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

[koki]

I went down to 680nF with the DC blocking capacitor because anything over 1µF was way too bass heavy in my opinion. Then I got the warm mids that were there into focus. As for the tube, I'll be honest - I've tried lot of tubes, built "triode switch" adapters between the tube and socket to test both triodes on the tubes, and burned them in for days. There are only two "available" NOS tubes that I think have that "expensive" sounding, direct character. They are the 5-star Mica GE6072 and the Siemens Halske ECC801S. There are a lot of noisy/crackly NOS GE6072s on the market though and they are all expensive. It can be an expensive and educational journey until you find the right one. All other tubes sounded dull, not detailed/washed out, lacked warmth, no character or were too loud. And the TF AC701 is more a expensive Lottery nowadays.The GE6072 has that sexy edge, is perfectly balanced, hard to explain. It's magical. The Siemens Halske mentioned is also excellent and more available, less noise, very proud sound. TF ECC801S were good but a bit too much noise.

Thanks, ill try that. What is yours grid resistor value ?

 

[HerbertR]

100M Ohm on the Grid to Ground, on the Kathode 22uF and 1.8k Ohm. Regards

 

[Delta Sigma]

I think it's time to cut the counterfeit discussion out of this thread. If someone feels the need to keep it going, another thread would be useful. It's starting to bury the build thread.

 

[TLRT]

I went down to 680nF with the DC blocking capacitor because anything over 1µF was way too bass heavy in my opinion. Then I got the warm mids that were there into focus. As for the tube, I'll be honest - I've tried lot of tubes, built "triode switch" adapters between the tube and socket to test both triodes on the tubes, and burned them in for days. There are only two "available" NOS tubes that I think have that "expensive" sounding, direct character. They are the 5-star Mica GE6072 and the Siemens Halske ECC801S. There are a lot of noisy/crackly NOS GE6072s on the market though and they are all expensive. It can be an expensive and educational journey until you find the right one. All other tubes sounded dull, not detailed/washed out, lacked warmth, no character or were too loud. And the TF AC701 is more a expensive Lottery nowadays.The GE6072 has that sexy edge, is perfectly balanced, hard to explain. It's magical. The Siemens Halske mentioned is also excellent and more available, less noise, very proud sound. TF ECC801S were good but a bit too much noise.

Siemens triple mica tubes usually sounds too dull/dark for mics, I use them for phase inverters only. Mullards are usually the opposite, too bright. Agree about the 6072/ac701 most of them are not mic grade on the market (luckily I still have many of them

 

[HerbertR]

Siemens triple mica tubes usually sounds too dull/dark for mics, I use them for phase inverters only. Mullards are usually the opposite, too bright. Agree about the 6072/ac701 most of them are not mic grade on the market (luckily I still have many of....

Yes, a couple of 701s would be really sexy. But I don't play the lottery, so I wouldn't try to buy from unknown sellers (not you....)

Personally, I think these "very rare" Siemens Halske triple Mica ECC801S with the brand/label sound pretty good (the ones with the two holes on the plate side and the round getter and the shield mica over the top/finger mica, I think it was the German Military Version). Most other Siemens ECC81s... are total junk, like the DDR models. In my opinion, these Siemens Halske ECCs sound a bit brighter and also have a bit more low end than the more roundly balanced GE6072s. I have 11 NOS GE6072s and 6 of them are unusable, both triodes of them. They crackle or have a higher noise floor. Of the 6 Siemens Halske ECC801S NOS tubes, 4 are excellent, two are also unusable for microphones, they also crackle. One thing is really great, the Siemens Halske clearly have a better background noise compared to the "good" GE6072. That's my opinion.

 

[paulcheeba]

Has anyone used Haun CK12's in one of these builds? I'm wondering how the connections attach compared to a Beesneez etc?
Also has anyone had problems with Figure of 8 cutting out altogether?

