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[soapfoot]

It's well-known that the opinion of the best ears and experts is that there is no substitute for the VF-14M in a U47-style microphone circuit.

However, the fact that those tubes are in extremely limited supply has prompted many builders to use various alternate tubes (certainly with various results).

Since there's such a knowledge pool here, it would be great to see some experts weigh in, subjectively (based on first-hand experience, of course) about the sound and relative timbral qualities of these tubes in that circuit (assuming the necessary external heater voltages and other necessary changes have been made for each tube).

Here's a list of tubes that have been used as substitutes, off the top of my head.  I'm sure it's by no means comprehensive, so feel free to add your own.  Please do comment on any or all to let us know how you feel about their sound/function in this circuit--either compared to the correct VF-14M, or just in general.  If some work poorly with minimal modification but work very well with more extensive re-working of the circuit, that would be good to know.  I'm interested in synergy with the BV8 transformer, M7 or K47 capsule, and headbasket design (in particular).

Here's my (incomplete) list, in no particular order (ignoring the 13CW4 nuvistor, since we've all heard the opinions of that one):

UF14
EF14
EF12(k)
EF12 spez
EF13
EF42
UF42
EF80/800
EF802
EF804/6F40
EF86/806
EF91
EF94
PF86
407A
5840

Thanks in advance.

[klaus]

If we can limit the discussion to the genuine Neumann U47 product whose only variable is the tube (and all necessary circuit/component alterations) then I can tell you from my 30-year personal experience:

1. None of the alternatives you mention will recreate the magic of a VF14 mated to the existing U47 circuit/capsule. And the reason is quite obvious: all the tube you cite are cheaper and more readily available than a VF14. That is the ONLY reason anyone has ever looked at any of these alternatives, not because they would yield superior audio, regardless how you define superior.

2. UF and EF 14, while somewhat related to the VF14 in construction and outline, have an overheating handicap which is only overcome by feeding a second voltage into the mic- a major mod. While these tubes can theoretically be biased in a similar way as the VF14 (fixed) the less noisy option-cathode biasing- will yield a substantial deviation in sound- thinned out, glassy, quite transparent, yet leaning towards body-less.

3. As soon as you exit the steel-tube world and look towards some of the high quality Telefunken designs like EF86/806/804 etc. you get into trouble with the existing transformer configuration: a bad match.

I gave up after these and similar kinds of experiments, and realized that the U47 and VF14-combination is a match made in heaven, and should be left alone. There ARE enough VF14 out there, but an increasing number of U47 seekers feel a five figure price is too steep for their pocket book (understandable), and are lured to substantially cheaper supposed alternatives by posters who claim authority- sometimes individuals with a vested interest (not understandable, in my book).

I do not wish to devalue the role U47 copies, re-interpretations, etc. can play for buyers who simply are not in a position to shell out five figures for a fifty year old microphone- some of these U47-inspired mics are quite nice in their own right- but I caution anybody who is after "that" sound not to fall into the trap discussed by hobbyists and eternal U47 wannabes: there is no substitute for the VF14. Period.

[duskb]

There ARE enough VF14 out there, but an increasing number of U47 seekers feel a five figure price is too steep for their pocket book (understandable), and are lured to substantially cheaper supposed alternatives by posters who claim authority- sometimes individuals with a vested interest (not understandable, in my book).

It's almost pointless to even consider "available" VF14s as a viable replacement at this point because they're either stupid money or were most likely rejected by Neumann at one point anyways.

The whole discussion is moot IMHO. The VF14 is an endangered species and every U47 requires one to make it work. Until someone decides to put the VF14M back on the market owners can either watch their (expensive) microphone sit on the wall or put it back into service with whatever substitute they can muster up.

In the not too distant future even ($x) won't put a VF14 into a U47 so we may as well have the discussion now rather than later. These things won't last forever and the mic's they go in actually might.

Dusk Bennett

[Bubba--Kron]

I have the BeesNeez T1 here which is a fantastic mic with the NOS EF12.   Its very warm and sweet, and seems to have a bit slower attack and slower transient response than a U47.    Its nothing that good compression cant fix, but it does not have that Roger Waters authority to it that only a real U47 seems to have.

Its still a great tool and I am very happy with it, but it makes me realize why the real ones are so expensive.  I still plan to rent a U47 for certain tracks on my own album.  That being said, the T1 is a incredible mic and has its own style and uses that can be taken advantage of!!!!!!

Cheers

[Kai]

2. UF and EF 14, while somewhat related to the VF14 in construction and outline, have an overheating handicap which is only overcome by feeding a second voltage into the mic- a major mod. While these tubes can theoretically be biased in a similar way as the VF14 (fixed) the less noisy option-cathode biasing- will yield a substantial deviation in sound- thinned out, glassy, quite transparent, yet leaning towards body-less.

I've build a mic using the M7 and EF14.
I used fixed bias and underheating proportional (powerwise) to the VF14.
The circuit is exactly the same like in the U47, except for the resistor values in the heating branch, and of course I used a separate heating supply voltage.

