Octava MK/MC 319 Mods

omtayslick · #1 09-11-2004

Does anyone have any info on mods for this mic? Anyone done it? If so, what do you think?

MichaelJoly · #2 09-11-2004

There has been some discussion around this on rec.audio.pro (use Google groups, search "oktava mods") and over at TapeOp.com

Here's a cut and paste of post I made over there...

There just hasn't been a real cookbook-style article with good photos written about Oktava mods. There are a few folks around who have a jones for working on these things, and have described the process, but their posts are scattered hither and yon across the neet. Its freak'n irrrational this obsession about mod'n Oktavas is.

I would say be prepared to wreck one on the way to improving the others. But that's a cheap education in large diaphragm condensors right? I didn't really venture into mic modding till I had enough of them that I could overcome the fear of damaging one. And, being relaxed, confident and sober are all important aspects when you're working around thin diaphragms that don't take well to screwdriver slips.

A point I can make about the head grill mod - if you decide to do this (cut out the "fins" on the '219 and remove one layer of mesh screening) you will need to re-establish ground between the back half screen and the circuit board because removing the screening from the case breaks the ground connection. If you don't, it will hum like a bastard because the sheild is not catching and grounding 60Hz (50Hz for our Euro friends) being radiated by the wiring in your house or studio. This means you have to solder a small wire from the back screen, file a small notch in the PC board holder and run the wire to the PC board ground.

I've posted frequency vs amplitude specs for the "HF Boost Disc" found on the '219 and '319 over at rec.audio.pro. Again, Google groups is your friend. Removing this disc is a really easy, but delicate, way to improve transient response and high end detail on these mics. It seems counter intuitive to remove a high frequency lift device in order to gain better high end detail, but we're talking about time domain, not frequency domain effects. The stock mechanical HF boost filter on the large diaphragm Oktavas smear high end transient detail. Take them off, and you'll hear even more smooth. slightly rolled-off, but detailed high end these mics are known for.

The next mod that's essential for really being able to hear what a unique capsule the '219/'319 has is to dampen the body resonances. Just think: mass, and pressure. You'll need a combination of both to dampen the wicked singing of the bitch'n Oktava bodies. Treatments vary. Dense adhesive foam applied to both halves of the '219 case, liquid silicon goop poured into the bodies, adhesive-backed "limp mass" strips - sort of like roofing tar with lead foil attach. You get the idea - add some mass and pressure to absorb and dampen the ringing of the case.

The head grill of the ML-52-02 does not stop ringing no matter what you might do to it. I've heard it said that there is something about the molecular structure of the shit they use to cast those cases that is unstable. I'm not a metalurgist, but its a great story. If you've got an ML-52 you owe it to yourself to take the entire head grille assembly off. You do know you don't need it for RF reasons right? Yep, ribbons are low impedance devices and would be happy just sitting out in the open if they could be assured they wouldn't have their ribbons blown out of their brains by little breazes. You can always roll a single layer of window screen in the shape of an Oktava ML-16 and use a pop filter out front. But...dont you really want to return to distant talent-to-mic spacing and pick up some room sound for free?

Like what the other modders have said about the ML-52 - change the transformer to the Lundahl. And...change the skimpy little wires that lead from the ribbon terminal block to the transformer to some big heavy copper - gotta keep resistance low low low in a low impedance circuit.

How bout stickin a 5840 miniature pentode tube in an MC-012? Its been done. You could do it too.

0h, yeah...what they said about 1GOhm Rs in the head amp and upgrading to polypro coupling caps. But, check it out, rec.audio.pro guru Scott Dorsey says the '219/'319 transformer is actually pretty decent so don't need to change that in those mics.

Are these mic a terrific buy straight from Guitar Center to your home or studio? You bet.

Do you change strings on your guitar to suit your needs? Probably. Why not treat microphones the same way?

best to all, MJ

demto · #3 10-11-2004

I have trolled through the net and cant seem to locate all articles on MK319
mods, but here is what I have managed to find.

