EF 14 Tube for Mic

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Is this tube still in production?
Is there any NOS around?
If there is NOS, I'd expect them to be the runt of the litter due to their
age.

To quote Eddie Cilletti from 1997, "Joe Leung at Gotham Service Labs
(212-967-3120) tells me there are similar pin-compatible tubes ‹ the EF-14
and the UF-14 ‹ which are somewhat more available and less pricey (about
$350). This approach requires no mechanical modifications although a few
circuit changes are necessary. At one time, Neumann made a Nuvister "kit"
which adapted a subminiature tube to fit in the original socket. Nat Priest
(212-343-0265) created his own version of this vacuum tube alternative for
under $200. Stephen Paul Audio also has a more modern, nine-pin upgrade.

More at: http://www.tangible-technology.com [...] /u-47.html

Smiles,

Ty Ford



-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com

Archived from groups: rec.audio.pro (More info?)

Ty,

Production of VF/UF/EF 14 (steel) tubes was discontinued by Telefunken
in about 1957. An East German factory continued making them for another
eight or ten years after that.

The other tubes have distinctly different filament voltages from the VF
14. So they may have similar pinouts but they certainly aren't direct
replacements. The UF 14, for example, requires about half the filament
voltage and twice the current.

But the U 47/48 didn't have a separate power supply line for the
filament voltage--they obtained that voltage from the plate voltage via
a dropping resistor. Plus the VF 14 was run at lower than its rated
filament voltage to begin with. So if you are going to change this all
around, doubling the current while halving the voltage and dropping it
another 25% or so to parallel what was done with the VF 14, it starts
to become highly questionable whether you want to dissipate so much
heat in a dropping resistor inside the microphone.

Thus if you opt for a really thorough engineering solution using a UF
14 or EF 14, it will probably mean replacing the connector, cable and
power supply of the microphone. And there is considerable debate over
whether the sound of the microphone with either of those tubes used as
substitutes is the same as with the VF 14. The Nuvistor replacement is
said to be even farther from the mark.

This truly isn't my area of expertise so I'll just limit myself to
those remarks, plus mentioning that Joe Leung's company (Gotham Service
Lab) unfortunately went out of business this past year; he sold his
parts stock to Tracy Korby and disbanded the company. So I wouldn't
post his old phone number on the Internet any more--at some point
fairly soon it (the phone number, I mean, not the Internet) will
undoubtedly be assigned to someone else.

Much more information is in the archives of Klaus Heyne's section of
the PSW Recording Forums on http://www.prosoundweb.com/forums and
Neumann's Pinboard at www.neumann.com/pinboard .

Archived from groups: rec.audio.pro (More info?)

On Mon, 27 Dec 2004 12:53:50 -0500, David Satz wrote
(in article <1104170030.303897.313000@z14g2000cwz.googlegroups.com> ):

> Ty,
>
> Production of VF/UF/EF 14 (steel) tubes was discontinued by Telefunken
> in about 1957. An East German factory continued making them for another
> eight or ten years after that.
>
> The other tubes have distinctly different filament voltages from the VF
> 14. So they may have similar pinouts but they certainly aren't direct
> replacements. The UF 14, for example, requires about half the filament
> voltage and twice the current.
>
> But the U 47/48 didn't have a separate power supply line for the
> filament voltage--they obtained that voltage from the plate voltage via
> a dropping resistor. Plus the VF 14 was run at lower than its rated
> filament voltage to begin with. So if you are going to change this all
> around, doubling the current while halving the voltage and dropping it
> another 25% or so to parallel what was done with the VF 14, it starts
> to become highly questionable whether you want to dissipate so much
> heat in a dropping resistor inside the microphone.
>
> Thus if you opt for a really thorough engineering solution using a UF
> 14 or EF 14, it will probably mean replacing the connector, cable and
> power supply of the microphone. And there is considerable debate over
> whether the sound of the microphone with either of those tubes used as
> substitutes is the same as with the VF 14. The Nuvistor replacement is
> said to be even farther from the mark.
>
> This truly isn't my area of expertise so I'll just limit myself to
> those remarks, plus mentioning that Joe Leung's company (Gotham Service
> Lab) unfortunately went out of business this past year; he sold his
> parts stock to Tracy Korby and disbanded the company. So I wouldn't
> post his old phone number on the Internet any more--at some point
> fairly soon it (the phone number, I mean, not the Internet) will
> undoubtedly be assigned to someone else.
>
> Much more information is in the archives of Klaus Heyne's section of
> the PSW Recording Forums on http://www.prosoundweb.com/forums and
> Neumann's Pinboard at www.neumann.com/pinboard .
>

Thanks David,

I was pondering the Peluso mics and the note that on that was described as
seemingly close to a U 47 appeared to be using EF 14. I thought, "Hmm., how
old ARE those tubes? Are they any good? Are there any good ones left or are
the remaining NOS just the clunkers that nobody wanted in the first or second
place.

Smiles,

Ty Ford



-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com

Archived from groups: rec.audio.pro (More info?)

Chris Hornbeck <chrishornbeckremovethis@att.net> wrote:
>
>If someone would sent me a schematic of their mic, I'd love to
>see what's so special. "F" is a pentode; no magic possible?
>There are other low-noise pentodes, comparatively easily available,
>that may be kludged in with a separate filament supply. 5879s, 6267's,
>etc. Does it really require a pentode, anyhoo?

The thing about the U-47 is that it uses a particular kind of pentode
with the filament running at lower-than-rated voltage for longer life.
This means first of all that the original VF14 tubes hardly ever fail,
but it also results in a major nonlinearity issue since the tube is not
intended to run with such low emission.

I am assuming the VF14 was chosen because it was cheap and plentiful on
the surplus market at the time. They were used in the Volksradio,
thousands of which were discarded after the war when people were allowed
to listen to foreign broadcasts.

That nonlinearity issue is part of what some people like about the U-47.
Later on, when the nuvistor became available, Neumann engineers realized
this was a much better way of getting the same degree of reliability.
This, the improved nuvistorized U-47, which doesn't have the linearity
problem of the low-heater VF14, and which people today don't seem to like
as much at all. I think it's a much cleaner mike, personally.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."