Some questions about the Sony C37a - mics with cathode follower

[k brown]

Well the capsule isn't like any other and is not similar in sound to any european capsule. Sony's original intent was to create something like the U89 but a tube mic. I believe Josephson and I are the only 2 companies producing versions of this capsule. The sound is boring to say the least but they make a U89 sound exciting. The first time I heard one of these mics I thought it was broken.

The real shame is that it is easy to make this capsule sound similar to a CK12 if it is set up right but then it wouldn't be as Sony intended.

If you want to build a copy and can't get the right capsule you could probably use the K89.

Is Royer using Josephson's capsule for the MA-37?

 

[Tim Campbell]

Yes. They initially approached me but I was not interested in building this at that time. I prefer to work on capsules that I really like.

 

[k brown]

Yes. They initially approached me but I was not interested in building this at that time. I prefer to work on capsules that I really like.

Snap!

 

[rock soderstrom]

I love mine

Ahh, a real user. What do you use it for? What do you like most about the C37a?

 

[rock soderstrom]

If you want to build a copy and can't get the right capsule you could probably use the K89.

What about if youre going for a "new" sound? Im considering building a CF mic body and trying out a bunch of different capsules to find something... interesting! Maybe start with a CK12 and one of queens flat47s.

I think copying or even cloning only makes sense if you have the original components. I don't have them, my goal is a good sounding microphone. I will try many things on it.

I love simple circuits. My last experiment was a Sela T12/24 inspired project.

One consideration was to build a mic with a 6j7 steel tube, see the other thread.

Here the mentioned CF advantages would free the necessary space in the microphone for the gigantic octal tube.

Maybe I'll take an EF94 after all, we'll see.

To me this circuit seems well suited to compare different capsules.

 

[rock soderstrom]

That gubbin on the back of the head basket is not a switch; it's simply the access hole for the mechanical 'vane' on the back of the capsule that seals off the rear vents when set to omni. A flat head screwdriver goes in there. Scares the hell out of a lot people to poke a screwdriver into the back of a condenser mic - especially a vintage one

Wow, interesting.

 

[rock soderstrom]

Great mic, these days one could sound different from another c37, simple circuit high headroom, small for a tube condenser, since they moved the output transformer and hpf to the psu. B+ measures 247v on mine. 6au6 tubes are not expensive but it does require a quiet one, so going nos you’ll want a few to listen to. They did change the psu over the years as well as the output transformer I believe, the cp-2 psu has a 10k:600 opt ratio 4.08:1

Yes, OPT is 4:1 according to Jakob's sketch. You could even use an Edcor 10k:600 if you put enough distance between the OPT and the power transformer. Shielded would be better of course.

Thanks for B+ info! I haven't done the math yet but it seems to result in quite a high polarization voltage for the capsule.

That should be taken into account in any case!

 

[rock soderstrom]

Can also do without a transformer, and just go impedance-balanced. CF can drive cables on it's own.

Simplicity and low component count ,
I did a version of the B&K cf circuit with only the tube , capsule and grid resistor contained in the mic body , everything else was back at the psu end ,
As I said on a post previously I tend to take the cf output directly to the grid of the following preamp tube , 1M ohm input z , and plenty of headroom .

Interesting. I have read that elsewhere as well. Seems to work well.

The few in-body components are a real advantage. All components fit easily on the socket of the tube.

 

[k brown]

I've built three CF mics Royer-style. Oktava MK-012 with 6205 (same as 5840), Oktava 219 capsule in a C-37A-style body with 6AK5, and an Oktava 319 with heavily modded/deadened body with 6AU6. Royer has said that 5840, 6AK5 and 6AU6 when triode-connected, all have similar characteristics.

All were fine with whatever grid-leak polarization the circuits put on the capsule (didn't have the instruments to measure).

 

[rock soderstrom]

Years ago I built a mic very similar to the C37 using a russian 6J4P and a CK12 capsule. It sounded brilliant.

I'm not surprised that I'm not the first to have the crazy idea of putting an octal tube in a microphone. That's my plan!

 

[rock soderstrom]

Nice video from Mojave with a lot of info.

 

[volker]

I'm not surprised that I'm not the first to have the crazy idea of putting an octal tube in a microphone. That's my plan!

You might be looking at the wrong tube. I would think that Tim used this Russian tube, which is an equivalent to the 6AU6/EF94.

