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

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craigmorris74

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I'm about to start building this mic and have a couple of questions:
1. Could I use a Primo EM-21 electret capsule for the project? If so, should I modify the build to suit it?

2. I have a generic Chinese PSU in the studio. Can I adjust it for 100V and 6V and use it with the mic? I intended to build the PSU on the board I bought from Milan, but I'm having trouble sourcing the toroid to use with it.

Thanks,
Craig
 

Vac11

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Hi Craig:

1) polarisation voltage of s52 mic is 50V, electret capsule doesnt need it. Im not sure if its possible join this tube circuit with electret capsule. Search for 'countryman' microphone circuit (- tube circuit with electret capsule and Jensen transformer).

2) yes you can use your psu. For transformer you can check m49 thread. There are some possibilities in BOM. In any case you can use mic with 120V on B+.

Best

M.
 
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craigmorris74

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Thanks for the reply, Milan!

I'll probably just use one of the 3U cardioid flat capsules for this one.

Is there any advantage or disadvantage using the mic with 120V B+?

Thanks,
Craig
 

k brown

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Just a reminder for those who may not know - 6205 is same tube with slightly different pin-out; sometimes easier to source than 5840.
 

Tubetec

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Ive used the 5840/Ef732 , rock solid performer , only ever in cathode follower config though , wouldnt mind trying anode loaded version .
 

rock soderstrom

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would be cool to know. I haven't built my mic yet, but have a TEAC mic with an EM21 and and old MXL that are ready for new guts.
I got similiar mics for dirt cheap. I want to test the differences betwen FET with P48V, Country Boy and S52 circuit.👍
 

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rock soderstrom

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I think it should work. Imho C2 is not needed. Check 'country boy' microphone schematic for inspiration too.
Thanks for feedback!👍

I am coming from the Country Boy circuit, a cathode follower with gridleak biasing.

The next step for me is to check the S52 circuit in this down stripped version. I call it the "skinny S52" circuit. AFAIK, this is the most basic tube head amp and thus the ideal canidate for a SDC mic with an electret capsule.

I am kind of uncertain about the grid biasing resistor. I am still a mic builder newbie and do not really know how to calculate them.

So my question, what effect does the value of the grid resistor have on distortion, noise, headroom and sound? How should I bias this for an electret capsule?
 

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craigmorris74

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I built second S52 microphone. Thank you Piotr for great design and all tips. For this mic I used 10pF C0G feedback capacitor for lowering the output of microphone. In C1 position I choosed 3n3F cap and in C2 1nF capacitor. R3=100M and plate R6 resistor 200K. Im going to build another two microphones.

Stock BM80 (and also Pronomic) capsule sounds a little bit "harsch" compared to Maiku SDC capsule. Cant recommend Maiku SDC capsules more. Capsules from Banzai´s KM84 body kits fit on ISK BM80, Pronomic SCM-1 bodies...

Here some detailed photos:
Did you end up preferring the version 1 or version 2 schematic with this mic? I'm about to build mine.
Thanks,
Craig
 

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