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

[ding]

Where are people getting these elusive 3.2uf 450v wet tantalums that I can't seem to find anywhere? I've been looking for days on the interwebs.

 

[Delta Sigma]

I think someone mentioned using these guys:
http://www.ebay.com/itm/2-Sprague-109D365X0125C2-3-6uF-125V-20-Wet-Tantalum-Capacitors-/191130283180

Mouser has brand new wet tants but they're in the $70 ea range.

 

[iprovlek]

Real Haufe T14/1 is  1:11,5 ratio!

And here is schematics of Elam250!

And 1uF is for output capacitor!

 

[iprovlek]

So instaed 3.2uF tantalum you can put 1uF film capacitor, 2.2uF or even 3.3uF to get more low end!

 

[Delta Sigma]

Where can I buy AMI transformers?

Can they still be purchased through [email protected]?

 

[Matt55]

I was also looking at the Sprauge 109D's at the ebay link here for my 251. Waiting for a reply from the seller as im in the UK.

http://www.ebay.com/itm/2-Sprague-109D365X0125C2-3-6uF-125V-20-Wet-Tantalum-Capacitors-/191130283180

I believe JessJackson used these as explained on page 9 of the thread and it gave the mic the more 3D sound of the original which was why I was interested, he definitely preferred them... There are sound files you can download and compare.

I found a few options  however they seem to be either longer than 51mm or to wide to fit in the body. Other builders have left notes saying its vital to get a good coupling cap but then dont leave details about which one they preferred...

It would be really appreciated if people could provide acutal link of one they used and why it made it better/worse/different! I am working on my build next week so im pretty excited

Thanks, Matt

 

[Matt55]

I got my T14 from AMI by contacting them direct. Replied same day! Hope that helps.

 

[ding]

I think someone mentioned using these guys:
http://www.ebay.com/itm/2-Sprague-109D365X0125C2-3-6uF-125V-20-Wet-Tantalum-Capacitors-/191130283180

Mouser has brand new wet tants but they're in the $70 ea range.

These are 125v. I don't think they will stand up to the task. Who ever is using these I would be very careful cause the voltage could really damage the cap.

 

[Delta Sigma]

These are 125v. I don't think they will stand up to the task. Who ever is using these I would be very careful cause the voltage could really damage the cap.

David Bock discussed this earlier in the thread.

I've never seen the wet tant in a 251 short out (I have seen loss of capacitance), though I've seen plenty of tants short out in ATR124 decks taking down the whole machine (smoke optional).
I have also seen original T14/1 xfmrs go open. That wire is mighty fine.
IF your new build mic does not copy the exact footprint of the 251, you should have more room for other cap options. Then you can listen and decide for yourself. But in a vintage 251, space is at a premium so the original cap is a must, unless you are willing to crack the plexiglass body, as some repairs guys are willing to do. FYI there is no electrolytic that will fit in that space that sounds good so don't bother.
Yes you can use a 125v cap, though it's safer with higher tolerances. The occasion of reaching 125v across the cap occurs at power up, when the B+ is there but the tube hasn't fully heated. Reaching full B+ once the tube is heated will likely not happen during normal use, unless you stick it in a kick drum.
I have found NOS went tants (of the value you need for this mic), even recently, so I know they are out there

You're definitely right, higher voltage ratings would be ideal. The problem I see is without having compared wet tantalums to either film type, I don't know what I'm going to prefer. To even buy a 3uF wet tant from mouser rated at 150V you're sinking $100 CAD ($70 for 125V).  I figure $20 for the NOS 125V 3.6uF wet tantalums from Ebay is worth trying and I'll probably get good life out of it. Maybe, I could even delay or switch the B+ and get even more life out of it.

Does anyone know another source for the Polyester film cap? It's no longer stocked at Mouser and there's no others available in singles.

 

[midwayfair]

Finished up a build that was mostly completed by Christopher L. Did a teensy bit of parts stuffing and troubleshooting in the PSU (goo learning opportunity) on the heater supply and picked up the body and PSU from Studio939.

Sounds amazing, and it's exactly what I was looking for: Slightly brighter than a u47 and slightly darker than a C12 (EDIT: apparently the newer C12s are actually more different than I thought, so I guess a regular C12 build would have sounded almost identical to this). The noise floor is super low.

I really like the relay switching. Very cool.

I'm ready to conquer my next mic from scratch I hope

 

[andybaker28]

Hi again,

I am having trouble figuring out how to lower my capsule voltage to 55V. I have tried looking at the schematic but just able to know for sure what I am doing! I have read that I need to change a resistor on the voltage divider, but I am not able to understand..