 

[Recording Engineer]

Back in 2015, I had the idea of a C37A-inspired mic. I had the option of C800 or C37B capsules. My take-away is that the C800 capsule is more of an “improved/modernized” capsule and the C38B is much closer to the C37A capsule. I went with the latter.

Interesting gyraf and Tim find this type of capsule inferior to the rest of the classics, but I find otherwise; definitely cool and different.

After brainstorming with Chris at Barbaric, he built me a pair of mics. Typical 60V to the capsule. We chose the 5840 instead of the 6au6, went with an OEP A262A3C transformer (I’m pretty sure it’s 4:1), and an MXL CR77 body. Certainly a special combo! We tried other transformers, but nothing as special. I also have a pair of mics in with the same circuit, but with Electro-Voice RE200 capsules and in Sterling Audio ST31 bodies. This made the extremely-bright capsule to be extremely-balanced.

Chris has made a number of these mics with good edge-terminated k67/87 variations, with great success. True CK12 -types or a k89 as suggested would definitely be super cool!

 

[Recording Engineer]

 

[rock soderstrom]

You might be looking at the wrong tube. I would think that Tim used this Russian tube, which is an equivalent to the 6AU6/EF94.

The radiomuseum.org made fun of me, they describe the tube as an octal version.

https://www.radiomuseum.org/tubes/tube_6j4p~2.html
Also elsewhere the 6j4p is described as an octal tube, then again there are places where this designation stands for the Russian EF94/6AU6. Maybe a translation error from the Russian language?

I think you are right.

 

[rock soderstrom]

After brainstorming with Chris at Barbaric, he built me a pair of mics. Typical 60V to the capsule. We chose the 5840 instead of the 6au6, went with an OEP A262A3C transformer (I’m pretty sure it’s 4:1), and an MXL CR77 body. Certainly a special combo!

Fantastic work, these are very nice microphones!

In my research last night, I quickly came to a very similar / identical housing. Thomann puts a condenser (SC1200) and a ribbon mic in a very similar body which in turn reminds me of the C37a. Good choice, at least visually!

It would be interesting to know who the original manufacturer of this is in China and whether you can buy individual body shells.

Chris has made a number of these mics with good edge-terminated k67/87 variations, with great success. True CK12 -types or a k89 as suggested would definitely be super cool!

Exciting, I want to try some capsules from the same background. The first tests I will do with this cheap edge terminated China capsule.


Thanks for inspiration!

 

[Tim Campbell]

Interesting gyraf and Tim find this type of capsule inferior to the rest of the classics, but I find otherwise; definitely cool and different.

Did you have these capsules re-membraned? If anyone has worked on the capsule the sound can change dramatically. As I said they can easily be adjusted to mimic CK12's.

I meant the Russian equvilent of the 6AU6. I prefer the sound of the russian tubes over standard 6AU6's

A picture of 1 day's work last year.

 

[Recording Engineer]

Did you have these capsules re-membraned? If anyone has worked on the capsule the sound can change dramatically. As I said they can easily be adjusted to mimic CK12's.

I meant the Russian equvilent of the 6AU6. I prefer the sound of the russian tubes over standard 6AU6's

A picture of 1 day's work last year.

That picture is a heart-stopper, Tim. Oh how I long for 1 or 2; whenever you could!

Mine are still stock membranes. I ordered by phone from Sony USA Service Plus. They were back ordered, but shipped within a few weeks to me in CA from Laredo, TX.

 

[Tim Campbell]

These membranes are not pre tensioned though. If during installation they are tuned to a different frequency they will sound radically different. Have you done a comparison wth your mics and original Sonys?

 

[Recording Engineer]

These membranes are not pre tensioned though. If during installation they are tuned to a different frequency they will sound radically different. Have you done a comparison wth your mics and original Sonys?

Unfortunately, no. I’ve never known anyone with a C37A or C38B to trust me with it or play at their place. Maybe I’ll grab a C38B just for kicks sometime soon. Been thinking about it a long time.

I should throw up a Rhodes sample I did a week ago with them. Alongside an Audio-Technica boundary on the tines board, it was very nice!

Love them on male and female vocal. Clean electric too. I should grab a sample of that too. I’ve been hearing the past year about a trumpet player’s project coming in, but still nothing there. I wish. I only tried it once when I first had them, but at tom-height I’m front of the drums,, as wide as the drums, turned to reduce as much hi-hat and cymbals as possible, nothing like it! In fact, this has inspired me to do it again on my next drum session and see if it’s as good as I remember!