Oktava MK012 low-cut filter self noise

Throwback

Throwback

Well-known member
Have just received a MK 012 today - the movie set version - and have spent the evening putting it through its paces on a boom. Generally pretty much as expected (and handling\wind noise slightly less than feared), but have been surprised by the additional self noise introduced by the low-cut pad included. It is surprising that such a simple device can add this noise (you can see two components - one at least a capacitor - through the transparent cover). The noise is sufficiently noticeable that I wouldn't want to use the low-cut pad, and, as I boom via a Sound Devices MM-1, I have a good alternative 80hz low pass filter, but - as I would prefer to cut the low frequencies at the mic and, even, be able to use both filters on occasion - I wonder whether others have listened closely to the mic with and without the low-cut pad and, if so, have noticed the unusual noisiness of the pad (I don't have the same problem with other mics). If not, l'll assume the components in mine are faulty and send it back to Germany (it came from reputable Oktava-online in Stuttgart) for a replacement. Cheers, Roland.
 
Update

Update

I emailed Oktava-online and received a prompt reply to say that the low-cut filter 'unfortunately it does add some noise', so it seems clear that there is no point exchanging it for another: the company has offered to take back the whole set or just the low-cut filter, but I am keen to hang to the mic and to explore the possibility of improving the low-cut filter before sending the latter back. I had suggested DIY swapping out the components - in case the noise derives from use of low-quality components - and, although Oktava-online wasn't too hopeful that this would help, they provided me with the values ('30 MOhm resistor and 1000 pF condenser'). It's a simple job to do with a soldering iron, but I wonder whether anyone with experience thinks a low quality resistor and capacitor could be to blame (an internet search has thrown up nothing on this) and, if so, what types would make the best quality replacements (e.g. a polypropylene capacitor)? Any help would be much appreciated. Cheers, Roland
 
I have never used the low cut on the mic. The one on the MixPre is more flexible, don't know if the MM1 has a low cut so that may not be an option for you.

Yes certainly the components can add noise, especially the capacitor (condenser) and the classic mods for the Oktava swap out some of those in the power unit. I have looked at the low cut filter and the soldering might be a bit tricky. Your going to want to use a very light touch so you don't melt the plastic. You might wat to talk to the folks at OKTAVA MOD and see what they recommend.
 
There are probably two things that are prime suspects to cause that kind of noise.
The first is low-quality components, which, alas, is a chronic problem with Oktava. (*)

That is why there are re-sellers who do additional Quality Control before selling them to end-users.
So, replacing the resistor and capacitor would have a good chance at mitigating that noise.
Of course, you must find good-quality parts to replace them with, or the effort is for naught.

I would at least consult the Oktava microphone experts on exactly what parts to use, or you
could just send it for "repair" to one of the Oktava specialists like Michael Joly at http://www.oktavamod.com/

The other prime suspect is leakage paths, specifically splattered solder flux or other dirt.
I would at least try to dis-assemble the pad and thoroughly clean all the plastic parts with a cotton swab and alcohol.
Note that because this is a VERY HIGH impedance circuit, even dirt you can't see could be causing problems.

(*) This was a big problem back during the Cold War when Soviet-bloc countries didn't have access to modern parts.
But from your report (and others) it seems like it continues to be a problem, which seems a bit surprising to me.
I guess Oktava is happy with making budget products and does not aspire to world-class.
 
I've never heard of a passive HPF adding audible noise, or enough to be a problem. As Noiz2 and Richard stated, the 'Micheal Joly' and 'Bill's Recording' mod should lower the self noise and tighten the low-end. Micheal Joly also offers a repair service. (non-warranty and different than the mod.)
Many purchase Oktava's from 'The Sound Room" ( www.oktava.com ) who hand picks, checks and tweaks the mics before shipping.. of course one pays extra for this service. AFAIK, The Sound Room does not offer the "Dorcey" type mod.

