S316 - tube microphone project (K67, EF86, 10:1, variable polarisation voltage)

[ln76d]

[PROJECT FINISHED]

Last design this year

Cardioid only.

Capsule 35mm SE Electronics K67
Tube EF86 Lorenz NOS (really good 86 - sounds better than TFK).
Transformer Beyerdynamic BV310 1:10 (used with reversed sections).
C1 mustard cap, C2 Elna silmic II, C3 Philips "orange" MKP, C4 Wima MKS (old one not MKS2)
R1/R2 KEW-0.5, R3/R4 Beyschlag carbon.
Donor body is MXL2001 type.

I resigned from two microphones circuits build so i had some free parts to reuse - donor body etc.
I used only things which i had at home.

Merry christmas!

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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

 

[ln76d]

PSU

It can be used with any chinese power supply.
I used typical enclosure like hst11a and PCB from SCT700.
Transformer 175VAC/15VAC

Grounding:
- heater have separate ground track at pin7.
- main circuit ground is connected to pin1
- body/shell and transformer shell/static shield are connected to xlr body (cable shield).

There's no connection between these three grounding points inside microphone (simply - no connection of circuit ground to the body). All three grounds are connected together inside PSU at XLR housing connector.

For typical chinese 7pin cable check is there connection between shield and any of pins. In cable which am using there was connection between shield and pin7 from both sides of the cable. I removed both jumpers.

Polarisation voltage from ca. 44V to 72V in six steps.
It acts like pad and change also response (for some capsules more for some less - depends on capsule tuning).


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    II

 

[micaddict]

Picea abies

 

[ln76d]

slasha backslasha paralitica ;D

 

[micaddict]

Yeah, that's a subspecies.

 

[dchang0]

Very cool! Much simpler than the U-67 schematic that I am considering building next.

If you could post up any audio clips that would definitely be awesome.

On a side note, may I ask what schematic drawing software you used for the S316 schematic?

 

[ln76d]

Yeah definately much simpler
Also different sounding
Someday i will publish all my microphones sound samples, but definitely today is not that day
When i finally open my studio then there will be occasion to make different samples.
First schematic which i did few years ago was made with free eagle. From that time i'm using ms paint to change layout

 

[dchang0]

Cool--thanks!

EDIT: I'm trying out EAGLE (Freeware Edition) from cadsoft.io, and it doesn't seem to have the EF86 pentode that is in your schematic. Did you get a custom symbol from some library somewhere?

That is the best EF86 symbol I've seen anywhere (it has the tube shield on pin 7!).

 

[ln76d]

On all of my schematics pentode is just simple pentode from some library found over the web.
Pin 7 is just made in paint
Same with all markings.

 

[dchang0]

Ohhhhhh, that's how you got the pin 7 shield...

Dang. I was hoping somebody had actually made a symbol with the shield (as you can tell, I'm a huge EF86 fan).

 

[ln76d]

Ohhhhhh, that's how you got the pin 7 shield...

Dang. I was hoping somebody had actually made a symbol with the shield (as you can tell, I'm a huge EF86 fan).

Try E80F in place of ef86

 

[Gus]

Zebra50 posted a build in the past at this site
IIRC
A WE body with a Royer circuit
Power supply had variable capsule and heater voltages
I have not found the thread anyone remember what to search for?

 

[ln76d]

I never saw it, so don't know.