Telefunken ELA M 251 Clone Tube Microphone Build Thread (D-Ela M 251E)

[poctop]

Dear Lauritz/PhatplanetStudio,

congratulations you have a near perfect Elam 251 plot : see the original plots at http://recordinghacks.com/pdf/telefunken/ElaM-250-251-Manual.pdf , 

you're near the specs...

but if u want to be sure , double check B+ with the mic plugged : max 110V , check the heater : 6.3V , check that all the HiZ sections are perfectly cleaned , check the capsule voltage before the 8Mohms resistors : around 60V

If your capsule is a bit low end shy for your taste, try to decrease capsule voltage to 55V (reduce the 0.5MOhms to ground),  increase the 30Mohms grid resistor to 300Mohms and put a 100uF on the cathode instead of 22uF. U could increase the output coupling capacitor up to 3.3uF as well ....

with the high end response, assuming your plot is accurate , i would increase the output LP filter by increasing the 120pF to 220pF or even 330pF ... (or more to taste)

regards
Fred

Thanks a lot for your thoughts on the matter...i see now from the schematic that there is a 100k resistor on the way to the anode. With approx. 0,5mA current it leads to a 50V voltage drop, so i guess 160V is more than low enough -measuring directly at the output of the power supply.

Another quick question...i am saving up money for a Tim Cambell capsule, so i don't have a capsule yet. Would there be any problems just putting in 2 capacitors with electrical equivalent values( as the capsule ) and do circuit checks like that? Do i even need that, or could i just power up the mic without the capsule installed?


thanks

best
Lauritz

Thanks a lot for your thoughts on the matter...i see now from the schematic that there is a 100k resistor on the way to the anode. With approx. 0,5mA current it leads to a 50V voltage drop, so i guess 160V is more than low enough -measuring directly at the output of the power supply.

Not Really , you need the output from the psu when the mic is connected and loaded to be 110V,
you cannot account for this with the plate resistor , cause everything parameter on the bias and plate will be off
the best way to do this is to emulate a dummmy load with calculating the resistor required to test it under load wihout the need of the mic both for heaters and B+  , this way you dont over blow the tube , if you have a little higher voltage you can increase a little more R1 and R2
Best,
Dan,

 

[lauritz]

Not Really , you need the output from the psu when the mic is connected and loaded to be 110V,
you cannot account for this with the plate resistor , cause everything parameter on the bias and plate will be off
the best way to do this is to emulate a dummmy load with calculating the resistor required to test it under load wihout the need of the mic both for heaters and B+  , this way you dont over blow the tube , if you have a little higher voltage you can increase a little more R1 and R2
Best,
Dan,

Ok Dan, thanks for the correction I will sit down and have a thorough look at the schematic soon, and try the dummy load test you suggest. It surprises me that no one asked about this earlier in this thread...but i guess it's just me who's a beginner, or maybe just overly concerned about the wellbeing of the components 8)

best
Lauritz

 

[kosi]

Hi Dan, I'm located in europe.
would this toroidal work ?

http://www.tube-town.net/ttstore/Transformer/Power-Transformer/Toroidal/Toroidal-30VA::2192.html?language=en
Pri: 0 - 220 - 230 - 240 V (black-yellow-purple-red)
Sec 1: 200 V @ 0,1 A (red )
Sec 2: 6,3 V @ 1,5 A (green)

It'a the same, that I used for the PSU of the MKU47

thanks

 

[kosi]

Could anybody tell me: 
which XLR connector uses the BeesNeez Bodykit ?

thanks 

 

[Banzai]

Standard 7-pin XLR insert.

Could anybody tell me: 
which XLR connector uses the BeesNeez Bodykit ?

thanks 

 

[PhatPlanetStudios]

Our Baby is born!  Our Elam 251 clone lives and breathes!  Thanks so much to poctop, our gracious host to this journey into microphone history!  I couldn't have done it without him, he's such a great engineer, great help, and is super cool! 

It turned out to be a fabulous sounding mic and it was just recently used on a word-class opera recording.  The build was great, and it worked from the get-go.  A little tweaking was done, and then we were ready to put it to work.  It was stressful before we got the approval of artist and engineers, but now a great joy that it's been accepted by the pros.  There was a mic shootout between Brauner VM1 and Bock 251, and our DIY Elam 251 beat them both. 

