Elam inspired fet mic?

Help Support GroupDIY:

sedit1

Well-known member
Joined
Sep 7, 2011
Messages
73
Location
Finland
I was just browsing through the forum and noticed that Kidvybes mentioned years ago something about 251inspired fet mic.

Does anybody have any clues about this? I noticed that 3u makes something like this in his Warbler mk iv mic.

Would this kind of circuit be much different sounding than
Fet847 or cimilar km84 circuit with good capsule/transformer? I noticed a ami t8 in Kidvybes fet 251.
 

Attachments

  • E501E163-8D97-45FF-AEA8-2B02D1791722.jpeg
    E501E163-8D97-45FF-AEA8-2B02D1791722.jpeg
    547.1 KB · Views: 54

kingkorg

Well-known member
Joined
Apr 15, 2017
Messages
1,243
Location
Norway
This originates from KH, and his Whitney Houston mic. Here's the quote from an interview with him.

You once told me you did a 414-EB for...

For Whitney Houston, but I ELA M'd it.

Really?

It's really a royal pain to modify because there's so little space. But boy, what a pocket rocket. What a killer microphone.

It's using a...

...real CK12, but then a very simple FET design, with not much circuit redundancy, but just a simple FET design, straight out.

What exactly is the ELA M circuit, as found in the Telefunken ELA M 251?
What the ELA M circuit does, in difference to the C12 (which shares the same capsule, tube and transformer as the ELA M-251), is that it has a direct wire connection between the capsule and input of the impedance converter. Whereas the C12 has a coupling capacitor in between, which is already one level of sound degradation. The way the tube is biased is also different in the ELA M and the C12. So you can adapt the better sounding system, even when you have a FET (solid state amplifier). A FET is nothing else but a silicon triode. It's almost the same thing, sonically. Only when it get really loud does the FET show its ugly face. If you stay within moderate sound pressure levels, it's really, really hard to tell the difference between a FET circuit and a tube circuit, if they are otherwise identical in design. Except, there's no noise in a FET circuit. It has always been the sh*tty implementation of FET circuitry that has given FET microphones a bad rap, notably the U87


So you can basically build a u87, ditch the feedback network, capsule/fet coupling cap, and use (or not) lower value of the high value resistors. You need 60v for capsule polarization and of course a true CK12 capsule which is 90% of elam sound. The rest 10% are in order: Capsule grille, high pass created by the capsule and lower value resistors (the biasing of the tube he mentions), 120pF cap plate to ground, and maybe 1% transformer which shouldn't play a big role here.
 

Gus

Well-known member
Joined
Jun 3, 2004
Messages
4,824
Location
n
a thread
https://groupdiy.com/index.php?topic=74723.msg946423#msg946423

"a fet is a silicon triode" is incorrect it is more like a silicon pentode(you could argue it does have a triode like section of the curves but where are JFETs used in the curves)

Another thing in the quote I disagree with. The u87 is not a "sh*tty implementation of a fet circuit"

Transformer does matter if you get the fet circuit right
 

sedit1

Well-known member
Joined
Sep 7, 2011
Messages
73
Location
Finland
Good points!
I was just thinking about fet847 circuit or similar modded ”km84” citcuit and then adding some oscillation board for polarization voltage to ck12...

I think schoeps boards are the only ones with dc/dc converter that I have found but maybe they are too clean sounding.
 

Gus

Well-known member
Joined
Jun 3, 2004
Messages
4,824
Location
n
Look around this site there have been a number of circuits posted over the years that could work. Transformer and transformerless.

 

sedit1

Well-known member
Joined
Sep 7, 2011
Messages
73
Location
Finland
Gus said:
Look around this site there have been a number of circuits posted over the years that could work. Transformer and transformerless.

Thank you, will do  :)
 

AuralArts

New member
Joined
Sep 13, 2021
Messages
2
Location
San Diego
Would the microphone parts T-12 kit be similar to this if the transformer was swapped to the T8?

Did some searching for 12 fet circuit on the forums with various wording and couldn’t find much.

If anyone has found a thread with a circuit that could work for something like that in the op, could you please point me in the right direction?
 

Latest posts

Top