R/E/P Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1]   Go Down

Author Topic: SOny C-37A power supply  (Read 1709 times)

piedpiper

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 87
SOny C-37A power supply
« on: July 11, 2010, 02:07:23 am »

I have a Sony C-37A that needs a power supply. They appear to be quite difficult to find. Any thoughts as to who might be the best person to recreate one? Or what output transformer would best suit since that is incorporated in the power supply?
Logged
Tim Britton

row, row, row your boat...

Fletcher

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3016
Re: SOny C-37A power supply
« Reply #1 on: July 11, 2010, 09:40:42 am »

You might want to talk to David Josephson - he seems to know more about C-37A's than anyone I have ever met [or at least he has spoken about them with authority more than anyone else I've ever spoken with about those mics].

Peace.
Logged
CN Fletcher

mwagener wrote on Sat, 11 September 2004 14:33
We are selling emotions, there are no emotions in a grid


"Recording engineers are an arrogant bunch.  
If you've spent most of your life with a few thousand dollars worth of musicians in the studio, making a decision every second and a half... and you and  they are going to have to live with it for the rest of your lives, you'll get pretty arrogant too.  It takes a certain amount of balls to do that... something around three"
Malcolm Chisholm

piedpiper

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 87
Re: SOny C-37A power supply
« Reply #2 on: July 11, 2010, 04:38:51 pm »

Thanks! Will do.
Logged
Tim Britton

row, row, row your boat...

radiovinheta

  • Full Member
  • ***
  • Offline Offline
  • Posts: 156
Re: SOny C-37A power supply
« Reply #3 on: July 12, 2010, 03:27:26 pm »

Not sure, but it seems that in C37A the power supply also contains the transformer mic amp and a part of the amp, unlike other tube microphones....
Logged

J.J. Blair

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 12809
Re: SOny C-37A power supply
« Reply #4 on: July 12, 2010, 03:40:29 pm »

Radio, basically yes.  The C37A uses a cathode follower amp, and the tube is in the mic, and the transformer is in the PSU.  Additionally, the transformer coupling cap is in the PSU, and it's that circuit that is used for the low end attenuation (V, M1, M2).  It adds capacitors in series as part of a RC HPF circuit, which you can see below.  

http://www.freeinfosociety.com/electronics/schematics/audio/pictures/sonyc37a.gif
Logged
studio info

They say the heart of Rock & Roll is still beating, which is amazing if you consider all the blow it's done over the years.

"The Internet enables pompous blowhards to interact with other pompous blowhards in a big circle jerk of pomposity." - Bill Maher

"The negative aspects of this business, not only will continue to prevail, but will continue to accelerate in madness. Conditions aren't going to get better, because the economics of rock and roll are getting closer and closer to the economics of Big Business America." - Bill Graham

radiovinheta

  • Full Member
  • ***
  • Offline Offline
  • Posts: 156
Re: SOny C-37A power supply
« Reply #5 on: July 12, 2010, 03:47:01 pm »

About C37a, it has a level of output as low as C37p or its output is hotter?
Logged

Fletcher

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3016
Re: SOny C-37A power supply
« Reply #6 on: July 16, 2010, 02:57:07 am »

The output level on the C-37A is low in relation to most things Neumann [like the C-37p], but that generally doesn't bring an elevated noise level unless there is a problem with the amplifier.

Peace.
Logged
CN Fletcher

mwagener wrote on Sat, 11 September 2004 14:33
We are selling emotions, there are no emotions in a grid


"Recording engineers are an arrogant bunch.  
If you've spent most of your life with a few thousand dollars worth of musicians in the studio, making a decision every second and a half... and you and  they are going to have to live with it for the rest of your lives, you'll get pretty arrogant too.  It takes a certain amount of balls to do that... something around three"
Malcolm Chisholm

djosephson

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 55
Re: SOny C-37A power supply
« Reply #7 on: July 22, 2010, 06:57:09 pm »

Sorry again Fletcher, we don't make power supplies for mics. There are quite a few folks who do, though, and the requirements aren't that critical. The schematic JJ Blair posted in this thread looks right to me. If your power supply maker doesn't understand what's going on with the voltage dividers in the B+ and heater circuits (ask them to explain it), find someone who does.

Quote:

or at least he has spoken about them with authority more than anyone else I've ever spoken with about those mics
...that's just because I've dissected enough of them (mostly broken ones!) in the process of understanding them well enough to replicate the acoustic design of the capsule. Originally this was for the Groove Tubes MD-3 mics and with some more refinements our C715. We didn't use anything from the power supply though.

The power supply of a C37A makes about 160 volts B+ if I remember correctly. As shown in the diagram, the heater is fed 6 volts DC, floating at about half the B+ or 80 volts above ground. This approximately sets the capsule polarize voltage which is tapped off the cathode. The C37p does it entirely differently with a separate dc-dc converter.

The audio output stage is just a coupling cap (switchable to determine the low frequency rolloff) and a transformer, which I think is around 4:1. This produces a low output level (since it's already coming from a nominally unity-gain cathode follower amp) but that just means you need a little more gain in the preamp. Cathode followers don't like to see much load, so an impedance step-down is needed, and with that goes a drop in voltage.
Logged
--
David Josephson -- Josephson Engineering Inc -- www.josephson.com

Pages: [1]   Go Up