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

[Carnesd]

Carnesd it sounds like you reversed your backplate connections , have a short between your backplates most likely within the capsule or your backplate connections are shorting against each other.

You are the man Tim,  I swapped the backplate wires and now its working correctly.  I guess I'm a little confused on why the backplates are hooked up the way they are, you would think the front BP would be closest to the front membrane.  I guess I'm a little confused on whats going on inside the capsule and I couldn't seem to find a good diagram of how to hook up the c12 type capsule. 
Thank you for your help. 

 

[jbassino]

I built this Clone some time ago with Campbell's capsule. Overall the mic sounds excellent but I only find it too silibant in the 8-12k area, almost with any singer.

I'm wondering if anyone had this similar issue and what tweaks worked best!

Thanks

 

[LeFinbongo]

What about your audio pair inside the power supply? Twisted? Short? Avoids filter caps?

Wow. thank u for that comment! I gave up on my ELA nearly a year ago when I just couldn't figure out why it was so noisy and turns out all it needed was some twisting. Now its perfect!  :´D

 

[micaddict]

Welcome and congrats. 


BTW why didn't you ask for help a year ago?

 

[LeFinbongo]

Read through replies to people with similar problems. After troubleshooting for a long time I guess I just assumed it would be no quick fix and that I'd need hands on assistance. Something I never got around to...

 

[SparkleBear]

(Probably should have just posted this here in the microphone thread, apologies)

Greetings All,

I've been on and off trying to track down the white noise in my D-251 build for about a year now. I have noise tested the 6072a and its super quiet, Replaced the CT12 capsule, de-soldered the whole thing, cleaned it, re-soldered it up again, changed the output caps, twisted the audio wires in the power supply and kept them from the filter caps, tried filtering the B+.... all to no avail. The white noise makes it pretty un-usable for any voiceover/vocal or acoustic guitar application as the hiss is too noticeable.  I am going to post a few sample recordings, perhaps anyone has any ideas. Listen to the lead in before the guitar comes in... I am posting a recording with my D251 and next with my MK Audio U67. The 67 is dead quiet in the lead in...

251 link: https://www.dropbox.com/s/doga2sonunml4u6/Will%20She%20Be%20Gone%20%28251%29.mp3?dl=0

u67 link: https://www.dropbox.com/s/1dmqcloash2avqx/Will%20She%20Be%20Gone%20%28u67%20no%20filters%29.mp3?dl=0

Ideas Anyone?

I am out of them... Perhaps there is a qualified technician who may be able to troubleshoot this on their bench for a fee? Anyone out there servicing DIY microphones? Any help is so appreciated.

Thanks a ton!

 

[ShaneSBG]

(Probably should have just posted this here in the microphone thread, apologies)

Greetings All,

I've been on and off trying to track down the white noise in my D-251 build for about a year now. I have noise tested the 6072a and its super quiet, Replaced the CT12 capsule, de-soldered the whole thing, cleaned it, re-soldered it up again, changed the output caps, twisted the audio wires in the power supply and kept them from the filter caps, tried filtering the B+.... all to no avail. The white noise makes it pretty un-usable for any voiceover/vocal or acoustic guitar application as the hiss is too noticeable.  I am going to post a few sample recordings, perhaps anyone has any ideas. Listen to the lead in before the guitar comes in... I am posting a recording with my D251 and next with my MK Audio U67. The 67 is dead quiet in the lead in...

251 link: https://www.dropbox.com/s/doga2sonunml4u6/Will%20She%20Be%20Gone%20%28251%29.mp3?dl=0

u67 link: https://www.dropbox.com/s/1dmqcloash2avqx/Will%20She%20Be%20Gone%20%28u67%20no%20filters%29.mp3?dl=0

Ideas Anyone?

I am out of them... Perhaps there is a qualified technician who may be able to troubleshoot this on their bench for a fee? Anyone out there servicing DIY microphones? Any help is so appreciated.

Thanks a ton!

I have no idea if this will help you or not, but I was talking with a few people a few months ago about noisy 408a tubes and it seems the noise was from a binder connector...again, no clue if this will help, but check this out and maybe. I don't know what type of connector you have...hope it helps

https://groupdiy.com/index.php?topic=66062.40
we were talking about it here and specifically reply/post 42
http://prorecordingworkshop.lefora.com/topic/19405924/EF800-as-a-microphone-tube-issues?page=1#.WWPwAulpyM8
read until post 43

 

[ComplicationFetish]

So, I finished this build and I love it (my first successful mic build)! 

Now, I'm looking into implementing some of the suggestions to modify the low end response.  I am a noob when it comes to electronics, but if I wanted to slightly increase the cap value of C1 (or any cap), but still wanted to maintain the use of my original cap, can I simply add an additional cap, wired in parallel with the first cap, or am I thinking of this wrong, or would there be unwanted consequences to the sound that I am not aware of?

 

[snaredrum]

Hi i try to built this elam,  first i had built a c12 copy and it work well,  but i dont understand all the indication on mic pcb.  S+ s-  p+ p-  a+ a- i have a small idea but i am not sûre.  Can i get more info for plug right from the t14 and xlr 7 pin thanks

 

[Delta Sigma]

See Trans4funks1's diagram: P = primary, S = secondary; +/- for polarity.

https://cdn.groupbuilder.com/groupdiy/u/39511/58d1402a06461.pdf

A+ and A- must be audio out to your mic cable. Check with ohmmeter. A+ and S+ (also A- and S-) should have continuity.

 

[a.payne]

I'm currently building an ELA M 251 and had a beginner question regarding the point to point between the pattern switch, 7 pin xlr and 3 pin xlr.

