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Author Topic: Oktava MC012 mods and info  (Read 3540 times)

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Offline Brian Skalinder

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Oktava MC012 mods and info
« on: September 23, 2003, 02:19:20 PM »

MOD 1

Thanks to Spott for finding this on DAT-Heads and posting it here:

While this is not too difficult a mod to perform, some reasonable soldering
skills are necessary.  If you've never soldered before, this is not the
time to learn as it would not be too difficult to short something out.  I
also recommend a soldering iron that comes to a fine point.  The mod is for
people who think their oktava mics are too bassy/boomy.  Here's how much it
rolls off the bass in the amplifier --as measured by John Kjoll.  Note --
with no mod the bass is 1dB down at 20Hz anyways.

Post mod:
1dB down at 100 Hz
2dB down at 60 Hz
3dB down at 40 Hz
5dB down at 20 Hz

You will be replacing the gate resistor.  The stock one is 680 Megaohms and
I replaced it with 100 Megaohms.  If I could find a resistor between 50 and
100 megaohms I'd try that first (John suggested 50 to me which would cause
some effects up to 200 Hz, I'd try a 70 if I could find one) as I think it
could stand to be rolled off even more.  Good luck finding resistors (in
all honesty, you probably won't).  And if you do find some, I'd like to try
further rolling it off so email me.  I used a 1/4 watt old style.  I think
the new styles are smaller and that up to a 1 watt will work.  The main
thing is that it is no bigger than a cylinder of diameter .14" and height
.4".

1.  Remove the body by screwing in the 3 screws about 4-5 turns.  Chances are
many of the screw heads came broken off, just because thats the way it is.

2.  Pull off the body with a back and forth twisting motion.  Be careful since
it probably will be stubborn and then pull off all of a sudden.

3.  Stand the mic on the XLR end and consider the more crowded side of the
circuit board.  At the top left there is a resistor.  On the top right there is
an equivalent resistor.  Between them there are 2 capacitors, a ceramic one on
top and a metal one on bottom.  The 680 Megaohm gate resistor is the one on the
top left.  It is in a vertical orientation if the mic is standing on end (IE the
XLR side resting on a table).

4.  That top left resistor is the one you want to replace.  Please note that it
is connected to the other side by a white wire (at least mine was white but
these things have all different parts so YMMV).  I got rid of the wire and put
in the new resistor on the other side of the board since it was easier (or was
it:).  Take your new resistor and bend the leads at 90 degree angles and snip
to size.  Get solder all over both ends.  If you put it on the less crowded
side like I did, just be aware that you'll probably desolder the lead to the
capsule connection (it will go "fling" and spring loose) as you try to solder
it in.  In addition you will kind of need to push that (I believe capacitor
also, in one of my mics it was a hollow cylinder, and I can't remember on the
other since its not here but it will be obvious) thing to the left a little to
make more room if you do decide to put it on the less crowded side of the
circuit board.  Don't worry just be patient and resolder everything together.

5.  Make sure you get a good connection and not just a cold solder.  Replace
body and turn screws counterclockwise.  Make sure the resistor is not touching
the sides of the metal sleave (I don't think this actually matters but I like
to have everything isolated from everything).  Making sure of this is kinda a
pain, you may have to cut your resistor leads shorter and start over, etc.  
Actually now that I think about it this mod was kinda a pain in the ass, took
a while, and pissed me off.  (don't let that discourage you though).

I was running my mics with one modified and one stock for a few shows and
while I never kept track of which was which (for a while I had misplaced my
other 100Megaohm resistor so I couldn't even do both) I noticed that one
channel always had lower bass boom than the other.

The mod will not change the sound dramatically but enough.  Like I said before
I would try to find something less than 100 MOhm and roll it off a little more.

Please if you do this, let me know what you think,

Do at you're own risk and if you screw it up don't blame me


MOD 2


Thanks to fstrthnu2 for scanning this article from Recording magazine:

[ link forthcoming ]


ADDITIONAL INFO


Thanks to Simp-Dawg for this information from a discussion with Taylor from the Sound Room, a US provider of matched Oktava MC012s:

okay, after talking to taylor at the sound room, here is some further information and insight into the oktava mics.

