Why is this tube different from all other tubes?

[strangeandbouncy]

Hi,


   I have a u48 that has had the VF14 replaced with EF14. The mic had very noisy tube when  i got it 15 years ago. I had it changed to EF14. It sounds truly amazing, and has been used on countless records. No-one has ever said anything bad about it, and many, including, for example, Stevie Wonder, have complimented it. Whenever I go anywhere with a VF14'ed u47, I try mine against it. I cannot comment for the condition of other peoples VF14's, and I guess that there are many that are being used well past there useful emission state, but mine ALWAYS wins. Always. Every time. Hands down.

  Maybe if I could FIND a decent VF14, and paid to have it put back into my mic, my particular combination of capsule(not original kk47, but a new one 15 years ago), transformer and components would sound even more amazing, but i doubt if I will ever get the chance to find out.

  I personally think that there is a greater range of tonal differences between individual capsules than there is between EF14 and VF14. Add to that, there are two different types of capsule found in u47/48, ie M7 ant KK47, and a couple of different transformers. I have heard a few modern remakes with UF14 in, and I can say for sure that they were all very very dark sounding. That could have been as a result of anything, not just the tube, so this is an unqualified speculative comment.


  there are certain places on the internet that to uphold this opinion would be to offer myself up as pariah. I can only comment as I find. I am a seasoned professional with some success, and I hope a good pair of ears on my head. I suspect that many who pooh pooh the EF14 solution(which i had take, or not have a functioning mic!) do not actually USE mics very often, and certainly have a vested interest in the unbelievable price-hiking of the scant tubes remaining. Interesting that the same people now have stockpiled all remaining EF14's. I Recently, I tried to find a decent EF14 as a spare, not that i need one right now. I was offered an "Un-tested" EF14 for $150!!!!! as opposed to a "tested" one for £250 . . . . (do I really have SChmuck tattoed on my forehead?) I shan't name names. Suffice it to say I was very disappointed.


   Of course if anyone has a VF14 for sale at a reasonable price, I would love to put mine back to original, for historical and financial reasons. And curiosity, since I would love to personally prove the hype one way or the other. In the mean time, I have a perfect, wonderful, adored mic that gets used nearly every damn day.


   Kindest regards,



       ANdyP

 

[mad.ax]

AFAIK, the VF14 has been used in Neumann mics, U47, U48, and MM2 (measurement microphone). Those mics were supposedly all fitted with the VF14 M version.

Now the only other product that I know off which use a VF14 (along with a VCH11) is a small and cheap radio, branded: Horst Hewel
http://www.radiomuseum.org/r/hewel_ukw_vorsatz.html

Funny to see the most expensive Telefunken tube of the time used in such a cheap consumer product. The theory would be that those cheap radio were only made to use the Neumann rejected VF14, as no other manufacturer wanted to buy such an expensive pentode.

I still have to see or hear off any kind of military equipment, antenna amplifier, or anything else with a VF14 in it.... With all the research and hunting which have been done for years about this tube, I doubt that it wouln't have showed up!
So for now, I'll stick with the special purpose theory...

Axel

 

[Jonte Knif]

So, who is going to trace the curves? My EF14 is used, so not the best candidate. I can get VF14 to try but because of its price I really would feel scared to touch a new one.
How ever I asked a friend if he has some tubes that have gone noisy but could otherwise be good. Ultimately I need more than one sample to be sure.
I can more easily make analysis of the tube in the mics and would be allowed to do so. (I've done it for the nuvistor versions and they suck badly), but curves would be cool.
I'm very interested to do the job, but if someone has new VF14 at hand (and perhaps even a curve tracer), please go ahead and trace the curves both with full heat and reduced voltage.

I do like the BV8 concept -- that it's full of highly complex harmonics which makes the circuit sound rich.  It's not "clean."  It's dirty and complex.  The U47 I've heard sounded just like that, big and fabulously rich and complex.

There are several U47 around here and they all sound different. The one that sounds "best" is clean. We all know they are different but it is hard to tell what the "original" sound was. I doubt that a dirty sound would be the starting point.

I doubt NEUMANN engineers then spent thousands of hours in comparative subjective listening tests,nor did they had thousands of different tube types to choose from.

Of course not. They were engineers I don't claim that every vintage product was designed without a lot of listening tests, but I think it applies to most "mystical" items. They just happen to be above average.

there are LOTS of possible (cheap) substitutes : all you need is a triode (or triode-connected pentode) with the same electrical characteristics/curves as the under-heated ("starved") VF14,low grid current/leakage and low noise/microphony.

This is quite bold claim. Could you point out for example 10 candidates for starters. What are the requirements? I would say Gm and mu around +-20% of VF14 and low microphonis and low grid leakage. The high Gm and low grid leakage _combined_ are not to be found in many tubes. Because of the immense amount of tube types made there must be some which are close enough, but I am not aware of them and most other people aren't either. So your info would have enormous benefit for many people.

We all know these professionals (especially one...) who trumpet all the time that there is no substitute and when asked what is sooo special they turn into "you obviously haven't heard one. I've done million comparisons. You know nothing about good sound." Period. No explanations beyond that and it makes me mad.

Unfortunately,vintage genuine VF14's in good condition are extinct and will never be reproduced. (Sorry, TFKUSA !)

Sorry but there are some, and my friend sells them sometimes to that company in question. _Unopened m-labeled boxes_ from local radio, I think. TFKUSA has been happy with them. But of course, quantities are not that great. I'm also aware of one guy who has more of them, but only sells one at a time. Great pension plan these days.

-Jonte

 

[mad.ax]

Back to the original topic: Why is this tube different from all other tubes?

If we compare it to it's closest cousin the EF14 we get:
-Different heater wire and construction (double helix) This is supposed to give better tolerance to under heating, and more uniform heating of the cathode.
-Different cathode material
-Better insulation of the grid, leading to higher input impedance

Oliver Archut also mentioned different grid material and construction, but he didn't gave more details.
I've also read about a different base material (for better insulation) only used on “M” stamped VF14, but since the “M” stamp was the result of testing and selecting, I don't see how they could have change the construction after!

The VF14 is not “magic” by itself; its presence in the Horst Hewel radio doesn't makes it sound “wonderful”.

What is “magic” is the combination of VF14 + schematic + BV8. And one can add: +M7 + grill design...
I guess Neumann's engineers started with the VF14 and from there designed the BV8 to match.
I guess that's what Max did with his MK7.

Axel