U47 with EF14 tube Build

[Spencerleehorton]

Hi All,

going to hopefully be attempting a U47 with a EF12 tube once they arrive but have noticed that the EF12 has a kathode connected to the top grid?
normally the top and middle grid are attached with the anode?

could someone chime in on whether this will be a problem please?

 

[Khron]

normally the top and middle grid are attached with the anode?

"Normally"?

https://www.yumpu.com/en/document/read/3766247/pentodes-connected-as-triodes

 

[Spencerleehorton]

find quite contradictory information:

here says the EF12 is not suitable for a U47

http://www.moxtone.com/mU47_U47_part3.html
AEG use them and say that both EF12 and EF11 are perfect?

http://microphoneboutique.com/product/aeg-moscow-mkl-49/


found a diagram

 

[Khron]

Component fetishizing...

 

[rock soderstrom]

could someone chime in on whether this will be a problem please?

No problem, see Khrons linked presentation. The 5654/E95F and other tubes also have this hard wiring from G3 to the cathode.

I am curious about your experiences and will follow your new adventure with excitement.

 

[Tubetec]

When you thinkabout it 1400 or so Euros for the AEG is a good deal for what your getting , a hardwired tube mic , compared to some top branded stuff thats not to far from off the shelf Chinese ,but costs many thousands .

 

[Spencerleehorton]

trying to explore all avenues within a fairly small budget, once this one is done i can then compare all i have then choose what i feel is best.

 

[Drosselmeier]

AEG can make U47 with any pentode

 

[Spencerleehorton]

A toroidal output transformer!!?

 

[Kim Culhan]

find quite contradictory information:

here says the EF12 is not suitable for a U47

http://www.moxtone.com/mU47_U47_part3.html
AEG use them and say that both EF12 and EF11 are perfect?

http://microphoneboutique.com/product/aeg-moscow-mkl-49/
View attachment 112873

found a diagram

That grid, internally connected to the cathode, is the suppressor grid.

suppressor grid​

n
(Electronics) an electrode placed between the screen grid and anode of a valve. Its negative potential, relative to both screen and anode, prevents secondary electrons from the anode reaching the screen

 

[tomas.borgstrom]

EF12 is a great tube for a U47 copy but use a lower value than 100K for the plate resistor. It will give better low end and a sound that is closer to U47. You can go as low as 10K. Look at the CMV 5/B schematics. If you use a negative heater voltage you can use a voltage divider to get about -2V to the grid. Once again look at the CMV 5/B schematics fo inspiration.

A high quality M7 is the most important.

 

[Spencerleehorton]

We’ll all the bits have arrived but I got a EF14 rather than a EF12 like I ordered.

 

[MagnetoSound]

find quite contradictory information:

here says the EF12 is not suitable for a U47

http://www.moxtone.com/mU47_U47_part3.html
AEG use them and say that both EF12 and EF11 are perfect?

http://microphoneboutique.com/product/aeg-moscow-mkl-49/

AEG also say: ‘The capsule is a faithful reproduction of the U67 capsule made in our own workshop’, so you have to wonder either how accurate their marketing blurb is or how they get away with calling it a ‘U47 inspired microphone’.

 

[Spencerleehorton]

I’ll build it with the EF14 and order a EF12 to compare, as all info points to EF12 being better overall.

 

[rock soderstrom]

I’ll build it with the EF14 and order a EF12 to compare, as all info points to EF12 being better overall.

 

[Tubetec]

I think its fair to say its U47 inspired ,
Its one of the few true hardwired tube mics in production ,


Where did you buy the U47 body Spencer ?

All these EF type tubes have differing properties ,
how does this play out when the tube is triode connected ,
whats the best way to configure the suppressor and screen grid ,

Its interesting they way they configure the heater/cathode in the AEG ,

To me anyway going the EFxx route to building a U47 replica seems like the smart choice ,

 

[Spencerleehorton]

I got all the bits from alibaba

U47 body
Bv08
M7 capsule
Tube socket
EF14 tube

I will test both P2P and EF14 in this body, then will either buy and make another body and I have another 3 or 4 bodies I can make with the bits I have but have to say these bodies are really nice.

Going to buy a ELAM 251 body and upgrade my 251.

 

[Spencerleehorton]

Also just to mention I have some 1uf oil and paper caps to try once I get back off my holiday!!!

 

[Spencerleehorton]

just a quick question in case ive thought about this wrong, for the 7 pin connector into the mic body is it just a male 7 pin XLR?

if so where are you guys sourcing?

 

[Khron]

Look up Cliff UK connectors You can scavenge the insert from their old-style panel-mount connectors.