1. Remove the HF boost discs.
2 Stick felt to the diaphram side of the plastic seperator which seperates
the diaphram area and the electronics area.
3 Change the existing 510meg resitors to 1gb resistors.
4 Upgrade the diaphram coupling cap to silver mica or polystyrene.
5 There are 3 x 1uf electolyctic caps in the electronics circuit board.
apparently one of these needs to be changed for a better type. I am
going to change all three fo 1uf 63v polyester.
6 To be honest I am going to change as many of the remainining components
as I can for better where possible. I believe it cant do any harm even if
it doesnt do any extra good.

The order of importance seems to be 1,5,3,4,2

As yet I havnt done any of these mods as I am still obtaining the parts
I will need. When I have done this I will give it a go. Lets hope for the best.

I also have a question on this mike.
The parts list in the manual calls for 2 X 68pf caps but 680pf caps are
fitted. The caps are marked 680pf and I have checked them by
measurement. Can anybody confirm whether this is an error in the manual
or error in the parts fitted at the factory.

paddyponchero · #4 10-11-2004

Quote:

Originally Posted by demto

I have trolled through the net and cant seem to locate all articles on MK319
mods, but here is what I have managed to find.

1. Remove the HF boost discs.
2 Stick felt to the diaphram side of the plastic seperator which seperates
the diaphram area and the electronics area.
3 Change the existing 510meg resitors to 1gb resistors.
4 Upgrade the diaphram coupling cap to silver mica or polystyrene.
5 There are 3 x 1uf electolyctic caps in the electronics circuit board.
apparently one of these needs to be changed for a better type. I am
going to change all three fo 1uf 63v polyester.
6 To be honest I am going to change as many of the remainining components
as I can for better where possible. I believe it cant do any harm even if
it doesnt do any extra good.

The order of importance seems to be 1,5,3,4,2

As yet I havnt done any of these mods as I am still obtaining the parts
I will need. When I have done this I will give it a go. Lets hope for the best.

I also have a question on this mike.
The parts list in the manual calls for 2 X 68pf caps but 680pf caps are
fitted. The caps are marked 680pf and I have checked them by
measurement. Can anybody confirm whether this is an error in the manual
or error in the parts fitted at the factory.

I don't have a schematic for the mic but I'm guessing the 68/680pf caps are for RF filtering - I'd be happier with the larger value.

demto · #5 10-11-2004

thanks paddyponchero you may well be right. I just dont know.

I'm going to keep the caps at 680pf unless I definately hear otherwise.

Flatpicker · #6 10-11-2004

Quote:

Originally Posted by demto

I'm going to keep the caps at 680pf unless I definately hear otherwise.

1000pF polystyrenes from Mouser. There, you heard otherwise...

Flatpicker · #7 10-11-2004

BTW, the MK319 is the strangest condenser mic I’ve ever worked on. I worked on a couple – one sounded better with the disk on and the other with it off.

I changed/upgraded caps, transistors, and resistors, but I really can’t say that it sounds better. Different, for sure, but not necessarily better. I changed components out so many times, I wore the screws out from removing them and replacing them so often! I’m not finished, for I have a few things left to try. I just had to move on for now.

I'm not setting my hopes too high, though. I'm begining to think that the capsule isn't all that great to begin with and you know what they say about polishing a turd.

It was a good mic for the money back when GC sold them cheap, but definately not worth over $75-$100, IMHO.

reshp1 · #8 10-12-2004

How easy is it (if even possible) to take that disc on and off. I'd like to try it just for shits and giggles, but only if I can put it back the way it was if I don't like it.

Flatpicker · #9 10-12-2004

You just take a screw driver, remove the screws holding the disk, take it off and put the screws back. Hard part is not letting the screwdriver slip and poke a hole in the diaphragm. Do that and the mic becomes a paperweight.

reshp1 · #10 10-12-2004

Quote:

Originally Posted by Flatpicker

You just take a screw driver, remove the screws holding the disk, take it off and put the screws back. Hard part is not letting the screwdriver slip and poke a hole in the diaphragm. Do that and the mic becomes a paperweight.