Another difference is a fixed cardiod/variable pattern switch similar to the one in the U48, but with variable (external) biasing voltage for the capsule backside.
Switched to cardiod (on the head basket) this is out of circuit.

There is no noise problem with this mic, and none of the above mentioned soundproblems.
I don't have an U47 for comparison, so I can't tell how far they are apart.

I have lot's of other highclass mic's, and this one is at least on par with them.
Sound character is warm and transparent.
It can take quite an amount of treble boost when necessary without becomming grainy or sibilant.
It's very easy to handle in the mix.

Regards
Kai Schluenz

[klaus]

Good to hear. Would be nice for you to be able to do a side-by-side comparison with a genuine VF14-U47.

I found the VF14- proportional underheating of the EF14 not only problematic in terms of timbre and dynamics, but also in terms of premature caking up of the cathode.

[Mojave]

Im not an authority by any means but I am an owner of a Telefunken USA U47 with their VF-14k and it sound excellent. I also see the tube by Wagner called the VF-14W.
Klaus, Can you comment regarding these two varieties of VF-14 vs. VF-14k or VF-14W?

[klaus]

Yes,
I can comment that, despite repeated promises by representatives of Telefunken/USA, I have not received a tester of their glass tube-in-a-metal jacket they call "VF14k". I can therefore not make any statements what such a tube would sound like.

[Mojave]

There ARE enough VF14 out there,…..

Would you mind sharing where to look? I can only find one or two. I assumed mainly to look overseas.

Thanks

[klaus]

Victor,
Jus as in your world of vintage Marshall amps, there is a collector's network out there which rarely becomes visible to the uninitiated, but, suffice it to say, the vast majority of remaining VF14s resides with these people (as probably do the vast majority of remaining Plexis!)

EBay.com or eBay.de is a more accessible source. So is Gearslutz classifieds (post a "wanted" ad) also scan all of craigslist via a Google search.

[Mojave]

Of course,
Thanks much

[klaus]

One more thought:
The recent surge in the quest for tubes to sound like a VF14 seems to coincide with the recent surge of copy mics available on the market. Manufacturers of these mics, in order to be profitable, cannot  sell them at the price point of a genuine U47.  Therefore they need to calculate carefully what parts go into these mics, in order to make them financially attractive. With other words, a mic which wholesales for $2k cannot be equipped with a tube that costs $2k, or a capsule (were it available from Neumann at quantity) that costs close to $1k.

As it is generally agreed that three core components in a U47 (capsule, tube, transformer) determine its sonic signature- probably more than all the other components in that mic combined- it seems reasonable that manufacturers of copy mics try to circumvent the cost of these components by suggesting that their alternatives are perfectly acceptable.

Then often comes the time when the owner of such mic seeks to improve its sound (why, must I ask, if the copy mic is that good, would one do that, unless a deficiency is perceived?), but does not wish to do what the manufacturer also did not do: spend the money for the vintage component upgrade. 

That brings us to the Catch 22 where we are today: mic lovers want the sound of the vintage original. They figure that, if they could swap out one or two magic ingredients of their copy mic, it would get them there. But they are often hesitating to spend the money for these parts, then seek the internet for alternatives, of which plenty are advertised, with plenty of promises to that effect, only to end up where they started (minus the money they had spent): still desiring the sound of the vintage original.

[soapfoot]

Klaus,

While I agree with what you're saying, I do feel that there is another category of person who might be interested in answers to this commonly-posed question--

The microphone enthusiast who is interested in building microphones--and is trying to learn about the various tubes available that could be experimented with for their build project in order to subjectively evaluate the sound and character of each (learning in the process) or even so that they may weigh out the pros and cons and do a cost/benefit analysis of the choices--may be most interested of all. 

The elegant simplicity of the U47 head amp probably makes it an appealing platform or jumping-off point for people just exploring tube condenser microphones. For those less interested in attempting an exact copy than they are in taking inspiration from the essential simplicity of this most iconic design, the information about possible tube alternatives would be most welcome indeed.

Best regards,

--brad

[klaus]

Good point, and certainly a (small) section of the buying public I overlooked in my diatribe.

[Piedpiper]

That brings us to the Catch 22 where we are today: mic lovers want the sound of the vintage original. They figure that, if they could swap out one or two magic ingredients of their copy mic, it would get them there. But they are often hesitating to spend the money for these parts, then seek the internet for alternatives, of which plenty are advertised, with plenty of promises to that effect, only to end up where they started (minus the money they had spent): still desiring the sound of the vintage original.

There are also many of us that are less attached to the exact idiosyncracies of the original than we are in something similar that is very good, and maybe even from some standpoint "better". I, for instance, have preferred in some ways Andreas Grosser's glass tube alternative to all other options.

Also, I personally, have no resistance to paying for what I want to hear.

Cataloguing the differences of the different options would be useful from a number of standpoints.