EmRR

anyone turn an Oktava MK012 into a tube mic?
« on: August 25, 2007, 03:39:32 PM »
I have one with a bad preamp, and in the course of debating the repair / upgrade, I wonder if I'm not better off using it as a tube mic platform.  New replacement preamps are so cheap, it almost makes no sense to bother with the fix.  In regards to a tube version, I don't see any specific mention of this particular mic in the mic mod meta.   Anyone gone there already, out of curiosity?
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde


rafafredd

anyone turn an Oktava MK012 into a tube mic?
« Reply #1 on: August 25, 2007, 05:51:45 PM »
It´s has a  pretty small body, but pencil types or nuvistors may fit.

Gus

anyone turn an Oktava MK012 into a tube mic?
« Reply #2 on: August 25, 2007, 05:56:01 PM »
I have not tubed mine.

The reason I have not tubed mine is a transformer like I would want to use is to big.   I guess one could have the transformer mounted in a box with a short cable to the body.  Schoeps did that with a microphone if what I have told is true.  

One 012 I fixed had a bad PNP one of the body holding screws was inside the body moving around.

EmRR

anyone turn an Oktava MK012 into a tube mic?
« Reply #3 on: August 25, 2007, 08:00:02 PM »
I have a Sylvania demo pack of sub-mini types to play with.   I was debating either hi-Z on a short captive cable to an outboard box or a dual triode with unbalanced cathode follower output.  Just seems like an inexpensive platform for experimentation, since it's already flakey and replacement bodies are cheap.    Starting from scratch is probably nowhere near as easy, and I have six working Oktava capsules.   I may just buy a new body and gut this one.    Mine are the very earliest imported versions (1996-97?) before any 'improvements' were put into the design.
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

skipwave

anyone turn an Oktava MK012 into a tube mic?
« Reply #4 on: August 26, 2007, 12:37:09 AM »
Interesting idea. You could try the Royer "Country Boy" mod. A 5840 cathode  follower with the transformer in the power supply case.

"Using the JT-16-A with "The Country Boy's Capacitor Microphone" (14KB PDF)"
Quote from: PRR
Now, maybe you don't, or shouldn't, grab the ribbon for far-harpsichord, nor the hot condenser for snare-kissing... yet often we do.

pucho812

anyone turn an Oktava MK012 into a tube mic?
« Reply #5 on: August 26, 2007, 01:49:48 AM »
could always do the royer SDC tube mod. It has the mic transformer in the PSU and uses the 5840 submini tube.
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

EmRR

anyone turn an Oktava MK012 into a tube mic?
« Reply #6 on: August 26, 2007, 03:08:20 AM »
I cracked it open and had a look at the space and the tube size; man it's tight in there.   Even changing to a 4 or 5 pin connector looks questionable.  Might have to be captive wired if I do this.  I have 6021's and 6111's to play with already, and both look fine for a gain stage followed by cathode follower output.  Not sure you can get the required resistor count in there though.  More cypherin' to do.
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

Rossi

anyone turn an Oktava MK012 into a tube mic?
« Reply #7 on: August 26, 2007, 04:30:48 AM »
Oktava themselves showed a tube 012 version at this year's Musikmesse. I don't know how they did it, though. If I remember correctly, the mic was the same size as the transistor version. BTW. 012s aren't as cheap as they used to be, at least in Germany. On the other hand, the quality seems to have improved.
"I am not a number, I'm a free man!"
"Hahahahaaaaaa!!!!!"

pstamler

anyone turn an Oktava MK012 into a tube mic?
« Reply #8 on: August 26, 2007, 01:50:40 PM »
Here's a question: What about turning it into a "periscope" mic? Saw the body at a 45 degree angle an inch or so behind the capsule (thus preserving the screw mount and contact hardware). Put a tube in the stub; mount the back end in a larger-diameter body, perhaps with a tapered top, that would have room for a decent transformer and connector. Rotate the stub so that it matches the bottom half, but with the capsule now pointed to the side. Weld. You now have a periscope mic.

Peace,
Paul

EmRR

anyone turn an Oktava MK012 into a tube mic?
« Reply #9 on: August 26, 2007, 02:33:17 PM »
Yeah Paul, why not?  

Not sure I want to go there though.

I just had a look at the Altec M-20 and M-30 systems, and realize that everything but the capsule and tube is in the outboard PSU box.  That system has a captive 10 foot cable with a 5840 cathode follower.  They give resistor strapping info to use either of the capsules, where one requires 60V polarization and the other 200V.  One could add a switch in the 525 PSU for that, but you'd probably blow up your 60V capsule when you forgot.  

Need to measure the Oktava polarizing voltage.  This may turn into a modified Altec clone with Oktava capsules.  

The 'Country Boy' project is pretty much an adaptation of the Altec system; I haven't seen the original article to know if Royer mentions that.  