Thanks for any help

Andy

 

[midwayfair]

Hi again,

I am having trouble figuring out how to lower my capsule voltage to 55V. I have tried looking at the schematic but just able to know for sure what I am doing! I have read that I need to change a resistor on the voltage divider, but I am not able to understand..

Thanks for any help

Andy

You're looking for two high-value resistors that cut the voltage in half as a reference voltage before a VERY VERY high value resistor that provides the charging voltage for the capsule on the capsule's side of the input capacitor.  Trace backward through the schematic from the capsule connection and you should find these. Hopefully that's enough of a hint. (There aren't many components in the mic itself.)

Right now the two high-value resistors take a B+ of 120V and make it 60V. If you aren't sure what value to use for the voltage divider, here's a calculator: http://www.raltron.com/cust/tools/voltage_divider.asp

 

[andybaker28]

Hi again,

I am having trouble figuring out how to lower my capsule voltage to 55V. I have tried looking at the schematic but just able to know for sure what I am doing! I have read that I need to change a resistor on the voltage divider, but I am not able to understand..

Thanks for any help

Andy

You're looking for two high-value resistors that cut the voltage in half as a reference voltage before a VERY VERY high value resistor that provides the charging voltage for the capsule on the capsule's side of the input capacitor.  Trace backward through the schematic from the capsule connection and you should find these. Hopefully that's enough of a hint. (There aren't many components in the mic itself.)

Right now the two high-value resistors take a B+ of 120V and make it 60V. If you aren't sure what value to use for the voltage divider, here's a calculator: http://www.raltron.com/cust/tools/voltage_divider.asp

Hi there and thanks so much. I tried to follow what you said. I am trying to learn! I am thinking that maybe I could try putting a 13K ohm resistor in place of R5, and a 15K R3? Would that do what I need? I do appreciate it very much!

Andy

 

[midwayfair]

Hi again,

I am having trouble figuring out how to lower my capsule voltage to 55V. I have tried looking at the schematic but just able to know for sure what I am doing! I have read that I need to change a resistor on the voltage divider, but I am not able to understand..

Thanks for any help

Andy

You're looking for two high-value resistors that cut the voltage in half as a reference voltage before a VERY VERY high value resistor that provides the charging voltage for the capsule on the capsule's side of the input capacitor.  Trace backward through the schematic from the capsule connection and you should find these. Hopefully that's enough of a hint. (There aren't many components in the mic itself.)

Right now the two high-value resistors take a B+ of 120V and make it 60V. If you aren't sure what value to use for the voltage divider, here's a calculator: http://www.raltron.com/cust/tools/voltage_divider.asp

Hi there and thanks so much. I tried to follow what you said. I am trying to learn! I am thinking that maybe I could try putting a 13K ohm resistor in place of R5, and a 15K R3? Would that do what I need? I do appreciate it very much!

Andy

Those resistors are presently 500K. 15K and 13K are orders of magnitude smaller. I suppose you could go do some calculations to find out what the demands on the power supply and components would be if you used resistors that small, but I think it's fair to tell you that you should stick to values closer to what's already in the microphone.

EDIT: You can do it with two standard (easy-to-find) values, as well.

 

[andybaker28]

Hi again,

I am having trouble figuring out how to lower my capsule voltage to 55V. I have tried looking at the schematic but just able to know for sure what I am doing! I have read that I need to change a resistor on the voltage divider, but I am not able to understand..

Thanks for any help

Andy

You're looking for two high-value resistors that cut the voltage in half as a reference voltage before a VERY VERY high value resistor that provides the charging voltage for the capsule on the capsule's side of the input capacitor.  Trace backward through the schematic from the capsule connection and you should find these. Hopefully that's enough of a hint. (There aren't many components in the mic itself.)

Right now the two high-value resistors take a B+ of 120V and make it 60V. If you aren't sure what value to use for the voltage divider, here's a calculator: http://www.raltron.com/cust/tools/voltage_divider.asp

Hi there and thanks so much. I tried to follow what you said. I am trying to learn! I am thinking that maybe I could try putting a 13K ohm resistor in place of R5, and a 15K R3? Would that do what I need? I do appreciate it very much!

Andy

Those resistors are presently 500K. 15K and 13K are orders of magnitude smaller. I suppose you could go do some calculations to find out what the demands on the power supply and components would be if you used resistors that small, but I think it's fair to tell you that you should stick to values closer to what's already in the microphone.

EDIT: You can do it with two standard (easy-to-find) values, as well.

