Sony C-37A clone

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abechap024

Well-known member
Joined
Aug 8, 2009
Messages
2,303
Location
Provo, UT
Hi here I had some crap mics laying around and decided to try to make a Sony C-37a clone. It was really simple to make and sounds much better then stock. Only one capacitor in the signal path, and if you wanted to be a turd you could probably drop that cap too. I followed the schematic exactly except for substituting a 1g resister for the 100m resistor
sonyc37a.gif

The build is dirty and quick but it works. And the audio file is lightly limited with an L2.get over it.
The differences in the mic are not as obvious listening on my laptop speakers. The overall clarity of the mic has improved and the mid range is cleaner and the tonality has improved.
For me its made a totally useless mic at least semi useful.


I would recommend this mod, it was fun! ;D

pictures of the beast
http://img709.imageshack.us/gal.php?g=dsc04708o.jpg

sounds of the beast
http://www.mediafire.com/?zem4lmyk4nm


 
cool!

thanks for posting the mp3 - it's seems strange to me that we only ever see pictures, very rarely do we here SOUNDS - and that's what it's all about no? haha

although it's little hard to compare in the mp3 - sounds like you are further away and speaking more loudly in the "unmodded" part? - and maybe the "modded" is a bit louder/L2'ed? i know how hard it is to keep that kind of thing consistent.... the modded does sound nice though!

thumbs up.
 
Hi!

Just wondered what output transformer did you use for this?

abechap024 said:
I followed the schematic exactly except for substituting a 1g resister for the 100m resistor

Could you post up a few measured voltage readings, for example at the cathode & anode. Did you use the tube rectifier? I couldn't see it in your PSU.

z50
 
Opps! yea sorry,
I guess i didn't follow the whole schematic, the power supply was just whatever I could scounge up at the moment. Haha I think the capacitors i used came from an old VCR! Anyway I used a PM 1000 input transformer I believe they are something like 1:6. I just wired it backwards so it was a step down instead of a step up.
Yea the sound examples aren't perfect. I recorded the unmodded ones a couple months ago and Don't remember how close i was to the mic. And listening to the sound samples on the laptop it sounded like the modded file might of been pushing the l2 a little more. but I think the sound quality differences are there. I E to me the tube mic does sound rounder and slightly fuller natually compressed so a little louder. A thicker tone for sure. Anyway yea the power supply pics doesn't show the transformer in there either, I guess I'm a pre mature picture:p and the power supply takes off of gyrafs idea of using 2 transformers instead of a voltage doubling or tripling circuit for the high plate voltage. I used a 120:16v transformer that feeds a rectifier for the 6.3v heater (lm317) and another transformer ~12v:120: this second transformer was really small, you could pull one out of an old cellphone charger because of course the plate doesn't need much current. I rectified the 200 something voltage with standard diodes and put it through a couple smoothing capacitors and an inline resistor and then another capacitor. I believe its sometimes referred to as a resistor capacitor regulation power supply in some electronic books
I have another microphone that I'm going to wire up with this circuit so I can have a stereo pair of these mics I just need to get my hands on another pm-1000 tranny.
 
Would be nice to get some measured voltages from a good working C37A (original circuit) and add those
numbers at key points in the schematic so there is a general idea how this circuit behaves. This way when
anyone decides to build a non-vacuum tube rectified power supply like yours it also can behave similiarly or
with upgraded performance.
 
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