Oktava's quality control issue is/was well known, as were the Chinese 'counterfeits', though lately, both seem to be less of a problem. There's lots of information about this on the internet.. search
 
Scott Dorsey (of the famous Dorsey Mod) actually said that the ELECTRONICS part of the Chinese counterfeits appeared to be better than the genuine Oktava products. Likely due to better supply chains, better manufacturing techniques and better QC. But the Chinese capsules were inferior to the ones that come from Tula. The art of capsule making requires that "old world" craftsmanship, apparently. :-)
 
It could also be dirt on the contacts. That was/ is a problem some folks have with Schoeps mics. Anything out of whack at that point in the chain will cause problems.
 
Throwback said:
... but have been surprised by the additional self noise introduced by the low-cut pad included.
Click to expand...

I've not had the time to really setup and analyze my Oktava to this level due to taking a college course that sucks up all my 'free' time... but what is the setup you used to measure 'self-noise', as in what you used to capture the audio, and software to analyze (unless it was just 'listening' via your output (and what was the output if so...)).

I'll be trying to go through some of the test setups I've seen people mention this summer...
 
Thanks for the input

Thanks for the input

Scott - many thanks: yes the MM-1 is like the Mixpre-D in that it has low-cut filters (80 and 160 hz in front of the electronic amplification stage), so is a workable alternative, although, obviously, getting low-cut immediately after the capsule but before the MK-012's own preamp should be better (as indeed SD recommend). Richard and Rick - thanks for ideas: yes will clean things up (though there are very few parts) as a starting point and then replace the resistor and the capacitor: I have the values already, so its just a question of choosing what type - unless anyone chips in with advice to the contrary I'll probably go for polypropylene capacitor. Being in the UK, sending the capsule off to one of the places you recommend is probably a bit of a palaver, and I am confident with a soldering iron: it's not that fiddly a job. The mic itself is no noisier than expected, and certainly consistent with the 18db spec (its about the same as an NTG1 or NTG2) and price. Thanks for all your input - cheers, Roland
 
Throwback said:
...thanks for ideas: yes will clean things up (though there are very few parts)
Click to expand...
But it doesn't matter even if there were NO parts. The problem with leakage is the insulators (the plastic parts in the center.)
Although, indeed there may also be a leakage problem with the parts themselves (contamination on the outside surface of the resistor and/or capacitor.)

Mr. Joly (or some other Oktava or other condenser mic internals expert) may be able to identify what the recommended resistor and capacitor is if you want to DIY.
If you replace the parts yourself, remember that it is critical to use parts that are proven to be low-noise in high-impedance circuits.
I suspect that the people who source parts for Oktava either don't know, don't care, or can't afford the quality that would ensure low-noise products.
And remember that the outside surface of the components are leakage paths, also. So they must be thoroughly cleaned and not touched with your fingers.

Agreed that shipping the pad across the pond for repair seems excessive for such a simple fix.
 
Last edited:
Hi j1clark: I haven't measured self-noise in any scientific way, but just using my ears it is so very obviously noisy when the low-cut filter is added and all other settings (and normal settings too, for that - not crazy - 36 db gain) remain the same on my Sound Devices preamp. Cheers, Roland
 
Richard: thanks take the point about cleaning however simple the pad and, yes, will make contact with one of the Oktava experts as you recommend on the resistor and capacitor types for my DIY fix. Cheers, Roland
 
Thanks for the link Rick: sorry to be slow replying, but I've been sailing for a week w/o internet etc. (bliss). R
 
Just to say that I heard back from Bill Sitler, who confirmed that white noise is inherent in the Oktava MK012 low cut filter, that there is no mod, and, for this reason, he doesn't stock them. This also ties in with another email that I have just received from Oktava-online in Stuttgart saying that they have tried different components in the filter and that the noise stays. So the solution is to use the low-cut filter on your preamp (which at least on the SD preamps - and I assume any other decent equivalent - is before any amplification) and forget using the low-cut filter included in the 'movie-set' version (unless, of course, what you are recording is so loud that the self-noise of the Oktava filter doesn't matter). Cheers, Roland.
 
You must log in or register to reply here.
Back
Top