I have added the link to a really sketchy diagram of how i think it should look based on the wiring i saw on Dans PSU. I just got confused because it seemed a little different to the PSU diagram uploaded with the original post.

https://drive.google.com/open?id=15UNCnW2NtRvbosZPzj_aF0fmjHR9aDbl

It would be great if someone could let me know if it's going to work or not
Best,
ali

 

[Zebra_PD]

What tubes would u guys recommend/prefer for this build if you tried some different ones?

What sonic difference have you experience with different tubes?

For example NOS Telefunken or NOS GE 12au7/ecc82/6072? Perhaps even some other brand/model?

 

[tonycamp]

What tubes would u guys recommend/prefer for this build if you tried some different ones?

What sonic difference have you experience with different tubes?

For example NOS Telefunken or NOS GE 12au7/ecc82/6072? Perhaps even some other brand/model?

1950’s Nos GE 6072 5-star tested for low noise/microphonics, the red/orange ink if u can get it.

 

[Gus]

(Probably should have just posted this here in the microphone thread, apologies)

Greetings All,

I've been on and off trying to track down the white noise in my D-251 build for about a year now. I have noise tested the 6072a and its super quiet, Replaced the CT12 capsule, de-soldered the whole thing, cleaned it, re-soldered it up again, changed the output caps, twisted the audio wires in the power supply and kept them from the filter caps, tried filtering the B+.... all to no avail. The white noise makes it pretty un-usable for any voiceover/vocal or acoustic guitar application as the hiss is too noticeable.  I am going to post a few sample recordings, perhaps anyone has any ideas. Listen to the lead in before the guitar comes in... I am posting a recording with my D251 and next with my MK Audio U67. The 67 is dead quiet in the lead in...

251 link: https://www.dropbox.com/s/doga2sonunml4u6/Will%20She%20Be%20Gone%20%28251%29.mp3?dl=0

u67 link: https://www.dropbox.com/s/1dmqcloash2avqx/Will%20She%20Be%20Gone%20%28u67%20no%20filters%29.mp3?dl=0

Ideas Anyone?

I am out of them... Perhaps there is a qualified technician who may be able to troubleshoot this on their bench for a fee? Anyone out there servicing DIY microphones? Any help is so appreciated.

Thanks a ton!

Have you substituted a fixed cap for the capsule and checked for the noise?
Something else to think about is the tube socket, how clean is it? I have ultrasonic cleaned tube sockets.

How did you noise test the 6072a? Did you build a microphone circuit fragment using the same value grid resistor and place it in a metal shielding box and listen to it?

 

[bancho]

I want to use toroidal tx for the PSU. What are the required current values for the secondaries? Are these correct / would these be ok?
200V - 0.1A 
9.5V - 0.5A
I searched the forum "million" times but couldn't find the answer (there are just few posts by kosi which were never answered)
Thanks!

 

[poctop]

I want to use toroidal tx for the PSU. What are the required current values for the secondaries? Are these correct / would these be ok?
200V - 0.1A 
9.5V - 0.5A
I searched the forum "million" times but couldn't find the answer (there are just few posts by kosi which were never answered)
Thanks!

Secondary: 200VAC @ 10mA (~2VA)
Secondary: 9.5VAC @ 500mA (~5VA)

yes they would ,
best ,
D.

 

[rmburrow]

Have you substituted a fixed cap for the capsule and checked for the noise?
Something else to think about is the tube socket, how clean is it? I have ultrasonic cleaned tube sockets.

How did you noise test the 6072a? Did you build a microphone circuit fragment using the same value grid resistor and place it in a metal shielding box and listen to it?

Good suggestions.  Is the noise still present immediately after the AC is turned off to the P/S yet the capacitors still hold charge?  Have you tried a battery supply (4 D cells in series for heater,  twenty 9 volt batteries in series for the HT?

Is this mic being used near (3 km or so) any known FM radio or TV transmitter locations?  One would hear the audio if RF interference (" RFI")  was from an AM station.  Over the air FM radio and digital television use different modulation techniques, but the microphone circuits can rectify the offending signal and create noise in the microphone.  Some mic manufacturers put a small ferrite bead between the capsule and the grid of the tube for RF suppression.    In any event, it is imperative that all metal work of the mic case including the head basket, screens, shields, etc. be thoroughly and electrically bonded together to minimize RFI problems.    The next problem area can be the mic to P/S cable.  Poor solder joints or unintentional ground loops result in hum or other noise.

Last but not least:  Is the output transformer correctly wired?  Does the primary or the secondary of the output transformer contain "split" windings that require interconnecting jumpers in addition to the usual input and output connections?  Forgetting the jumpers (if required) can rack up hours of troubleshooting time...  Do not give up; troubleshooting noise can be a "tough dog" problem.

Be careful when working around dangerous voltages associated with vacuum tube microphones.

 

[snaredrum]

Secondary: 200VAC @ 10mA (~2VA)
Secondary: 9.5VAC @ 500mA (~5VA)

yes they would ,
best ,
D.

i try to find a new transfo for my apex PSU and it's very difficult ,  i look for  tips and make my own transformer )

 

[Zebra_PD]

1950’s Nos GE 6072 5-star tested for low noise/microphonics, the red/orange ink if u can get it.

The 6072 seems like the most logic choice since it was the original ones for the export version. But I haven't been able to located a good source for them in Europe. Any tips of a european store/source that not is extremely over priced and/reliable?

Otherwise has anyone used a high quality telefunken/phillips  tube like a ECC802 in there mic builds? They seem to be easier to find here in Europe?

 

[snaredrum]

i try to find a new transfo for my apex PSU and it's very difficult ,  i look for  tips and make my own transformer )

i have found in france for 17 euros a hand made transfo , i order 2 )))