Cool, thanks a lot. Sounds like something I can manage. I have access to an electronics lab at work and we've got a couple of fixtures that are good for really delicate tasks like this.

demto · #11 10-12-2004

Flatpicker, thank you for helping me with my question, I am gratefull for your
info and will get 1000pf polystyrenes

I have another couple of questions about modding this mic. can anybody
out there help?.

1. I am going to change the 510meg resistors to 1 gig. Do they have to be
anything special as to specification ie very low noise, ppm coeficient etc
or will a 'stock' resistor be OK. I can get a 'stock' resistor without any
problems but getting a 'super 1% 20ppm' etc will be more difficult here
in the UK.

2. Resistor R8 should be 1.8k ohm according to the manual. My R8 is marked
and measures 1k ohm. I cant work out if its been fitted by mistake, or
'selected' for some other reason. The manual mentions something about
'1k to 2.7k' but its in Russian and I dont understand.

Any help on any of the questions would be appreciated.

Flatpicker · #12 10-12-2004

Oktava MK319 Schmatic

The 1gigs (R1 and R2) can be 10% and you won't hear the difference - get the cheapest ones you can find.

R7 and R8 should probably be the same. Are you measuring them with one side lifted up out of the circuit? They won't measure correctly unless you take at least one side out.

reshp1 · #13 10-12-2004

Quote:

Originally Posted by Flatpicker

Oktava MK319 Schmatic

The 1gigs (R1 and R2) can be 10% and you won't hear the difference - get the cheapest ones you can find.

R7 and R8 should probably be the same. Are you measuring them with one side lifted up out of the circuit? They won't measure correctly unless you take at least one side out.

Yup, if 518 Meg works, then so will .8 to 1.2Gig

If you have the resistor (R1) in parallel with something (let say R2), the measurement will be R1*R2/(R1+R2) if you don't take it out of the circuit.

demto · #14 10-13-2004

To Flatpicker and Reshp1. Thanks for your replies.

I can get 'stock' 1gig resistors no problem. The 'stock' ones are 5%. I think
they are reasonably low noise as well. I just wondered whether they needed
to be 'ultra low noise' or any other special needs??.

I measured resistor R8 after it was completely removed from the circuit
board. Its marked and measures 1K although the manual calls for 1.8K
There is a footnote in Russian in the manual regarding this resistor which
I cant understand. Part of the foonote reads '1K.......2.7K'

1. Could be the factory fitted the wrong resistor.
2. Could be saying ' any value between 1K and 2.7K' will be alright.
3. Could be saying 'select resistor for best mic frequency response'.

Could be saying, could be saying,could be saying etc,etc.who knows.

Anyway, as the manual calls for 1.8K I am inclined to fit a 1.8K
What would you do, apart from jumping up and down on the mike'.Any
thoughts you have would be greatly appreciated.

Flatpicker · #15 10-13-2004

Quote:

Originally Posted by demto

I can get 'stock' 1gig resistors no problem. The 'stock' ones are 5%. I think they are reasonably low noise as well. I just wondered whether they needed to be 'ultra low noise' or any other special needs??....

5% is fine. The only time you need to worry about resistor noise is when using carbon comps in high voltage circuits. In low voltage circuits like this, resistor noise is not an issue.

Quote:

Originally Posted by demto

Anyway, as the manual calls for 1.8K I am inclined to fit a 1.8K...

What is the value of R7?

demto · #16 10-14-2004

To Flatpicker

My R7 is marked and measures 1.8K when disconnected from the circuit
board. The manual calls for 1.8K.

There is a similar footnote in the manual regarding R7 as there was for R8
except this time the figures mentioned are '1.5K.....1.8K'

Confusing. isn't it.

demto · #17 10-14-2004

Following on from resistor values that seem to vary from the value in the
manual I have now started to change the capacitors for better quality ones.

