Micro U47

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.