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

[Pip]

Finished build:

CT12 capsule

AMI T14 transformer

Standard component compliment no alterations.

Sounds great works great love this a lot more than my C12 clone.

Had one hiccup. When I first powered up the mic and set all voltages with mic in Omni all voltages set right out of the box and all sounded great. Switch to Cardioid and output of front capsule dropped off the charts switched to Figure of 8 and all worked but front capsule lost highs?! Started doing the visual and then meter check and all seemed OK. But no change when tapping around?!. Started to get depressed about it as I really took my time with the high impedance part of this mic and, if I do say so myself, my work was tight on this one. So after deciding I needed to either rip apart the high impedance stage and start over or maybe it was the relay contacts I had that moment of well maybe, as almost impossible as it might be, there was something wrong with Tim Campbell's capsule.

So I pulled off the headbasket and went about seeing if the backplates were isolated, there where no shorts, no cold solder joints and nothing touching that shouldn't etc... All checked out! That's when it hit me. Tim Campbell ships his capsules with all the screws and solder tabs attached so I just followed this. The backplate tab connections while isolated are shipped right next to each other but yet he offers alternate spots on the capsule "for convenience". Well I have had problems in the past with proximity of connections causing problems in the high impedance circuits of mics, just not enough air between them. So I moved one of the backplate tabs to one of the alternate connection points. Bobs your Uncle all is right with the world the mic and Tim's Capsule are as one with the audio universe! Mic is working like a charm and really sounds like I dreamed it would.

This one is worth the time and effort!!!!

 

[Pip]

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

Hi Dan, Thanks for your interest!

I have made a few more changes to the mic now. I posted these changes in another response but I will paste them here as well..
It turns out I made a mistake about that tantalum replacement 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. 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 bit more bottom, not as pronounced as the Silmic but still worth it. I also changed out the 100uf filter cap and put in a 330uf. This one I did not notice so much. One other cap that I have put in is again on the stores recommendation was a Solen MKP-FC 3.3UF 400V. That one for me did not show much change  from the original one that I had. I have made audio clips, and uploaded them into a small zipped pro tools session. These are really terrible recordings!  The guitar I have is a real good looker, but man it sounds terrible. Its an old F hole Kay from the 50s that I got for $20, its all I got here in Taiwan. So mainly I just did a guitar to show the differences between part swaps. I tried my best to be in the same location, but still it sounds pretty different before and after the capsule voltage change. I still want to do more testing but I think its a good bit better that it was when I started. I do hear a bit of noise on the mic now though it seems, but not sure its not just the environment here. Seems like the original test I did next to the new telefunken 251 was quieter, but it was across the street in an actual vocal booth instead of my control room which has a console fan running! I think it might be time for capsule and transformer changes next. Anyone have any thoughts of what might be a good choice, please let me know! Thanks

https://www.dropbox.com/s/ilyhotu9tdet6i7/Copy%20of%20251%20mic%20test%202.zip?dl=0
[/quote]

Noise creeping in after the fact speaks more to tube then anything else IMO! Transformer depends on capsule but I like the AMI. Tim Campbells capsule for my money is the best and he stands behind his product. If you are looking for a warmer voiced capsule then the C12 standard check out Beesneez for both of these capsules I recommend AMI.

 

[micaddict]

Hey Pip, coincidentally, when  I was reading through some of the  classic threads today, I saw your first post.
It was posted on April 9th 2013, in the C12 thread. And I happened to be the first to welcome you there.
Time flies, but you've done well! Keep at it. 

And now a 251 finished. 

Sounds great works great love this a lot more than my C12 clone.

Could you please elaborate why?



Henk

 

[Pip]

Hey Pip, coincidentally, when  I was reading through some of the  classic threads today, I saw your first post.
It was posted on April 9th 2013, in the C12 thread. And I happened to be the first to welcome you there.
Time flies, but you've done well! Keep at it. 

And now a 251 finished. 

Sounds great works great love this a lot more than my C12 clone.

Could you please elaborate why?



Henk

Firstly Thank You!


To my ears it has a more even timbre it is not as bright as the C12 and yet retains a very good top it also is rich and warm sounding. It is less susceptible to sibilance issues. They both have CT12 capsules. I just think this mic to me sounds like I would put it up and not fuss with it as much with EQ. It sounds like an Ela M 251 which I have always personally preferred over the venerable C12.

 

[micaddict]

Thanks. 

 

[Matt55]

Actually there is no standard for 7 pin wiring  so you can actually make your own scheme if you will
just make sure it follows the logic from the psu to the mic pcb and you will be fine ,
I just have an habit of following the Neumann scheme for my cable ,  I have wired my cable like this ,
but since this one have 2 pattern control it deviates a little bit from it , but as said if you are using a Gotham cable
reserve the blue wire for Circuit ground and the red wire for the heater as those are the biggest gauge to handle more current
as said you can define your own cable configuration from psu to mic as long as it is following the logic.

here is an example :

1-audio +
2-audio -
3- (Relay control 1) to OMN
cable shield  = up to xlr tab as well
4-heater
5 B+
6 Pattern control ( relay control 2  ) to Fig 8 on mic pcb ,
7 circuit ground

Couple of questions;

When you say cable shield  = up to xlr tab as well what do you mean exactly, not sure I fully understand?

