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

[micaddict]

I've started a separate, feeler thread concerning a Beesneez body, taylored for this project.

http://groupdiy.com/index.php?topic=55176.0



Henk

 

[bockaudio]

The TE-1501 appears to be aluminum cap, not wet tant. It's for the coupling cap. It does indeed look like the caps Telefunken USA uses quite a bit in their reissues.

I really do urge you to either find the wet tant or make space for PIO.
IIR I have consistently found WT's at assorted Surplus places.

 

[trans4funks1]

Hi David,
Thank you for expressing this with emphasis.

I have been looking around online for Wet tantalum and Paper in Oil caps in the 125vDC to 450vDC range and can only find limited selections.

It seems like if you are willing to find them you can find them.

I have a question regarding the capacitance value. I recall seeing discussion regarding opinions about values other than 3.2uf but I am having trouble finding reference to the discussion in my notes.

I am wondering, since it is not particularly easy, or affordable, to locate an assorted supply of Wet Tantalum capacitors, if you or someone can offer a general overview of the implications of using values different than 3.2uf.


Thank you.
 

 

[bockaudio]

I have a question regarding the capacitance value. I recall seeing discussion regarding opinions about values other than 3.2uf but I am having trouble finding reference to the discussion in my notes.

You could increase the grid resistor and reduce the output cap value. Go up to 250M and down to 1uF.

 

[OPR]

+1

250M and down to 1uF.

particularly if your using a Chinese Ck12 capsule as they don't have the LF response of the real capsule or an accurate clone.

 

[trans4funks1]

Well done Dan in taking over the project... It was too much for me to get done with everything else going on at the moment.

I do think maybe take a look at our last design (version 6.5) as this was the closest i feel to perfection in utilizing the relays.


The cathode bypass components would be floating on back of tube base hence displayed off of the board.

Hi Jess,
I took a look at the board you posted an example of to learn how you planned to use the relays and I can not figure out how it can work. I drew a schematic, as I did with Dany's layout, and I am hoping I am missing something you can explain. I can't unlock the puzzle of how the board you posted a image of provides all 3 patterns.

Any clues?

Thank You.

 

[poctop]

Well done Dan in taking over the project... It was too much for me to get done with everything else going on at the moment.

I do think maybe take a look at our last design (version 6.5) as this was the closest i feel to perfection in utilizing the relays.


The cathode bypass components would be floating on back of tube base hence displayed off of the board.

Hi Jess,
I took a look at the board you posted an example of to learn how you planned to use the relays and I can not figure out how it can work. I drew a schematic, as I did with Dany's layout, and I am hoping I am missing something you can explain. I can't unlock the puzzle of how the board you posted a image of provides all 3 patterns.

Any clues?

Thank You.

did you get the schematic I posted ?
Best,
dD

 

[trans4funks1]

Hi Dany,
Yes I downloaded it right after you posted it. It was very helpful. Thank for posting it. I had thanked you and I sent you that message about C3 too.

I am interested in the idea that there may be several relay switching solutions to achieve the same goal and I enjoy the exercise of thinking it through.

Thank You.

 

[poctop]

Hi Dany,
Yes I downloaded it right after you posted it. It was very helpful. Thank for posting it. I had thanked you and I sent you that message about C3 too.

I am interested in the idea that there may be several relay switching solutions to achieve the same goal and I enjoy the exercise of thinking it through.

Thank You.

Yes Thanks again for catching C3  , Very helpfull too ,
I was just curious to see if you were refering to Jesse Board saying that i could not work out so was  just checkin if you had found another mistake in the pattern switching on mine  I really checked that part a million time and with the built mic  ;D
I am all ear if you can find an easier way.
Best,
dD

 

[trans4funks1]

Hi Dany,
I learned a lot by working through your example. I think you nailed it.

 

[Woot]

Hi DAn,

Received the boards with thanks. They are great! So it is with apologies that I present this.... This is the standard ELAM 251 body from BeezNees.

Lots of curiosity, much impatience and some precision dremeling

The only thing I can see is that the copper ground layer is exposed on the left and will therefore short to the mic body. Is this OK, or ideally should it be isolated?

Or if this is really a bad idea, then please let me know and I'll leave the other one alone.

Thanks,

Matt

 

[Woot]

Just needs a tidy up filing...

For anyone wondering that's approximately 10mm up the board.

 

[Winetree]

Woot, Thanks for the pix.
Are you using the same body that's listed in this FEELER?

http://groupdiy.com/index.php?topic=55176.0

I've got the same board and am considering this Beeneez body.

 

[micaddict]

The body in the feeler (if we get enough takers) will be an exact fit. This means it will be longer if necessary, it will have corresponding holes in the rails etc.



Henk

 

[micaddict]

BTW, do we need an opening for a pattern switch?

 

[Woot]

I did this with the original size body from BeesNeez, the bodies in the feeler don't exist yet

I haven't confirmed that the AMI T14 or any other trafo will fit snugly down in that recess with the XLR but I can't see it being an issue just from eyeballing it. When I do the install, I'll update everyone accordingly.

I can see the benefit from having a custom made body, but given that Veronica said there would be an MQ, and the usual time it takes to get these things rolling, I just thought I'd do a simple hack job, to see whether it could work if the other plan fell through.

8)

The other problem I foresee is that it won't matter where you drill the holes as the board in current dimensions doesn't over lap the struts. Make it wider, then it'll be too fat for the Alcatron et al mic bodies.

 

[micaddict]

The other problem I foresee is that it won't matter where you drill the holes as the board in current dimensions doesn't over lap the struts. Make it wider, then it'll be too fat for the Alcatron et al mic bodies.

Yeah, I've thought about that one. Well, in any case the collaboration will result in the best, practical solutions I'm sure.
Hey, removable ears on the PCB maybe?  :

So, what do you guys think would be the best place to discuss these details; this thread or the feeler?
I would think the latter, but I'm not sure.


Henk

 

[poctop]

The only thing I can see is that the copper ground layer is exposed on the left and will therefore short to the mic body. Is this OK, or ideally should it be isolated?

Or if this is really a bad idea

the ground plane is actually made to make contact with the mic body , but the intended purpose is trough the mounting hole on the side tough ,
the upper parts where the relay sits is the critical place because there are the relays pads there and some component pad those should be clear rfom the mic railing at all times,  bythe look of it i think it will fit nice.

Hope this helps,
BEst
dD

 

[kcguitar]

After building 2 fantastic Tim Campbell equipped sounding ELAM's this past weekend, I just wanted to mention that with the HT-11A bodies, the relays are a VERY tight fit and the 2 outside ones will rub against the body tube.  I was somewhat able to alleviate this by angling the 2 outside relays in so that their outside corners sat a little closer towards the center K2 relay.  Also I cut the leads for C4, R6, and R4 short enough that they did not protrude through the board so that they relay wouldn't have to sit any farther out than it needed.  Finally I was able to carefully file the corners of the relay in at a 45 degree angle.  My boards still flex just a bit when assembling the mic from the relays hitting the body tube though  :-\

Anyways hope that helps with anybody that has yet to use these boards in conjunction with the HT-11A's.   

 

[Melodeath00]

The other problem I foresee is that it won't matter where you drill the holes as the board in current dimensions doesn't over lap the struts. Make it wider, then it'll be too fat for the Alcatron et al mic bodies.

So how do you plan to attach the PCB?

BTW, do we need an opening for a pattern switch?

Room for a pattern switch would be great. However (and I could be very wrong), I thought I read somewhere that the proper switches do not exist anymore. Again, I could be way off base here.