> it's
> rumored that the people who put the oktavas together
> will often substitute any old part for the recommended
> component if they don't have it right there.  as such
> some of the mics are made with inferior (or even
> incorrect?) components.  do you know if there is any
> truth in this, and how does your quality control
> differ from it?

Quote
The Oktava plant in Tula has been known to substitute parts for ones of
different values - YES. However their quality control has become better
now
and they do have access to better parts suppliers.

When we "match" a set of mics; we match the ma/p output of the bodies
in
milliamps, then we separately match the capsules for both MV/pa
(millivolt)
output and frequency response.

Then, we ship the sets together withabels on the bodies and on the
capsule
sets.

You see it is a nickel-plated diaphragm and it has a tendency to be a
bit
corrosive after about 7-10 years, as well as not passing the same
voltage
unless they are tensioned carefully.
We use the services of RTT - the owners of 1/2 of the Elation lab in
Moscow,
so we have Alexander Schribeman doing the testing and matching. He was
the
one who invented the MC012 and still owns the license.


> secondly, do the pre-amp bodies have to be "matched"
> as well or is it only the capsules?
Quote
Yes, the current bodies, while better are pretty easy to get two out of
5
that will be close in ma/p output - close enough to be within 10% of
each
other, but the capsules from OKTAVA differ tremendously.

> when i first bought these mics ~1.5 yrs ago, one
> of the preamp bodies was cosmetically and structurally
> inferior to the other.  you sent me a replacement but
> i have no idea whether you matched it and neglected to
> ask as i was so pleased with the service.
Quote
all of the pre-amp bodies we use here are between 11 and 11.1 millivolt
output. That means your bodies (if they both came from us) -even from
different "matched" sets - should be within 1-2%

> finally, for personal reference, are the -10dB pads
> matched also?
Quote
NO - and I would do everything in my power to NEVER use one.
> yikes...i've been using these quite often as the mics
> seem to be fairly sensitive.  what is "bad" about
> them?
Quote
They are a simple buffer-use capacitor design. About as sophisticated
as
using a steel collander (spaghetti seive) to make a shower head.
Capacitors
are not matched and they not only lower the signal strength, but affect
(color) the sound in un-natural ways.

> two new questions and then i will leave you alone for
> a while ;)
> 1. have you heard of the modification to the mc012's
> written about in the latest recording magazine?  any
> input on the benefits of this?
Quote
I am aware of many mods. First, based around the use of a Toshiba
2SK170-BL
FET for the front end. Scott Dorsey does some EXCELLENT mods
(kludge@xxxxx.xxx) and I had two of his bodies on my test bench for 3
years - also used them in the studio. Now that I make MY OWN mics
(totally
different electronics design and capsule design) these babies are with
Elizabeth in the Florida studio.
> 2. have you in fact researched, and would it be
> possible, to have "active" cables to go between the
> cap and the body?  similar to neumann km140's or
> schoeps kcy actives, i mean.
Quote
IMPOSSIBLE, OKTAVA electronics are not set up for this - the mod is
inconceivable without a complete redesign and all new housing and
capsule
mountiong system. It is not worth the time or effort except as a
"leraning
experience" in how to build an active front end for a microphone and
then
end up with something that sounds inferior to many other products out
there.

However, my own T.H.E. mic bodies ARE set-up for goosecks, knuckles,
collette cables, etc. We will bring out these accessories next year.


Regards,

Taylor

So there ya go....hope this answers some questions for you
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Offline pridix

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Re: Oktava MC012 mods and info
« Reply #1 on: February 02, 2012, 04:16:00 PM »
Nice explaination! Thumbs up for this
It's not a secret at all, Achtung ya'll

Mics: MM-HSLO (4,7k mod) , AT853(853-O, 853-H, 853-C, UE-C)
Cables: Naiant PFA, Hosa ATT-448
Recorders: Tascam DR-40
Playing Stuff: Onkyo (TX7630 & TX18), Magnat System 400, Tannoy Mercury M2, Mission M35

 

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