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)
