Oktava MK 219 mod parts layout
Old 15th March 2011
  #31
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Originally Posted by Haz-Mat-Strat View Post
These screws need to be put back in to the capsule. The capsule is lightly glued together and they are the only thing keeping the capsule secure. I cut them flush with a small wire cutter.

I prefer 470 to 1000pf Polystyrene over the Cog or Silver Mica capacitors for for the capsule to Fet coupling capacitor.

For those of you with MK319's, Marik's new transformer sounds great. It is bigger than the stock transformer, has a better sound, and takes transients better than the original. You need to cut the circuit board to fit the transformer in place. I have not tried to fit one into a 219. I will be getting another one shortly and I will see if it fits in the MK219.


The transformer has a center tap like the original and is compatible with the circuit setup.




Thanks Jim, I used the Dorsey 820 COG originally, but had some 1000pf polystyrene's (looks like a tiny version of the thing that they put in Neo's stomach in the Matrix right?) left over from doing some SDC mods so I've been playing. Being a first time circuit mod, I, and probably everyone else interested in the thread were or are scared to break something when doing the mod originally so you go with the Dorsey parts.

If you don't mind, what does the capacitance value generally do to the tone (for lack of better newbie words)? I'm hearing what seems to be a low end roll-off the lower the value. Am I just hearing things or on the right track?
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Old 15th March 2011
  #32
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I would have never thought that those screws would have cut so easily. This is actually a fragile mic the more I cut on it. I was able to cut the screws off with a very small pair of klein flush cut pliers.

Thanks Jim
Old 15th March 2011
  #33
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Quote:
Originally Posted by proletarian View Post
I would have never thought that those screws would have cut so easily. This is actually a fragile mic the more I cut on it. I was able to cut the screws off with a very small pair of klein flush cut pliers.



Be careful when you cut these screws, protect the capsule. Also when I take off the resonator disk, I cut the plastic disk so that the wire does not need to be re-soldered. Shorten the wire later.

Take the capsule off of the mount remove the mount, and put some heat shrink tubing on the aluminum mount. This can provide isolation for the capsule.

The RTV Silicone is a pain to work with. If you use it, you can smooth it with soapy water and your finger. I have found that a synthetic rubber coating called Plasti Dip provides better dampening, not as messy, dries faster and is somewhat self leveling. Use a large chop stick to apply it on the body.


Neumann used 470pf in their U87 and other mics. I think it is more of a "tone" difference than anything else. The higher capacitance seems to sound more open. The M Audio Sputnik mic has a very high capsule to Fet coupling cap, well over 2000pf. Some other mics use 1500pf. Conduct your own tests to find what value/type that you like.








Old 15th March 2011
  #34
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hi jim,

aren't c2 and r2 acting as a high pass filter?

i was guessing that increasing the value of c2 would lower the corner frequency and allow more bass through.

wouldn't any tonal changes be more a result of the type of capacitor used.

not sure so thought i'd ask.
Old 15th March 2011
  #35
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What happens if you loosen the screw at the center of the capsule? Is the mic ruined, or is it just risky to damage the diaphragm with the screwdriver? I don't see this mentioned in the articles.
Old 15th March 2011
  #36
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Quote:
Originally Posted by gouge View Post
hi jim,

aren't c2 and r2 acting as a high pass filter?

i was guessing that increasing the value of c2 would lower the corner frequency and allow more bass through.

wouldn't any tonal changes be more a result of the type of capacitor used.

not sure so thought i'd ask.

The primary function of C1 is to block the DC voltage to the input of the Fet. When you increase the size it becomes more linier.

The type of capacitor has more of an impact on the tone. However there are small tonal changes with different values.

Scott Dorsey
Recording Magazine Quote:
"R3 and R4 are a voltage-dividing ladder shunted between ground and the rail voltage. They are used to generate a fixed DC voltage to set the FET bias through R2, another very high-value resistor, so that the FET is just slightly turned on at all times with no signal in the mic."


Blewgrass
tutt Be careful not to over tighten the center screw tutt







Jim Jacobsen
JJ Audio
Old 15th March 2011
  #37
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Awesome info Jim! Thanks a ton for taking the time to offer the advice.
Old 15th March 2011
  #38
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Quote:
Originally Posted by Haz-Mat-Strat View Post

Blewgrass
tutt Be careful not to over tighten the center screw tutt







Jim Jacobsen
JJ Audio


Me no overtighten!

Awesome stuff... I second the thanks!
Old 18th March 2011
  #39
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Just finished partially modding my 219 and the results are great! (I did all the front end electronics, and c3, 7,8, and 9, the screen, removed diisks, and dampened body. I didn't mess with the low priority resistors and caps. At first I had some hideous noises but after cleaning some solder joints that were shorting I'm good! I thought I had pissed away a perfectly good mic but I stuck to my plan and it came out nice sounding

To other DIY people reading this I say with the utmost humility.... I suck at this!... No I mean really suck! So... what I'm saying here, is if I can get a good mic out of this .... YOU CAN!

Peace

Steve
Old 20th March 2011
  #40
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I had created a thread documenting my progress on the MK-219 mods. If you searched for them on here, you probably already read what I had to say about it.

I took a cheater path, of a sort, since I bought the mod kit from Bill Sitler. It works very well and I have done the same mod to three MK-219 mics now. I am very pleased with the results. I find the microphones are very useful tools for the studio. At some point I plan to buy a fourth and mod it so I have a full set... of four! I just happened to have a case and foam that perfectly fits four MK-219 microphones, so on my C or D list of purchases, a fourth MK-219 to fill the empty slot in my case burns for my future attention.

