Micro U47

EUREKA !!!!
Plus de buzzzzzzzzz !!!!!!!

Why do they sound different? The Vf14 is in a neumann microfone underheated, there is a good reason why, so if you use a EF14 and run a seperate fillament at 4.95V the EF14 reacts identicle to the VF14. Only thing is you have to replace the VF14 fillament with a dummy to keep the kothode bias stiff. Stiff means that the filament current holds the cathode at the same level without the normal flux due to tube current, at high input level this keeps the cathode very stable without compressing. This circuit was first used in Telefunken gear in 1918!! So if you underheat the cathode and keep the dummy the EF14 sounds the same.

o3misha

post 63
I have U47 with VF14 . Believe me: low end is not the main thing. Dynamic in middle freqs is more interesting. And EF12 is much more useful than EF14 in many cases. With self bias you have totally different microphone. You have better transients (more stable bias) but you have absolutely different sustain on long notes and colored Hi-Fi -ish sound. I thing that weakness of self bias is not stable anode current and inflience of the cathode cap.


post68
I rejected Ef14 after 2 years of experiments with all possible biasing ways,-this is not the best tube. Self bias may give you good result , especialy with good cathode cap ( I used 200uF red Black Gate) but it is not U47-sh sound at all. With Ef12 I 've got the best result in first day. But I've got good advices from Andreas Grosser and very good transformer (much better than popular AMI). With EF12 sound is U47-ish, but you have to find right operating point.

post92
Guys , talk to Andreas Grosser about tube substitute of Vf14. He made Vf14er based on miniature Russian triod. If you prefer more heavy-muddy sound and if you don't like more leaner sounding Ef12, then you will be happy with vf14er. Its sound very close to Vf14. As for Klaus Heine - I will never listen to guy , who does not respect faсts and prefer woodoo dances around his idol VF14. I was removed from all forums where Klaus Heine is a resident because I was not agree with him and just asked him to prove his point. All he could say, my ears tell me this and that. blah-blah-blah. He prefer to talk about tubes differences than to work with microphones in studio. That explaines everything he says. And his business, of course. I do not trust the so-called experts who are engaged in repair microphones without understanding what is the correct calculation of tube amplifier circuit . For which to delete the messages, dispels myths and shedding light on the truth, it is easier than to prove the opposite. This disease is called purism, and it is very contagious.
I'll tell you more about all despised nuvistor that everyone (especially on forum of Klaus Heine ) considered bad for U47 - it's great tube for U47. Neumann's engineers made ​​a mistake in mode with nuvistor. The value of the cathode resistor is not optimal , because of what has changed with the correct matching transformer. Andreas proved it when he was approached for help with nuvistor U47 owners. Simple selection of the cathode resistor causes that nuvistor U47 sounds great. Andreas can help you in this . Just get in touch with him. Hi has unique knowledge and ears. He is a musician in the past. Do not forget this .
BTW: what biasing method you used for Ef12? It is very important to use right value of the anode resistor to get perfect low end. Andreas use this tube for replacement in old U47s (with usual BV08 transformer 6:1 or 6.5:1) many times for different clients. Many of his clients were very scrupulous in matters of sound. And none remained dissatisfied. If you think that the sound with EF 12 is too thin, it is likely that you made mistakes in setting up the microphone. It is necessary to choose the right all the components and modes in microphone. There is a small difference in the bass with VF14, it's true. But it should not be so much that you could talk about the subtle sound. EF12 is much softer and more comfortable than the EF14 sounds, it is not only a comfortable bass - mic with EF12 may work with higher SPL. Serious underheating leads to failure of 90% of the lamps, if at least every 3-5 years not to regeneration. At EF 14 filament, single, and not double like a VF14. Therefore, the cathode warms less evenly. The cathode material prone to failure with underheating more than VF14. In addition, the EF14 -very microphonic tubes. Very hard to find a decent lamp. If you are lucky - work with EF14 , it is not bad tube. But I repeat: it has a completely different set of harmonics, unlike the VF14. This EF14 sounds very unpleasant and harsh with big SPL. 8)

Ouh yeah ! Tu nous enregistre un petit sample pour voir comment ça sonne ?

c'est fou je viens à peine de lire ce truc lol
j'ai meme cherché sur google traduction ce qu'etait dummy

d'ailleurs j'ai pas tout saisis.
j'ai aussi lu ça et beaucoup de monde adorent la ef12 par rapport à la ef14

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en gros pour résumer la ef14 est plus aggressive mais a un son plus epais car elle a plus de bas mid
la ef12 est plus smooth avec un aigu et un médium plus proche de la vf14 que la ef14, les gens la qualifie aussi de plus hifi