Here's the specs;
PCB:  vintagemicrophonepcbkit.com
Body & head basket:  Beesneez
Capsule:  Beesneez
Transformer:  AMI
Tube:  NOS GE 5-star
All Silver Solder used
PSU Cable: Gotham audio
Internal wiring:  Silver coated copper, teflon jacket
Components:  Mouser & VM-PCBkit

You may look at the build photos and WAV samples of the mic shootout.  Note they're dry WAV files.  Add reverb for max enjoyment....
https://www.dropbox.com/sh/rysai5anrce6ota/AABnr3CkU_fPXH0U1Cy9UNH-a?dl=0

 

[Matt55]

Hello PhatPlanet Studios,

Lovely build, sounding mic and singer!!  I am looking to build one myself maybe with a few slightly different components.

I noticed you mentioned the mic needed some tweaking. I wondered if you could be a bit more specific? I noticed granger.frederic made some pointers in post #206 did you use any of them for tweaking or was it other things?

Did the frequency plot look different once you had finished tweaking?

Thanks for your time,

Regards,

  Matt

 

[PhatPlanetStudios]

Hello Matt,
Thanks for the compliment!  After the initial build and sweep test, the mic was shy in the bass for our taste.  It dropped significantly below 200hz.  I got some great advice from Dany and I ended up changing the tantalum (C3) to a 100mF.  I then ran a sweep test and it appeared to improve the bass response nicely.  I had intention to change out the large cap (C1), but never found the time to setup the sweep test (before and after).  We then had to go into using the mic on the session.  After hearing the result, I haven't gone back in for additional mods.  I think I'll build another mic so I can run some further tests.  This mic is making everyone happy around here, so i don't want to mess it up!

Hello PhatPlanet Studios,

Lovely build, sounding mic and singer!!  I am looking to build one myself maybe with a few slightly different components.

I noticed you mentioned the mic needed some tweaking. I wondered if you could be a bit more specific? I noticed granger.frederic made some pointers in post #206 did you use any of them for tweaking or was it other things?

Did the frequency plot look different once you had finished tweaking?

Thanks for your time,

Regards,

  Matt

 

[Gijsvanwel]

Hello fellow builders,

I just finished my build and it sounds awesome!

Specs:
Peluso cek12
Cinemag cm 13114
NOS ge jan 6072a

Im getting very loud pops when using The pattern switch (with preamp gain turn to 0 it still clips) Is there any way to ground the pattern switch or should i just set it to the pattern i want to use before turning on the psu?

My b+ and heater voltages are 110v and 6.3v measured in the mic.

Any help would be much appreciated.

 

[poctop]

Hello fellow builders,

I just finished my build and it sounds awesome!

Specs:
Peluso cek12
Cinemag cm 13114
NOS ge jan 6072a

Im getting very loud pops when using The pattern switch (with preamp gain turn to 0 it still clips) Is there any way to ground the pattern switch or should i just set it to the pattern i want to use before turning on the psu?

My b+ and heater voltages are 110v and 6.3v measured in the mic.

Any help would be much appreciated.

a Thump when switching pattern is totally normal.
Best,
Dan,
Thanks for posting ,
BEst,
Dan,

 

[o3misha]

I am confused...According to schematic you have to get 120 VDC on the 100k resistor.

http://recordinghacks.com/pdf/telefunken/ElaM-250-251-Manual.pdf

Guys, original Haufe t14/1 has 11,5:1 ratio. I saw the document from Haufe.

 

[stevesteve50]

Hello,

I ordered the styroflex capacitor kit with my PCB through vintagemicrophonepcbkit.com. I received one  labeled 1000J 630V, and two labeled 5000J 630V. The package had C12 written on it, though i had ordered for the D-251 build. Is it possible that I was sent the film capacitors for the C12 instead of the 251? What options do I have in getting the correct parts if so?

Steve

 

[poctop]

Hello,

I ordered the styroflex capacitor kit with my PCB through vintagemicrophonepcbkit.com. I received one  labeled 1000J 630V, and two labeled 5000J 630V. The package had C12 written on it, though i had ordered for the D-251 build. Is it possible that I was sent the film capacitors for the C12 instead of the 251? What options do I have in getting the correct parts if so?

