of u47/c800 and such.

Elam is for example easy, the point is to kill all the resonances. I even have a mic which doesn't need any grille/shielding. As complicated as it sounds it's way easier to do.

U87s goal is also to have least resonances and reflections around the capsule. Sleve of the body doesn't resonate at all.

These effects show up in frequency response graphs, and are not subtle, several db of peaks and notches all over the place.

In case of u47 which has fairly microphonic tube (contrary to what many believe), you can replace the capsule with a 50pf capacitor, and listen to just the mechanical ringing of the components (microphonics). You would be surprised how much of a drum kit sound (high spl) the mic would pick up

 

[kingkorg]

Here's an example. This is same axact capsule in same exact circuit, but the upper body is very well damped, transparent grille, and the lower one is close to u47 type. Separated so you can see easier. No smoothing. So imagine having to match the lower response.

 

[kingkorg]

This is the same capsule, same electronics, no grille, so it's a naked capsule only attached to two different bodies. The difference comes only from body/sleve resonances, and slight difference in the size of the plate below the capsule. About 3db @5-6k. Very audible, very sensitive area. 2db @50hz

 

[ZHOUJUN]

I've tested K47 fixed ring will produce reflection, M7 almost flat, distortion smaller, so they timbre is different.