Is there a preference to the length of cable from the mic to the PSU. Is shorter better or no preference?

Thanks for the Help.

Regards,

  Matt

 

[ding]

I think he means the cable shield is soldered to the XRL tab. Some XRLs come with 1, 2, 3 and tab.

 

[Matt55]

Yeah thats exactly what he means! I had a blonde moment and though he was refering to something else!

Any notes/thoughts regarding the 7pin XLR cable length? Basically i have two options, place it under the desk or at the base of the mic stand.

One cable would be approx 2-3m the other would be 6-8m?

Thanks, Matt

 

[Rlucas41]

Hi Dan and fellow DIY folks,

I am completing another build (ElaM-251) the mic sounds great, getting good voltage reading 6.3vdc on H+, and exactly 120vdc on B+

Cardioid is great, Omni is great, but not getting anything when I switch to figure 8… getting continuity from switch to f8 pad on mic pcb, and I think my wiring is correct… Any suggestions?

I think I may have an issue with backplate separation as I am getting continuity between the FB and RB pads with the leads connected.

 

[bbernd]

Hi Guys,

at the moment I'm building my first M251 and I'm really looking foward to listen to the result.

Hopefully you can answer me one question: According to the M251 Building Guide I have to use a GND hole on the PSU PCB to ground the signal (marked yellow on attached picture).
Because of my PSU layout, it would be easier to reached the GND Slot on the Terminal Block (marked red on attached picture). Is it possible to use this point instead of the place, which is recommended in the M251 Build Guide?

Thank a lot for your answer.

Bernd

 

[ding]

I took a look at the schematics cause I'm trying to find out which triode this PCB uses. It looks like the original 251 schematic shows the second triode being used but the D251 is using the first triode. Is this correct?

 

[Pip]

It doesn't matter but yes!

 

[ding]

Well when you are selecting a tube with only one mic grade triode it's good to know which triode you will be using.

 

[Pip]

Well when you are selecting a tube with only one mic grade triode it's good to know which triode you will be using.

One of the nice things about these 6072/12AY7 based mics is that if one side goes bad its not that hard to rewire to use the other side. IMO if you are selecting tubes or buying selected tubes they are usually best tested in the mic they are going to be used in with the voltages set for the tube in question burned in for a good few days and listened to critically with head phones.

I have found recently after going through several dozen tubes in this manner that while quite good sounding the GE 5 Star tubes I have were not as quiet as the GE JAN tubes. In general these NOS mic grade tubes are getting harder and harder to find. I have recently started looking at New Stock alternatives.

 

[Tim Campbell]

Rlucas41
Is there continuity between the backplates without any wires connected to them? Then you have shorted backplates.
With the wires connected it could be the circuit.
Who's capsule is it? Please contact the manufacturer to find out about returning it so that it can be cleaned or lapped.

 

[bbernd]

Hello,

just finished my M251 Build and I'm really happy with the result. At least the cardioid pattern is awesome! 
Thanks to all the advises and help in this thread!

I recorded an audio sample with the different pattern. If you want, feel free to listen to the files.
There you can also hear a comparison to a Microtech Gefell MT71s.


https://www.dropbox.com/sh/bx4fk73njzxlg8t/AAD9ZV42sdgfS9zQ1f3AKYtsa?dl=0


Unfortunately I guess there is something wrong with the omni and the figure 8 pattern. The  omni is boosting the high-mids and the top end - the figure 8 cuts it. Voltage of B+ is 110V and H+ 6.3 V. I used a vintage microphone CEK12P capsule. I already tried to find a short between the backplates but didn't found any problem. Any other ideas?

Thanks a lot.

Bernd

 

[micaddict]

The  omni is boosting the high-mids and the top end - the figure 8 cuts it.

If it's subtle (!), it's "normal". 
For the top end that is.
The mids tend to shift a bit when changing patterns.
Lows are deepest in omni and most rolled-off in fgure eight. But the latter has maximum proximity effect.

Then again:
http://recordinghacks.com/microphones/Telefunken-USA/ElaM-251E

Hmmm ......
I wonder how representative those plots are. As a rule omni is the brightest and figure eight the darkest.

 

[Delta Sigma]

Finished a build with a Beesneez body and capsule. This thing sounds great. I fired it up with an EH 12AY7, replaced that with my 1953 five star from Bowie, then replaced the Polypropelene film cap with a wet tantalum. Not sure I could tell much difference between the two caps but I have a sinus cold and my ears are a little out of sorts.

The Beesneez body is beautiful and fits the board perfectly. I hope there's more projects in the future that the Sneesbys will customize a body for. It ended up being a steal of a deal with the package including the Beesneez CK12.

 

[Delta Sigma]

Gutshot.

I did notice that this thing is louder in cardiod than omni and figure 8. I remember someone mentioning that so i'm assuming it's normal for the circuit.

 

[micaddict]

You've got a quality mic there in every sense of the word.