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

[trans4funks1]

Hi Dan,
I am looking forward to receiving the PCB kit I ordered over the weekend. Thanks for making it available. I'm ordering the BOMs from Mouser this morning.

Do you plan to make a specific schematic available that represents your changes to the AKG schematic you posted above?

I anticipate difficulty in understanding how those relays are set up and while I know I can simply follow your photos as step by step instructions I will enjoy learning what is actually going on inside the yellow boxes.

I appreciated being able to view your PSU schematic for the 269 project, and since I am actually going to attempt build/mod a "Walter White" I'd like to have the same opportunity to study the design you used for this PSU PCB.

I'd appreciate any info you can share, even if it is just some sort of hand drawn schematic detail of how the relays fit in to the official AKG switch detail you posted.

Thank You!

 

[toobnoob]

Sweet Googly Moogly that looks awesome!

 

[RuudNL]

Why build an ELA M251 clone if you have two of them in your microphone locker?

 

[poctop]

Why build an ELA M251 clone if you have two of them in your microphone locker?

Then you obviously dont  , if you are lucky enough to have them already Then Enjoy,
D

 

[trans4funks1]

There may be some guys that bought their first two for $300 and don't want to spend an extra $10,000 on a third one.

 

[poctop]

Do you plan to make a specific schematic available that represents your changes to the AKG schematic you posted above?

I anticipate difficulty in understanding how those relays are set up and while I know I can simply follow your photos as step by step instructions I will enjoy learning what is actually going on inside the yellow boxes.

I appreciated being able to view your PSU schematic for the 269 project, and since I am actually going to attempt build/mod a "Walter White" I'd like to have the same opportunity to study the design you used for this PSU PCB.

I'd appreciate any info you can share, even if it is just some sort of hand drawn schematic detail of how the relays fit in to the official AKG switch detail you posted.

Dont worry i will adress your request  soon enough.



only 1 set left,
PM for details if interested ,

in the eventuality that i could make another run of those , please post on this thread if i have enough folks i will proceed to round 2
i am just selling my leftover for now hence the number of set is very limited,


Best,
Dan,

 

[toobnoob]

Next time you do a batch I'd be down for 2 8)

 

[Woot]

I anticipate difficulty in understanding how those relays are set up and while I know I can simply follow your photos as step by step instructions I will enjoy learning what is actually going on inside the yellow boxes.

I'm also not too sure exactly how these are implemented.

From the ELAM schematic the switching pattern is a 3P3T configuration.

So the 3 x DPDT relays are taking over the function of the 3P3T switch.

Now to sit down with a bit of paper and figure out how...

 

[Winetree]

Going to wait for Chunger new mic shipment.
I'm in for 2  sets in round 2.

 

[poctop]

still 1 left ,
Let me know

 

[poctop]

still 1 left ,
Let me know

Gone ,
thanks ,
Dan,
Stock out,
Best,

 

[kcguitar]

I'm in for 2 sets for round 2.  Any estimate when they will be available? 

 

[Dylan W]

In for a pair on round 2.

 

[trans4funks1]

Hi Dan,
What are the 2 diodes labeled D1 and D2 for?

Will the AMI T-14 fit just as well as the Cinemag in the transformer slot?

Thanks.

 

[vineyardgray]

Count me in for a pair for round 2. 

 

[Woot]

What are the 2 diodes labeled D1 and D2 for?

The mouser BOM suggests they are relay voltage suppression diodes.

I found this simple relay info:

http://www.autoshop101.com/forms/hweb2.pdf

Page 11/12

 

[Woot]

So I had a bit of a sketch re the relay switching and this is what I came up with.

The relays are drawn as individual DPDT switches, with the coil connectors not shown.

The connections from the capsule to the main circuit are labelled A, B and C from top to bottom.

As shown in the previous relay schematic, in the de-energised state there is a connection between the poles and the middle pins. In the energised state there is a connection between the poles and the upper pins.

The switch on the PSU would then need to only supply 2 rails of coil voltage for figure of 8 and omni, with the PSU position for cardioid being no connection.

Am I close?

 

[trans4funks1]

Hi Woot,
Thanks for explaining about the diodes. Now I'm scratching my head wondering why there aren't 3.

Thanks for making a sketch of the relay network. I'll give it a look. I spent last evening studying some drawings and photos of similar set  ups on another thread here and I was left thinking I could wire it up but not really understand it. You provided some extra details about the routing that are helpful.

I am very curious to see the PCB and get this figured out. I have my self made drawing of the traditional 251 and I have cleared out the switch and added the relay schematic symbols in anticipation of getting this figured out.

 

[poctop]

So I had a bit of a sketch re the relay switching and this is what I came up with.

The relays are drawn as individual DPDT switches, with the coil connectors not shown.

The connections from the capsule to the main circuit are labelled A, B and C from top to bottom.

As shown in the previous relay schematic, in the de-energised state there is a connection between the poles and the middle pins. In the energised state there is a connection between the poles and the upper pins.

The switch on the PSU would then need to only supply 2 rails of coil voltage for figure of 8 and omni, with the PSU position for cardioid being no connection.

Am I close?

I am Travelling this week so it quite tough to validate this one without my Master Schematic, but from the top of my head this is it ,
it needs indeed 2 different supply control voltage for the different combination and 2 optional supressing diode, as a pair of relay are activated simultaneously for all the patter to work, the tricky part was to ellaborate a way of having this floating from the board and still be solid and have enough room to supply those 2 control lines from the small area the pcb. the mic is super silent too I can confirm that. you really did your homework on this and i bet you had fun doing it.
I did  ,
Best,
Dan,

 

[poctop]

Hi Dan,
What are the 2 diodes labeled D1 and D2 for?

Will the AMI T-14 fit just as well as the Cinemag in the transformer slot?

Thanks.

Supressing diode indeed,  yes the aMI T14 will fit nicely there,
Best,
DAN,