Hi and thank you again! I had another look and have attempted again at some common value resistors closer to original. I am a bit confused on how the relationship between the two resistors values work. In the calculator it mentions R1 and R2, if the values of these two are reversed it has a change on the output voltage. In the microphone schematic it appears to my pea brain that on the 251 diagram  R3 would act as R1 on the calculator, and R5  would act as R2 on the calculator. I wonder if that is correct. I do appreciate your help. I am thinking now then that possibly R3 should be a 560K and R5 should be a 470K. This would make my voltage 54.7, I think…

Andy

 

[ding]

Hi and thank you again! I had another look and have attempted again at some common value resistors closer to original. I am a bit confused on how the relationship between the two resistors values work. In the calculator it mentions R1 and R2, if the values of these two are reversed it has a change on the output voltage. In the microphone schematic it appears to my pea brain that on the 251 diagram  R3 would act as R1 on the calculator, and R5  would act as R2 on the calculator. I wonder if that is correct. I do appreciate your help. I am thinking now then that possibly R3 should be a 560K and R5 should be a 470K. This would make my voltage 54.7, I think…

Andy

Hey Andy, did you get that going? How does it sound?

 

[andybaker28]

Hi and thank you again! I had another look and have attempted again at some common value resistors closer to original. I am a bit confused on how the relationship between the two resistors values work. In the calculator it mentions R1 and R2, if the values of these two are reversed it has a change on the output voltage. In the microphone schematic it appears to my pea brain that on the 251 diagram  R3 would act as R1 on the calculator, and R5  would act as R2 on the calculator. I wonder if that is correct. I do appreciate your help. I am thinking now then that possibly R3 should be a 560K and R5 should be a 470K. This would make my voltage 54.7, I think…

Andy

Hey Andy, did you get that going? How does it sound?

Hi there, I actually did buy the resistors but not yet installed them, in the meantime though I did switch the .22 uf Tantalum to a 100uf Tantalum and did not hear a change. Then later switched the 100uf Tantalum to a 100uf gold panasonic electrolytic and man the bottom really came up then. I did not have much time to test it on acoustic guitar yet, but the low on my vocal was much more without being muddy or too much. I will try the resistor change to lower the voltage down to 55V soon, I was sort of wanting to see if what I had calculated was correct first. I guess it won't damage  anything to try! I will keep you posted as I proceed!
Thanks again

Andy

Andy

 

[poctop]

Hi and thank you again! I had another look and have attempted again at some common value resistors closer to original. I am a bit confused on how the relationship between the two resistors values work. In the calculator it mentions R1 and R2, if the values of these two are reversed it has a change on the output voltage. In the microphone schematic it appears to my pea brain that on the 251 diagram  R3 would act as R1 on the calculator, and R5  would act as R2 on the calculator. I wonder if that is correct. I do appreciate your help. I am thinking now then that possibly R3 should be a 560K and R5 should be a 470K. This would make my voltage 54.7, I think…

Andy

Hey Andy, did you get that going? How does it sound?

Hi there, I actually did buy the resistors but not yet installed them, in the meantime though I did switch the .22 uf Tantalum to a 100uf Tantalum and did not hear a change. Then later switched the 100uf Tantalum to a 100uf gold panasonic electrolytic and man the bottom really came up then. I did not have much time to test it on acoustic guitar yet, but the low on my vocal was much more without being muddy or too much. I will try the resistor change to lower the voltage down to 55V soon, I was sort of wanting to see if what I had calculated was correct first. I guess it won't damage  anything to try! I will keep you posted as I proceed!
Thanks again

Andy

Andy

Thanks Andy
for your tweak experiment results ,
I have made a list now on Page 1 of this thread
http://groupdiy.com/index.php?topic=55010.0

so I will try to compile those tweaks as they go and be interesting
Best,
Dan,

 

[JessJackson]

is it a wet tant andy

 

[andybaker28]

is it a wet tant andy

Hi there, Well it turns out I made a mistake about that cap! I had gotten it from a hifi shop here in Taipei on the store owners recommendation. When I saw it I thought immediately that it was a Panasonic Gold and thought nothing more of it! But today on further examination I realised I was wrong! Sorry for that! It is actually an Elna Silmic ARS. Exactly like this one listed on ebay in the link below. This made a very nice change to the low end of the mic, I can definitely suggest this as one to try! I don't plan to look further than this one for now. It really makes the original recording test I did sound very thin. I have also swapped out a 600K into R3, and a 510K into R5 replacing the original 500Ks  that were in there. That also seemed to add a tiny bit of low to it, not as pronounced as the Silmic. One other cap that I have put in is again on the stores recommendation was a Solen MKP-FC 3.3UF 400V. Also shown below in an ebay link. That one for me did not show much change  from the original one that I had. I have made audio clips, but I doubt they are of much help. I will upload them into a file soon!

http://www.ebay.com/itm/ELNA-SILMIC-ARS-Capacitors-100u-16v-2pcs-/321219958541

http://www.ebay.com/itm/1-pc-Solen-MKP-FC-Capacitor-3-3uf-400v-France-brand-new-/271119840331?hash=item3f2000744b