"U67"-ish microphone

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Wow great thanks for your answer. I still got 2 of those psu's laying around.

Changed the 72V Zener to 62V zeners.

A chance to get the pcb's allready? if you could put up a BOM that would also be nice. Maybe a few more pictures from the mic, if possible. Would love to build one since i'm in need for a different descent tube mic, i'm over here in germany, been to the netherlands pretty often.

Regards
 
I had a few PCBs made, but they have all been sold now.
And about the bill of materials: there isn't much in the circuit, so the fastest route is to write down the needed components yourself.
The only 'difficult' parts are the high-value (G.ohm) resistors. (Not every electronics store has them.)
 
RuudNL said:
The only 'difficult' parts are the high-value (G.ohm) resistors. (Not every electronics store has them.)
Fanell have them at a reasonable price:
https://fr.farnell.com/te-connectivity/rgp0207chk1g0/resistance-couche-epaisse-1g-10/dp/2805261
They also have 10, 100, 1 000 and 10 000 Gohm at unrealistic prices!
https://fr.farnell.com/ohmite/um050e100bke/res-10000g-3w-radial-thick-film/dp/2944974
 
This Cascade Elroy power supply I bought for cheap will work, right? I’m pretty sure it’s 120v B+ and 6.3v for the heater. 
 

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I would measure the +HT output, just to be sure.
The polarisation voltage on the capsule is ~½ of the +HT voltage.
More than 60 volts on the capsule is probably a bad idea...
(If the voltage is more than 120 Volts, you can always change the zener diodes in the power supply.)
 
Big Thanks to Ruud for this awesome project. It sounds great. Ruud you are a prince.
Here is a picture before wrapping it up
 

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Thank you, that capsule waited 17 years in my mic locker for your project to come along.
Well worth the wait.
 
It depends a bit upon the tube.
HT from the power supply is +120 Volts.
This voltage was chosen so that you can use a standard commercially available power supply.
Plate voltage is usually in the order of 55-60 Volts.
Plenty of headroom anyway!
 
I want to try one of these as soon as I can free up a suitable donor body.  With the smaller transformer, this should fit into something like an MXL 2010.  The larger SYT-5 bodies have been out of stock for so long (even the budget YT5 now) that an alternative design like this one is a great option to have.
 
Take care that you use a microphone capsule with a single backplate.
Sometimes capsules advertized as ' K67' seem to have isolated backplates.
In this case you have to connect both backplates together.
 
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Thanks RuudNL!

Have just been waiting for this. Will start a project with two vintage M7 capsules reskinned by Thiersch.
I was wondering which caps to spend on C8....? I will not have any size restrictions as I am building in a rather large brass cylinder.
I am thinking Mundorf alu in oil and then maybe a Lundahl LL1578XL 10:1.
/Robert
 
Why use M7's with U67-ish electronics (which include high-frequency attenuation)? How dark / dull are you hoping (or intending) those mics to be?
 
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