Steve

Please send me by PM you Order Number of Paypal I will check your order and validate this ,
Yes this is the C12 Styros Kit indeed,

 

[stevesteve50]

Hi Folks,

I finished soldering up the mic last night. I double checked voltages before I hooked up the capsule. I'm doing all testing on a chinese capsule w a single backplane before I hook up the Tim Campbell. Here's the issue I'm having:

There is a very loud hum/buzz that is much louder than any of the audio passing through. It is not a specific frequency, but a broad range. It sounds like putting your finger on the end of a guitar cable plugged into an amp.

Audio does pass through on omni and cardiod modes. Audio does not pass through on figure 8 mode. (buzz in constant on all modes)

I have been trying to find a thread that would help me troubleshoot the issue but haven't found one yet. I was hoping that someone could either point me in the direction of a thread that covers this issue, or perhaps help troubleshoot.

Many thanks!

Steve

 

[tonzauber]

Do you have the circuit in the housing when you test it? Else it will be just a giant rf receiver...

Make sure that all your housing connections are fit tightly, so that you have a good ground connection.

If the microphone works in cardioid and omni, there is no reason that it should not work in figure of eight as well. Measure the voltages that show up on the back diaphragm connection. In Fig.8 it should be 120V, in Cardioid 60V, in Omni 0V.

I had something similar, but it did work in omni only - no pattern switching at all. It was a cold solder joint in the path of the polarization voltage of the backplate.

 

[chefducuisine]

Steve,

to me this sounds like if you are testing the mic with the housing / body tube removed and or without the headbasket.
Another reason could be a missing ground connection.

Edit: Just saw 'tonzauber' was a bit faster with a similar suggestion...

 

[duantro]

Yeah, I'd double check the relay wiring if it isn't working in fig 8. May have something switched up here.
On a side note, this mic sounds amazing with an ac701 tube!

 

[stevesteve50]

Do you have the circuit in the housing when you test it? Else it will be just a giant rf receiver...

Thanks! I didn't realize the rf it would pick up would be that drastic.  :-[ Issue solved.

If the microphone works in cardioid and omni, there is no reason that it should not work in figure of eight as well. Measure the voltages that show up on the back diaphragm connection. In Fig.8 it should be 120V, in Cardioid 60V, in Omni 0V.

The mic seems to be working fine in both cardiod and omni now, however, voltages on the rear capsule are as follows:
Fig.8 22.3 VDC, Cardiod 0VDC, Omni 32VDC

The front of the capsule is constant at 32VDC
The plate voltage varies between 59-62VDC depending on the pattern
B+ is set to 120
Heater is set to 6.2

The patterns are wired and respond correctly, but the voltages aren't matching up. What could be going on?

Correct me on my first post. When I select the Fig.8 pattern, there is almost no signal at all that can be heard except a very faint hum. I'm using a chinese capsule with a single backplate. I've connected the backplate on the capsule to both the "front" and "rear" backplane terminals on the mic pcb. Could this have something to do with the issue? The relays K1 and K3 are receiving 6.3 when the Fig.8  switch is engaged

Thanks again for the help!

Steve

 

[chefducuisine]

Hi Steve,

you cannot measure voltages on the capsule directly as you are in the high impedance section of the microphone.
In other words: The input resistance of your Multimeter is loading down the voltages resulting in the values you measure.

Plate voltage, heater and B+ look OK to me.

For the 251 you'll need a capsule with separate backplates, otherwise Figure of Eight won't work. Check the upper right part of the schematic named 'Kapsel f. ELA M251E'.
http://www.xaudia.com/xaudia/Schematics/Pages/ELAM_files/Media/m251e/m251e.jpg

Summary:
Congratulations - you have a working 251 !!! 8)
At the moment you are limited by the capsule itself (loosing Figure of Eight).
Remove it and get a good one - this mic deserves it!

(I recommend Tim's CT-12, BeezNeez also has a nice one - check the white market).

 

[kidvybes]

I'm not yet certain, but it looks as though Blackspade Audio may be offering their new custom 251-inspired body for sale for kit use, apart from the finished/built version RS-series mics...here's some pics...