Insight into "U47-inspired" with EF12 tube?

soapfoot · Jan 5, 2011

Hello. This is my first post here-- sorry to dive right in with questions, but I do promise to stick around. Before my membership was approved, I lurked for a long time and I've read many wonderful threads here, using the search function, about DIY U47-alike microphones.

I found one blurry schematic for use with an EF12 tube, of which I have a very nice NOS Telefunken.

I'd like to make a mic using the TAB/Funkenwerk stuff, Thiersch Blue Line capsule, and this tube.

Does anyone have an experience or wisdom to share, a cleaner/readable copy of the EF12 schematic, validation that this schematic is correct and works, or anything else?

Thanks a lot. Great forum you have here.

Sredna · Jan 5, 2011

Check out Klaus Heynes forum, there were recently a thread about EF12 and DIY U47.

soapfoot · Jan 5, 2011

Thanks. I'm a member over there as well. When I get a few more of my parts/thoughts together, I might ask more in-depth questions there. Klaus runs a pretty tight ship, and is pretty passionate about having the discourse be 'meaningful.' I don't want to step on any toes.

Biasrocks · Jan 5, 2011

I found this thread which has some good info.

http://www.groupdiy.com/index.php?topic=22730.0

And

http://www.groupdiy.com/index.php?topic=41549.0

Here's a schematic for the EF14 tube.

Mark

zebra50 · Jan 5, 2011

Here's mine... again

http://www.groupdiy.com/index.php?topic=39541.0

soapfoot · Jan 5, 2011

Biasrocks said:
I found this thread which has some good info.

http://www.groupdiy.com/index.php?topic=22730.0

And

http://www.groupdiy.com/index.php?topic=41549.0

Here's a schematic for the EF14 tube.

Mark

Thanks! I plan on using an EF12 in mine, instead of the EF14 or VF14 (or UF14).

Question-- did you find you had to sort through a bunch of EF14 to get a "good" one? Klaus, Oliver, et al seem to say that you can plan on doing this.

soapfoot · Jan 5, 2011

zebra50 said:
Here's mine... again

http://www.groupdiy.com/index.php?topic=39541.0

beautiful!

MagnetoSound · Jan 5, 2011

You even did the badge?? (wags finger ...) ;D

zebra50 · Jan 5, 2011

MagnetoSound said:
You even did the badge?? (wags finger ...) ;D

Only for the photos and a giggle, badge was a purple one off a KM84, stuck on with sticky tape.

Actually when it was all finished I didn't want to put someone else's badge on - it'll get an my own badge when I get round to it.

MagnetoSound · Jan 5, 2011

Good man! We should all have our own logos and badges, IMO.

Which tube is that again? Did you have a chance to compare it in a 'shoodoud ziduation'?

e.oelberg · Jan 5, 2011

this could be an inspiration, this is what Telefunken USA is selling as VF14.

Very likely it's also JAN 6028
like in Max's kit, and the resistor looks like 3.6k

nicholas

zebra50 · Jan 5, 2011

408A also looks like an interesting possibility, 20V heaters IIRC. I have a load but have never really tested them properly in a mic. On the 'to do in 2011' list.

MagnetoSound said:
Good man! We should all have our own logos and badges, IMO.

+1. I have some nice enamel Xaudia badges for front panels, but they don't bend well

Which tube is that again? Did you have a chance to compare it in a 'shoodoud ziduation'?

Not with a real U47. Some of kind forum members offered to help out, but geography gets in the way. One day...
It's won a couple of vocal shootouts in our little studio, but has lost a couple also. (The Josephson keeps winning.)

soapfoot · Jan 5, 2011

This is what I'm working with right now, so far. It's the only part I have.

I got a pretty good buy on it, NOS, and I've been wanting to build a mic anyway. I've done a fair amount of reading, and everyone has a (passionate) opinion about tubes to use in "U47 Inspired" mics. I use the word "Inspired" because some people get extremely offended at the notion that a microphone without the VF-14 could even be called a "U47." So I'll not do that. I don't have enough personal experience to have a genuine opinion either way.

However, the EF12 is (or at least was at one time) the "2nd place" tube of choice for Wagner and Grosser, according to what I read on the internet. So I figured I'd go that route, as those two make nice mics. I certainly cannot afford a real VF14.

I've built a couple of mics before, but not from scratch. I put together two of the "Royer mod" MXLs and they came out really really nice. So I'm not a total "rookie" but I do view this project as a "probable learning experience." Hopefully not a "huge waste of money," but sometimes that's how we learn.

I'll slowly amass parts and pieces as budget/funds permit.

Thanks again for the links above. I'll be looking.

zero · Jan 5, 2011

Hi there,

For what i know of the ef12 in a u47, it has a reduced sensitivity and diferent heaters voltage.
i have a Flea with one in it and it is a great sounding microphone(and looking) although i never tried it with a vf14M and probably never will.

cheers

deuce42 · Jan 5, 2011

For what its worth - in my U47 clone I tried both an EF12 and EF14. I preferred the EF12 slightly. It sounded more "hi-fi" - which is a bad way to describe a microphone I think, but it is the world that comes to mind. Pin outs of the EF12 and EF14/VF14 are different. Voltages are different its true.

zero · Jan 5, 2011

Yes, the guys at Flea decribed the ef12 as being a litlle less agressive than the ef14 so more hi-fi is probably the best definition.

soapfoot · Jan 5, 2011

From what I've read, the EF12 was sort of a precursor to the EF86. Can anyone validate?

I'm just hoping to end up with a good-sounding microphone. Sounding 'exactly' like a 'real' U47 is of secondary importance to me; however, I'd like to end up in that "zone."

zebra50 · Jan 5, 2011

From what I've read, the EF12 was sort of a precursor to the EF86. Can anyone validate?

That's what I understood too. . That's where I started out with my STU-47 - I used Max's EF86 circuit and then tweaked (paying attention to heater current and max voltages). Best thing is to look at the data sheets.

e.oelberg · Jan 6, 2011

zebra50 said:
408A also looks like an interesting possibility, 20V heaters IIRC. I have a load but have never really tested them properly in a mic. On the 'to do in 2011' list.

I think jan 6028 is the military version of the 408a

Gus · Jan 6, 2011

What about a solid state circuit?

Insight into "U47-inspired" with EF12 tube?

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