I suppose the cathode follower at the capsule is a better impedance match; I was neglecting to think about that part.  There are tube mics with gain stages at the capsule; I need to have a look at the differences and see how critical it is.
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde


dale116dot7

anyone turn an Oktava MK012 into a tube mic?
« Reply #10 on: August 26, 2007, 10:59:00 PM »
I haven't turned an Oktava into a tube mic but I have built the Altec 525 power supply for a tube mic using the 5840 tube. It works well. The M11 (6AU6), and M20 (5840) are both cathode followers. They are sensitive to moisture on the capsule - maybe a bit more sensitive than some mics. They self-bias (no grid resistor).

mick

anyone turn an Oktava MK012 into a tube mic?
« Reply #11 on: August 27, 2007, 06:27:06 AM »
Hi Doug, I think this is the royer article that you are talking about (but I'm not sure)

http://www.twin-x.com/groupdiy/albums/userpics/tape_op2.pdf

Rossi

anyone turn an Oktava MK012 into a tube mic?
« Reply #12 on: August 27, 2007, 10:51:10 AM »
Quote from: "emrr"

I just looked and can't find any mentions about an official version; any pointers?


look here, next to the hammerheaded figure 8 adapter. I don't think you can actually buy those, yet.

http://www.oktava-online.com/
"I am not a number, I'm a free man!"
"Hahahahaaaaaa!!!!!"

skipwave

anyone turn an Oktava MK012 into a tube mic?
« Reply #13 on: August 27, 2007, 12:15:07 PM »
Quote from: "emrr"
The 'Country Boy' project is pretty much an adaptation of the Altec system; I haven't seen the original article to know if Royer mentions that.


Yes, he certainly does. It is just the M20 circuit at a different operating point, less than half the B+ voltage. I built it into an MXL v57m, and I like it.
Quote from: PRR
Now, maybe you don't, or shouldn't, grab the ribbon for far-harpsichord, nor the hot condenser for snare-kissing... yet often we do.

skipwave

anyone turn an Oktava MK012 into a tube mic?
« Reply #14 on: August 27, 2007, 12:20:50 PM »
Quote from: "Rossi"
Quote from: "emrr"

I just looked and can't find any mentions about an official version; any pointers?


look here, next to the hammerheaded figure 8 adapter. I don't think you can actually buy those, yet.

http://www.oktava-online.com/


The link is broken, 404 error:

http://www.oktava-online.com/mkl012.htm

It appears in the navigation bar on the left, under "Tube Microphones," but no page.
Quote from: PRR
Now, maybe you don't, or shouldn't, grab the ribbon for far-harpsichord, nor the hot condenser for snare-kissing... yet often we do.

Rossi

anyone turn an Oktava MK012 into a tube mic?
« Reply #15 on: August 27, 2007, 01:48:01 PM »
Same here. As I said, I'm not sure the mic is quite ready yet. But the website is not particularly well coded (or proofread).
"I am not a number, I'm a free man!"
"Hahahahaaaaaa!!!!!"

EmRR

anyone turn an Oktava MK012 into a tube mic?
« Reply #16 on: September 01, 2007, 11:33:41 AM »
Wow.  $1150 street price for the tube MK012.    Out comes the dremel.....
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

EmRR

anyone turn an Oktava MK012 into a tube mic?
« Reply #17 on: September 12, 2007, 03:40:21 AM »
Body disassembled and new circuit board (really a spacer / tube holder) cut to fit.  Have to drill the mounting holes and it's ready to go back together and slap the tube around (I mean in).  

Swapping the XLR is a PITA.  Russian part not exactly identical to Switchcraft (no surprise) and requires some carving and swapping of the ground lugs.  

Had to grind one body fastening screw shorter on the inside as it was striking a new XLR pin and wouldn't go in far enough to get the body back on the connector case.  

More or less following David Royer's cathode follower plan as example with glances at the Altec information.  David informed me the Oktava capsules seem to not like polarization over 40-45 volts, so going to shoot for that range.  

Will see if I get happy with the 5977 tube first, because I have two laying about already.

Audio transformer I'll try first in the PSU box will be a Jensen JE-6110K-A    150:10K mic input, but run backwards.    Again, because I have a few waiting for a reason to live again.   That's the input transformer from the Auditronics 110B input module.

Looks like my available project case for the PSU is a GE SS broadcast monitor amp case, pulled from the scrap pile.  It's big enough to handle at least two mics worth of ins and outs should I decide to mod both my Oktavas.    Has plenty of space to separate power transformer from audio.
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

skipwave

anyone turn an Oktava MK012 into a tube mic?
« Reply #18 on: September 12, 2007, 12:18:17 PM »
Cool. Thanks for the progress update.

Quote from: "emrr"
David informed me the Oktava capsules seem to not like polarization over 40-45 volts, so going to shoot for that range.


What Rk are you using? I saw several different values for Rk in the different iterations of Royer's version. Since I used a large diaphragm I went with the highest, 47k.

http://www.groupdiy.com/index.php?topic=19546&postdays=0&postorder=asc&start=15
Quote from: PRR
Now, maybe you don't, or shouldn't, grab the ribbon for far-harpsichord, nor the hot condenser for snare-kissing... yet often we do.

EmRR

anyone turn an Oktava MK012 into a tube mic? New
« Reply #19 on: September 12, 2007, 12:30:56 PM »
Thanks for the link!   I'd seen and lost track of that commentary.

I'm not using any particular B+ or Rk yet; will futz about when I get some electricity flowing.    The 39K is the right direction.  I'll probably play with a pot first and look at some measurements.

I noted after my last post that the Royer plans are using various low ratio transformers.  I have a ton of options to try there, but the 10K:150 struck me as a best first choice and I'm not particularly worried yet about the losses there.
« Last Edit: December 18, 2012, 11:42:59 PM by emrr »
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde


 

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