Each time I remove a component I measure it to see how it compares with
the values specified in the manual. I remove parts one at a time, measure
them, check to make sure the replacement measures OK and then fit it. By
doing things this way I hope not to make mistakes.
I dont gut out the complete board and hope I can remember which part goes
where.

Now this the problem, and I just wonder if it in any way it has some
connection with the fact that many people complain that the MK319
sound quality varies from one MK319 to another.

When I started to replace the caps this is what I found.

C5 has been fitted at the factory where C6 should be. C6 is fitted where
C5 should be. I'm not sure the values are correct either, they actually
measure 680PF and 270PF respectivly.

C4 has no markings. It measures 6.8NF which doesn't tie in with the
manual as far as I can see.

Has anybody else had simular problems ?

Its all very strange. My manual is also very poorly printed and I cant make
out the specs clearly.

Has anybody out there actually got or can suggest the correct values of the
following caps. C1 C2 C4 C5 C6

Any help would be appreciated.

crazydoc · #18 10-14-2004

Check out this thread at "The Lab" for some discussion of resistor values toward the end:
http://www.prodigy-pro.com/forum/viewtopic.php?t=487

If you can scan the footnotes in your manual and attach them here, Marik reads Russian and could translate.

demto · #19 10-14-2004

To Crazydoc

Thanks for your offer but I cant seem to attach the JPEG. I dont really
know much about computers.

The thread you sent me was great.

Bob's Mods · #20 10-14-2004

I basically swapped out all the lower quality caps for higher quality ones everywhere I could and I think I added .1 uF polypropylene cascaded (shunt) caps on the electrolytics. I left all values stock.
I also ripped out the inner screen which was easy. Gives the mic a more open sound.
All this gave it a nice performance boost. It's no U47 but who cares. It's just another color on the cheap.
I like it for acoustic. Sounds better than my buddy's stock MC012 when I A/B'd them.

Bob

maestro_dmc · #21 10-14-2004

Quote:

Originally Posted by demto

The parts list in the manual calls for 2 X 68pf caps but 680pf caps are
fitted.

You got a Manual?!

I didn't get a manual. I picked up two of the 319's at G.C. All I got was a lousy soft case and a ring style mic holder.

'Course I only paid $50 bucks each for the mics, so I really shouldn't complain.

demto · #22 10-14-2004

To Maestro

Life is not fair, it.

Some are born with Manuals. Some achieve Manuals. Others have Manuals
thrust upon them.

I had a Manual thrust upon me when I bought the mike.

Bearing in mind that I paid the equivalent of $350 when I bought it a few
years ago its the least they could do. Most things in the UK are VERY
expensive compared with the USA.

Go to the link Crazydoc mentions in his post. You will see a excellent wiring
diagram which was posted by Flatpicker. Thank god for Flatpicker I say.

Flatpicker · #23 10-14-2004

Quote:

Originally Posted by demto

Go to the link Crazydoc mentions in his post. You will see a excellent wiring diagram which was posted by Flatpicker. Thank god for Flatpicker I say.

Uhh..... Ok..... You're welcome!

And thank you, crazydoc, for posting the link.

(Actually, I posted a link to the same diagram a few post up.)

Flatpicker · #24 10-14-2004

Quote:

Originally Posted by Bob's Mods

I basically swapped out all the lower quality caps for higher quality ones everywhere I could and I think I added .1 uF polypropylene cascaded (shunt) caps on the electrolytics...Bob

C8 is the only ele directly in the signal's path so I just swapped it out with a 3.3uF metal film. Bypassing C3 with a .1uF might help too. Haven't tried that yet...

Quote:

Originally Posted by Bob's Mods

I also ripped out the inner screen which was easy. Gives the mic a more open sound...

Haven't tried that yet either, but I'm sure it helps. I wish I had time to mess with mine some more, but there's too many irons in the fire!

BTW, Bob, did you end up leaving the disk on or taking it off?

Bob's Mods · #25 10-14-2004

It's been some time since I fussed with that mic. I'm not recalling a "disk". Rattle my brain.