 

[Tim Campbell]

Has anyone used Haun CK12's in one of these builds? I'm wondering how the connections attach compared to a Beesneez etc?
Also has anyone had problems with Figure of 8 cutting out altogether?

All CK12 clone capsules are set up the same including Haun's. The backplate connection of each half is on the same side as it's corresponding membrane. The 251 polarization scheme requires that the 2 halves of the capsule are electronically insulated from each other and any debris at all between backplates or the backplate solder tags touching each other will cause a short. If your capsule is cutting out completely you are making a direct short at either the capsule or it could be in the wiring at your pcb.

 

[paulcheeba]

Thanks Tim. Just seems weird it’s happening on both mics exactly the same. I’m not convinced about these relays.

 

[paulcheeba]

All CK12 clone capsules are set up the same including Haun's. The backplate connection of each half is on the same side as it's corresponding membrane. The 251 polarization scheme requires that the 2 halves of the capsule are electronically insulated from each other and any debris at all between backplates or the backplate solder tags touching each other will cause a short. If your capsule is cutting out completely you are making a direct short at either the capsule or it could be in the wiring at your pcb.

The Haun I have has a single solder tag that seems to connect both plates.

 

[Tim Campbell]

The Haun I have has a single solder tag that seems to connect both plates.

There is your problem right there. The backplates cannot be connected to each other in this kind of polarization scheme

 

[thomasdf]

Yes, a couple of 701s would be really sexy. But I don't play the lottery, so I wouldn't try to buy from unknown sellers (not you....)

Personally, I think these "very rare" Siemens Halske triple Mica ECC801S with the brand/label sound pretty good (the ones with the two holes on the plate side and the round getter and the shield mica over the top/finger mica, I think it was the German Military Version). Most other Siemens ECC81s... are total junk, like the DDR models. In my opinion, these Siemens Halske ECCs sound a bit brighter and also have a bit more low end than the more roundly balanced GE6072s. I have 11 NOS GE6072s and 6 of them are unusable, both triodes of them. They crackle or have a higher noise floor. Of the 6 Siemens Halske ECC801S NOS tubes, 4 are excellent, two are also unusable for microphones, they also crackle. One thing is really great, the Siemens Halske clearly have a better background noise compared to the "good" GE6072. That's my opinion.

I have a bunch of these EC801S in my stock, maybe 6 or something like that and intended to use them in my 251 pair. Did you do any mod to the circuit in order to use them instead of the orig tube ? Thanks

 

[paulcheeba]

There is your problem right there. The backplates cannot be connected to each other in this kind of polarization scheme

So they're not all the same.

 

[Tim Campbell]

So they're not all the same.

The capsules are all the same. How they connected by solder tags is different. If you remove this bridge and connect each backplate separately it should work the same as Ben's or any other CK12 copy. None of the Haun capsules I own came with bridged backplates so it seems yours were wired for the type of polarization used in C12, C12a, 414, etc.

 

[paulcheeba]

The capsules are all the same. How they connected by solder tags is different. If you remove this bridge and connect each backplate separately it should work the same as Ben's or any other CK12 copy. None of the Haun capsules I own came with bridged backplates so it seems yours were wired for the type of polarization used in C12, C12a, 414, etc.

Okay thanks again, will it be fine if I remove the tag and replace it with individual tags?

 

[HerbertR]

I have a bunch of these EC801S in my stock, maybe 6 or something like that and intended to use them in my 251 pair. Did you do any mod to the circuit in order to use them instead of the orig tube ? Thanks

Hi, the ECC801S is a direct replacement without any modifications required. As I said, I am referring to the rare Siemens Halske ECC801S tube. You can identify/compare your ECC8xx tube here.
https://jacmusic.com/nos/ECC81.htm
The best Version, the original, extremely rare Telefunken 801S costs much more than an excellent GE 6072 nowadays.


