Scott's Telefunken Ela M251E microphone "clone"

I thought I'd take a shot at reproducing a classic. Everyone raves about the Telefunken Ela M251E tube microphone, an it has become one of the most expensive and collectable mics of all time. So why not see if the equivalent can be built? The electronics are not complicated. Here's the schematic. With a transformer from Tab-funkenwork.com, a CK-12 knock-off capsule from Peluso Microphone Lab, some brass parts, and a component or two we'll get jiggy with it!

The grill was made by bending wire mesh around a rolling pin and welding it with plumbers solder and a butane torch.

The hardest part about making a mic like this is not the electronics, but the metal work. Here a rolling pin is used to shape the grill.

I thought that I'd try to make a copy of the Telefunken grill, so I calculated the mesh count by estimating from pictures from the telefunkenusa.com web site.

I believe that the outer mesh has a mesh count of 10 or 11 per inch. I have no way of calculating the mesh count of the inner screen, so I'm using one with a 36 count. This is a much finer mesh, not unlike a screen door.

Here's a closeup of the grill. The interaction between grill and capsule is important. The mesh has a fundamental frequency that is high, so it act like a resonator for frequencies in the 5-10 kHz range. This adds to the perceived brightness of the source that is being recorded.

Brass was used because it is soft and therefore easy to work with. Plumber's solder and a butane torch were used to "weld" the metal.

It would be nice to send this off for chroming. Hmmnnn. Maybe someday.

Brass tubing was used for the body. This is standard 2" brass railing. The nice thing about this diameter is that end plugs can be easily purchased, since they are very common in the 2" size.

I bought a few extra brass rail end plugs and cut them with a hack saw to make some brass rings. These ring will slide up into the tubing, and they help to form the skeleton of the mic body. Electrical grade fiberglass was used to mount the electronics. The fiberglass was cut into rough circles, then glued onto the brass rings.

Brass struts run up three sides of the microphone, which are screwed to the rings. Most of the electronics are mounted directly to the tube socket, as well as up by the polar-pattern selecting switch. I used rivets to tag the components together and to the fiberglass board in turrett board fashion. I really wanted to build a mic the old-fashioned way, with point-to-point wiring (no circuit boards - not that there's anything wrong with that...).

I chose to use high quality components. My feeling is that if you're going to take the time to build something like this, why not spend a lttle more and do it right.

The body is almost done, and it's turning out to be quite big! It's about 6 cm longer than the original (275 mm instead of 215 like the original). This is mainly due to my layout and component choices. The rings still need to be screwed to the brass rails, which will straighten them up. I plan to paint the body, probably an off white color, so that it doesn't look like such a, well, a brass rail! Here are a few more pictures. Next up will be the power supply.

Updated 02/26/2005

Finally, the project is complete! I decided to paint the mic black as pictured below.

The power supply is a cross between the power supply for Jakob Erland's G7 mic and the original power supply for the Ela M251E. There is 120 volts on the plate resistor, and the heaters are run on 6.0 volts DC. I had thought about switching the tube section of the mic upside down to make the leads from the capsule to the tube shorter, but this mic is actually very quiet in terms of self noise. I can't imagine that switching this would make enough difference to make it worth while.

In terms of sound, I can only compare to the less expensive tube mics that I have, which include a Nady TCM 1050 and an ADK Generis. My new mic has a nice, fat sound for closely-miked vocals, and the top end is much smoother than that of my Chinese tube mics. Also, there is less hiss from my new mic than from the others.

I like it. I like it a lot....

I've experimented with adding another layer of fine mesh to the grill . This seems to change the sound in a pleasant way. It cuts some of the wooly, low mids and emphasizes the higher frequencies a bit more. It seems to make my recorded voice sound more natural by reducing some of the unflattering frequencies.

Updated 03/01/2005

Power supply parts list:

silicon diodes x 8
27 kOhm resistor x 3
470 kOhm resitor x 1
470 Ohm resistor
5 kOhm trim pot
47uF 350V electrolytic capacitor x 4
fuse
fuse holder
power switch
LM317K voltage regulator
Triad/Magna TekVPP10-1000 transformer (filament voltage)
Triad/Magna TekVPP12-400 transformer (B+ voltage)
1000uF 35V electrolytic capacitor
10uF 35V electrolytic capacitor
power cord
Hammond chassis 7" x 5" x 2"

Microphone parts list:

CK12 capsule and mount by Peluso Microphone Labs
T314 transformer by Oliver at Tab-Funkenwerk
8 MOhm resistor x 2
1000pF polystyrene capacitor
TPDT on-off-on switch
4800pF capacitor
500 kOhm resistor x 2
30 MOhm resistor x 1
1.8 kOhm resistor x 1
100 kOhm resistor x1
100pF capacitor x 1
3.2 uF capacitor x 1
20 uF electrolytic capacitor x 1

Power supply schematic to follow....

The power supply was built in a Hammond chassis. Neutrik connectors were used.

Power supply guts. The transformers are rotated 90 degrees from one another for minimal interaction.