La seul chose sur lequel j’hésite c'est si j'utilise toutes les valeurs originales ou si je remplace R1 et R2 par des 1Gohms...

the EF12 tube is much better than the VF14; UF 14 or EF14 tube
lower noise and much lower microphonic

en gros de ce que j'ai retenu c'est que beaucoup de gens disent que justement pour se rapprocher du u47 original la ef14 est le meilleur choix, car il ya 14 dans le nom et donc ça influence, et que les caractéristiques sont quasiment les mêmes

mais apparement le fait de sous alimenter le heater dans la ef14 cree des problemes car le filament n'est pas chauffé uniformement

The EF14 has a different impedance, and it also sucks quite a bit of current for the heater and that results in a higher temperature inside the mic..

Aditionally the high current needed to drive the tube heater makes the wire from the PSU to the mic behave more like a resistor, in the sense that there is a higher voltage drop across the wire.


The EF12 is a cooler-running tube and it behaves differently.

Sound-wise, the EF 14 has more punch in the bass and mids but less detail in the highs than an EF12.

I have built preamps and phono amps as well as mics with both and I can say for general-purpose detail and smoothness the EF12 is probably better...but it lacks the authority and punch of the EF14... say on drums or lead vocals.

As far as both being used as an alternative to VF14, the EF14 is closer to a VF14, but the EF12 is probably better suited in the application, when running at full voltage on the heater.

The EF14 has the heater filament which is wired differently and it will not heat uniformly in a starved-filament circuit.

malheureusement je ne peux pas partager le schéma car j'ai promis à andreas de le garder pour moi
ce qui est compréhensible, c'est deja vraiment gentil et c'est le seul à avoir partagé ça avec un inconnu.
essaye de le contacter, mais sinon je l'aurai partagé volontier.

ils parlent de relier suppressor to grid dans le cas d'une ef14
de quoi veulent t'il parler?
apparemment ça a un effet positif allié a un self biais et une valeur de résistance de 2,7K sur la cathode découplé par un condo 100uf

The EF14 has a different impedance

-granger.frederic

Dear o3misha,
you said that ef12 is the closest.
Do you have compared it with a real vf14M in a genuine U47 ?
Do you have some shootouts ?
regards
Fred


-o3misha
Not in one mic, but with the same capsule. Yes I tried Ef12 tube in comparisson with EF14 and VF14. My 2 orig u47s with VF14s are different in sound, inspite of the same type of tubes ( all VF14s are different ). I made third microphone with Haufe BV08 x-former (which is the best copy of BV08 transformer today IMHO) and I tried EF 14 ( about 10 different tubes) and only 2 EF12K. IMHO EF12k is closer to VF14. It is still not the same with VF14 in lows, but it has very close behaviour in high and middle freq-s. But you have to correct anode resistor and anode feeding for EF12. It also operates better with higher anode current -1mA than VF14 (0.5mA). EF14 has much more highs and the sound is not soft even with very low filament voltage 4.5VDC-5VDC. The bass respones of EF14 is closer to VF14, but it has less dynamic in middle freqs. But some people like it. I prefer more soft sound with good dynamic in middle freqs. Flea, Andreas Grosser, Wagner prefer Ef12 as the best tube for U47 today. And I agree. I would upload files with EF12 tube, but unfortunately I already moded this mic with original VF14 tube.

Voilà comment je réfléchis : Je remplace la VF14 du schéma directement par une EF14 ensuite je détermine point par point ce qui ne va pas avec une EF14

1 - L’alimentation, il me faut donc 0.47A pour le filament et disons 5mA pour l'anode (ce qui me laisse de la marge), plus une petite marge de sécurité, donc arrondissons le total à 0.55A 150VAC ce qui me donne 57.75VA, allez hop j’arrondis à 60VA, j'ai donc déterminé les caractéristiques de mon transfo d'alim. Ensuite je calcul mon alim pour avoir 105V en entrée de mic. a partir de là la seul chose qui change dans le schéma c'est R4 qu'il faut recalculer !

Dans ce cas pourquoi ne pas faire chuter une partie de la HT dans l'alim via une ou plusieurs resistances (jusqu’à 12V pas exemple), puis dissiper le reste dans le micro afin d'obtenir les 5V et la température originale !?

apparement certains disent qu'il est possible de reparer une vf14 en mauvais etat donc peu être que d'en acheter une rincé et la remettre neuve peu être interessant, il ya un guide qu'on peux acheter sur ebay apparement quelqu'un avais mis le lien sur ce topic.