S52 - Small Diaphragm Condenser Tube Microphone (5840, NT10/3)

[ln76d]

Starting new project!
(still have many other unfinished but i couldn't resist )

This time SDC Tube microphone!
I'll be making a pair.
Circuit can be used with many different donor microphones like mxl, apex, alctron, sontronics, joemeek, oktava as also many others! Everything which fit whole circuit. Tube and transformer are really small, so there shouldn't be a problem with most of donor microphones. Except the tube it has nothing to do with Royer circuit

Tube - EF732 / 5840

Transformer - Neutrik NTE10/3 (wired backward for 10:1 ratio)

Resistors:

R1 - 10M
R2 - 1G
R3 - 1G
R4 - 1M
R5 - 1M
R6 - 100K
R7 - 3.3k

Capacitors:

C1 - 22nF
C2 - 470pF
C3 - 10uF (bipolar)
C4 - 10uF (bipolar)
C5 - 470nF
CX - from 100pF to 470pF for overbrighted capsules

PSU - could be this one:
https://www.thomann.de/pl/the_tbone_psu_sct_700.htm?ref=search_rslt_psu+t.bone_109920_0
I will check if it will run two microphones

Some values can change after tests!

Polarisation voltage is set to 50V

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All microphones projects:
https://groupdiy.com/index.php?topic=62423.0
https://groupdiy.com/index.php?topic=62441.0
https://groupdiy.com/index.php?topic=64687.0
https://groupdiy.com/index.php?topic=62601.0
https://groupdiy.com/index.php?topic=63436.0
https://groupdiy.com/index.php?topic=63682.0
https://groupdiy.com/index.php?topic=62262.0
https://groupdiy.com/index.php?topic=62682.0

 

[lampas]

No one interested in that ? Then I'll ask the first question ... How does it sound ?

 

[ln76d]

Hey Vili!
Thanks for interest

Probably you are the only one
To get any attention i will  have to call it u47, c12, M251 etc.
Make full kit, even with stripped wires, ugly color PCB - orange would be original
Find chinese aluminium body for it and sold for twice than it's worth
Ahh!!! Also transformer will have to be ami or cinemag
Maybe then someone will be interested!

Ok, now about the microphone!
Still don't know how it sounds...
I had in plans to power it up last week but i resigned from converting my power supplies.
Currently waiting for PSU from Banzai, which should send it tomorrow or on a days.
Then i'll be testing it
I build one and finishing second.
I changed 3.3uF cathode cap for double  bipolar 10uF. Finally i couldn't fit 3.3uF...
Second will be without cathode cap and with pot instead cathode resistor.
I will make comparison of cathode toplogies and resistor values, then i will post some pics and final schematic
Overall the build is really simple and i used really small sized boards.
Version on the pic isn't updated with cathode caps.

 

[micaddict]

Hey Vili!
Thanks for interest

Probably you are the only one

Nope.  8)

 

[ln76d]

Ha! Am writing email to you currently

 

[AusTex64]

I'm watching....

I built mine with AMI transformers though - do I need to exit? 

 

[ln76d]

No Robert of course not
Stay with us
Please say that at least your PCBs are green

 

[rock soderstrom]

Hi, any news on this interesting project? Cheers

 

[seancook]

I've also been following this, seemed like an interesting build.
What was the end result like?

 

[gyraf]

....watching too...

 

[ln76d]

Sorry Guys for no update.
This project stuck like few others.
I need to build proper psu for a pair.
I tested it only for quick some time ago with a little bit different plate voltage and it works really good.
As soon as possible i will finish it nd update topic

 

[duantro]

What capsules are you using? Donor mics cheapos?

 

[ln76d]

It's 80's Unitra Tonsil MCO 52. Made in Poland under license of Germn MB Elektronik (currently MBHO or somehow related).
Here are some pics of it, as also response (with original shitty preamp):
www.monterdiy.net/charakterystyka-mikrofonow-mcu53mco52-firmy-tonsil-2/
Here's pic of original :
https://www.vintagetools.de/out/pictures/master/product/1/MBE_MBE500_1.jpg

Capsule is really great, pretty flat and very pleasant sounding with good preamp.
Once i made comparison with Otava MK12, using modified preamps and both capsules.
Defintely beats up MK12 capsule

 

[dasnevestheo]

Hello ! Any news on the projet ? Did you finished the mics and PSU ? I have a pair of pronomics that need a nex pcb...

 

[Vac11]

I designed pcb for this circuit and also psu pcb... I used 6s6bv tube.... Mic board fit well in pronomic scm1 style bodies (and Banzai sdc body as well) . Im just testing this mic in my studio. Im very happy with my existing results.

Milan

EDIT:
BOM for microphone pcb:
https://drive.google.com/file/d/1jp-YwGODGWi2Ha-c3zeUsFixIOSsRk0A/view?usp=sharing

BOM for PSU pcb:
https://drive.google.com/file/d/1t7lS-MIwGDW9pOQUDgv8nSpq9AIkecXG/view?usp=sharing

 

[Vac11]

PSU

 

[ln76d]

Hello ! Any news on the projet ? Did you finished the mics and PSU ? I have a pair of pronomics that need a nex pcb...

Yes i built this circuit 3 years ago, tested and forgot about it I had to use PSU for different project.
Milan remind me about it some time ago and designed boards for it but we changed tube for 6S6B-V.
PSU is based on LM317 for heaters and LM317HV/TL783 for plate voltage.
Definately talk with Milan about the boards, probably he have few more for sale.
Boards are great! Soon i will finish four of these mics. Then i will post here new schematic.

 

[dasnevestheo]

Hello everyone !
Can't find a decent PSU transformer (secondaries 100v and 9v). I have can get 120+12 but that would be quite a voltage drop isn't it ?
So if anyone knows a cheap source of those...
Thanks y'all

 

[Vac11]

Hi Theo,

try local toroid transformers manufacturer....
Secondary 1:.............. 100V (maybe even 110V), 300mA (with big reserve)
Secondary 2:...............9V, 500mA

I have some toroids with those specs. You can PM me as always

M.

 

[OneRoomStudio]

What mics are the PCBs designed for? Would this circuit fit in an Oktava MK-012?