The other day I was thinking about the design of the ELA M251, and how it differed from the C12 in ways that were intended to make it more Neumann-like - namely, the circuit was simplified and switched to cathode-bias, they changed the pattern control to an on-mic switch (like the U47), they used a larger, more Neumann-esque headbasket, and they added a cap from plate to ground to tame the top end (presumably to make the CK12 sound slightly more like an M7). The non-export version even used an AC701K, a tube that the M49 used.
Side note: does anyone know what the letters in the model name "ELA M251" stand for? I know the suffix "e" is for export (denoting a 6072 instead of the AC701K), but I have no idea what "ELA" or "M" stand for.
Anyway - I suddenly thought about the modern Chinese "CK12" capsules, and how they're just edge-terminated K67 capsules, and had the thought, "ha, seems like something Telefunken might have commissioned after the release of the U87i."
So I went down a rabbit hole...
The Neumann KM series was their first foray into solid state (the 'KTM' came out in 1965), and the U87i followed two years later, in 1967. As far as I can tell, the U87i became an instant hit, and Telefunken must have wished they had an answer for it. AKG didn't transistorize their C12a until ~1971 (calling it the C412).
There's a gap there, that could have been filled with my fictional mic...
In 1968, Telefunken approached AKG to design and manufacture a mic to go head-to-head with the U87i. It needed to share DNA with the ELA M251 that had become famous, but it had to be transistor-based (ideally a similar circuit to what Neumann used), needed to be powered by P48, and needed to be good for vocals (where microphones become famous).
So...the engineers at AKG got to work. They were impressed by Neumann's new K67 capsule and how much easier it was to produce than their own CK12, but they wanted to retain the comparative "flat" sound of their edge-terminated design, so they put an edge-terminated diaphragm on a K67-style backplate. Now to design a circuit to put it on...
While the U87i circuit was a good starting point, their new capsule didn't share the high-frequency lift of the K67, so the de-emphasis wasn't needed. They could use the KM84 circuit (a great new mic that had just been released two years prior), but they wanted to do something to keep a sense of "warmth" in the sound and voice it a little closer to the U87i - the solution was obvious - add a small capacitor from the drain of the FET to ground, similar to the plate-to-ground cap in the 251! The output transformer would be something of a cross between their beloved T14/1 and Neumann's Bv.13 (the best modern approximation of this might be a Cinemag 2480). The resulting circuit:
(Cardiod-only for now, more on that later)
The housing would be like the ELA M251, but smaller (something like the modern "GT-2B" body), and it would be painted in the 251 colors.
Side note: does anyone know what the letters in the model name "ELA M251" stand for? I know the suffix "e" is for export (denoting a 6072 instead of the AC701K), but I have no idea what "ELA" or "M" stand for.
Anyway - I suddenly thought about the modern Chinese "CK12" capsules, and how they're just edge-terminated K67 capsules, and had the thought, "ha, seems like something Telefunken might have commissioned after the release of the U87i."
So I went down a rabbit hole...
The Neumann KM series was their first foray into solid state (the 'KTM' came out in 1965), and the U87i followed two years later, in 1967. As far as I can tell, the U87i became an instant hit, and Telefunken must have wished they had an answer for it. AKG didn't transistorize their C12a until ~1971 (calling it the C412).
There's a gap there, that could have been filled with my fictional mic...
In 1968, Telefunken approached AKG to design and manufacture a mic to go head-to-head with the U87i. It needed to share DNA with the ELA M251 that had become famous, but it had to be transistor-based (ideally a similar circuit to what Neumann used), needed to be powered by P48, and needed to be good for vocals (where microphones become famous).
So...the engineers at AKG got to work. They were impressed by Neumann's new K67 capsule and how much easier it was to produce than their own CK12, but they wanted to retain the comparative "flat" sound of their edge-terminated design, so they put an edge-terminated diaphragm on a K67-style backplate. Now to design a circuit to put it on...
While the U87i circuit was a good starting point, their new capsule didn't share the high-frequency lift of the K67, so the de-emphasis wasn't needed. They could use the KM84 circuit (a great new mic that had just been released two years prior), but they wanted to do something to keep a sense of "warmth" in the sound and voice it a little closer to the U87i - the solution was obvious - add a small capacitor from the drain of the FET to ground, similar to the plate-to-ground cap in the 251! The output transformer would be something of a cross between their beloved T14/1 and Neumann's Bv.13 (the best modern approximation of this might be a Cinemag 2480). The resulting circuit:
(Cardiod-only for now, more on that later)
The housing would be like the ELA M251, but smaller (something like the modern "GT-2B" body), and it would be painted in the 251 colors.