Regarding Figure8 in 251 - I had problems with short circuits of the backplates in CK12 and K87 Style Capsules caused by long and rough deliveries. My capsule blackplates were not "bridged" at the factory. The insulation between the two capsule halves especially in CK12 Style Capsules is very, very thin and was "short" through bumps ...via Post or what else... when delivered. I was able to solve the problem by slightly loosening the three connecting screws that hold the two halves together, one by one, and immediately re-tightening them, and checking the conductivity between the two backplates until the conductivity disappeared and then only opening the problematically screw as far as really necessary. I am anything but a specialist and it is a very demanding / precise job. So I don’t want to encourage anyone who is afraid to undergo such an operation. But it can be fixed in about a minute, and is super easy. Arienne gave me the instructions for K87 capsules, the same works for Ck12s she is a great person...

 

[paulcheeba]

Hi, the ECC801S is a direct replacement without any modifications required. As I said, I am referring to the rare Siemens Halske ECC801S tube. You can identify/compare your ECC8xx tube here.
https://jacmusic.com/nos/ECC81.htm
The best Version, the original, extremely rare Telefunken 801S costs much more than an excellent GE 6072 nowadays.


Regarding Figure8 in 251 - I had problems with short circuits of the backplates in CK12 and K87 Style Capsules caused by long and rough deliveries. My capsule blackplates were not "bridged" at the factory. The insulation between the two capsule halves especially in CK12 Style Capsules is very, very thin and was "short" through bumps ...via Post or what else... when delivered. I was able to solve the problem by slightly loosening the three connecting screws that hold the two halves together, one by one, and immediately re-tightening them, and checking the conductivity between the two backplates until the conductivity disappeared and then only opening the problematically screw as far as really necessary. I am anything but a specialist and it is a very demanding / precise job. So I don’t want to encourage anyone who is afraid to undergo such an operation. But it can be fixed in about a minute, and is super easy. Arienne gave me the instructions for K87 capsules, the same works for Ck12s she is a great person...

Thanks Herbert super useful advice as usual.

 

[Tim Campbell]

Okay thanks again, will it be fine if I remove the tag and replace it with individual tags?

Yes. There should be 4 wires coming to the capsule. As long as they are connected to the correct terminal the capsule should work properly if there is no debris between the capsule backplates.

 

[geekmacdaddy]

With the help of HerbertR's photos and this thread, I'm done with mine, and it's sounds crazy good. A 3C Transformer (again, HerbertR's report about too much bottom led me there, and I'm glad), Beesneez Capsule, I'm happy, but there's one issue and a question. What pins on the rotary switch (besides the center) are used? When the polarity switch is all the way to the left, the mic sounds as it should. Middle and right sound like a burnt styroflex, but they are fine, so I suspect the wiring. Now the question; I dialed in 120v, and 6.3v. Is there no way to set the Bias or is it self biasing? Where do you take that reading? Thanks in advance, and damn. I waited sooooooo long from all the international suppliers, but when it comes together, you aren't thinking about the wait.

 

[geekmacdaddy]

Bit of capsule wiring problem that is now fixed! (only mistake in the build and it was literally the last thing...racing to the finish line). Same question about the bias though.

 

[Homestudio]

Troubleshooting question:

Is the ground pin and heater pin supposed to be tided together? I have continuity between the two on the microphone’s 7 pin connector.



I need help with my mic build. I come from a music background not an electronics background. Love to learn new things ( already good with soldering iron, fair with multimeter, not very good with schematics) and took on this project to do just that. Build is complete with less expensive components (capsule &tube). Have calibrated B+ and heater to spec on psu. Plugged mic in. B+ on mic is good. Tube heats and lite glow. No signal from mic. No hiss, nada. So now I get to learn to troubleshoot! I’ve been reading the mic troubleshooting thread but again I’m not good at reading and understanding schematics. So I started at the mic thinking the psu is ok. Checked that head basket and bottom of body have continuity, assuming this means they’re grounded. That’s good. Checked 7 pin connecter. Now here is my first question in my trouble shooting quest. Please see above. Any other advise is greatly appreciated. Much thanks.