Anyway, if you want a quick path to some wonderful MK-219 results, check out the Bill Sitler mod kit: Oktava MK-219 Modification Kits and Service I know if you sourced parts out, you could in theory do this for less $$$, but then what parts would you buy? And you would buy 100 resistors when you need one, or ten caps when you only needed one and so on. So in that regard, the kit does offer some value. Also it could provide a person a starting point to maybe try swapping out some values for various caps for changing the sound if one were so inclined.

I did NOT really get into trying to bias the FET. Should I? I do not know. All three of my kit mods sound the same to my ears, and they sound good. Hmmm, maybe they could sound better, but I am not missing it.

In case you have an interest in checking out the thread I posted on the 219 mods I did, check it out: Oktava MK219 stock versus mod head basket versus mod electronics

On my post, I did not put up any photos. I started out taking pictures, but ultimately decided they did not reveal as much as I hoped they would compared with the text. I say that as a person who makes his living as a photographer, by the way.

Anyhow, I could not recommend the mods more. This is a worthy effort with fantastic results.
Old 8th May 2011
  #41
ico
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"680pF 100volts C0G 810-FK28C0G2A681J
1500pF 100volts C0G 810-FK24C0G2A152J
820pF 100volts C0G 810-FK18C0G2A821J


sorry to resurrect this thread, but i have seen you purchased three different values for the capsule -fet coupling cap...
i just wandered if you swapped those end can refer your preferences.....
thanks!
Old 18th November 2012
  #42
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I have successfully completed 219 mod following Dorsey's article.
I have recorded dozen of different instruments in studio side by side with stock 219. Stock sounds a bit harsh and mid-rangey, the only difference I have noticed, considering I was listening to a bunch of different instruments. Mod sounds a bit more open, not harsh and it seems that bottom end is punchier but it's extremely subtle. Definitely, this modded microphone has a warm vibe to it. Doesn't sound good on everything but it could be useful on some sources. I liked it on acoustic guitar a lot, not much on classical.
On accordion sounds nice. I wasn't impressed how it sounded on flutes. Banjo sound was all right, nothing special. Darbuka was also dull, actually the stock 219 won on this darbuka.

overall I think modded 219 could be very useful color mic to your cabinet.

Anyone care to hear the examples
Old 15th March 2013
  #43
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Proletarian, THANK YOU for such a great great post! This has been super useful for those of us climbing up the tech ladder. I've got a good voice but this mod has been so useful to me just with the physical modifications so far. I'm looking forward to trying to put some of the new electronic components in and trying this out.

Keep it coming.

I'll have more questions regarding this and I think I'll post photos of my mic's board to see which one I have...maybe board 2...

Cheers,
BW
Old 9th May 2013
  #44
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Fet bias

Any good article on how to set bias properly on 2SK170BL?
Old 26th May 2013
  #45
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Thank you Proletarian! this is super helpful. I've just only done the mechanical mods and it has made a huge improvement.

However, I think I messed something up. When I replaced the mesh with a single layer, I took care to ground the mesh to the body with wire glue (a tip I red on another forum to prevent 50 cycle hum). But when I put the mic back together it had the hum. I know it has to be something with the head basket because when I put my hand close to the mesh, the hum gets louder. and it goes away when I touch it. Could it be a bad connection with the wire glue? I covered quite a bit of surface with it. Should I have scoured the surface of the body?

I would greatly appreciate any advice
Old 27th May 2013
  #46
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Quote:
Originally Posted by rpagala View Post
I removed inner basket and cut out front and back grill, epoxied the screen with 2 parts conductive epoxy and made sure the shim/clip are installed on the bottom so the 2 halves have a good contact with the ground otherwise it will hum like a b*tch...

I've been tinkering with my MK219 for a while now and I noticed a big difference is changing the C8 (Cornell Dublier 150) and C2. Anyway a quick recording.... 12 yrs old playing ukelele, dry recording with light compression with only one mic. Let me know what you think..
Try to solder a piece of hookup wire from the mesh to mic body...
Old 27th May 2013
  #47
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Quote:
Originally Posted by Nate O View Post
Thank you Proletarian! this is super helpful. I've just only done the mechanical mods and it has made a huge improvement.

However, I think I messed something up. When I replaced the mesh with a single layer, I took care to ground the mesh to the body with wire glue (a tip I red on another forum to prevent 50 cycle hum). But when I put the mic back together it had the hum. I know it has to be something with the head basket because when I put my hand close to the mesh, the hum gets louder. and it goes away when I touch it. Could it be a bad connection with the wire glue? I covered quite a bit of surface with it. Should I have scoured the surface of the body?

I would greatly appreciate any advice
Did you get both the little copper pieces---the curved ones that wrap around the XLR jack and are sandwiched between the body halves---back in place properly? If you do not do that, the mic will buzzzzzzzzzzzzzzzzzzz. Likewise, if the screen/ mesh is not touching the aluminum body very well, you'll compromise your faraday cage and you'll get the same sort of buzz. So it could be a couple things. Or if the ground wire connection to pin one was at some point broken or not connected very well... buzz.
Old 27th May 2013
  #48
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Quote:
Originally Posted by Puffer Fish View Post
Did you get both the little copper pieces---the curved ones that wrap around the XLR jack and are sandwiched between the body halves---back in place properly? If you do not do that, the mic will buzzzzzzzzzzzzzzzzzzz. Likewise, if the screen/ mesh is not touching the aluminum body very well, you'll compromise your faraday cage and you'll get the same sort of buzz. So it could be a couple things. Or if the ground wire connection to pin one was at some point broken or not connected very well... buzz.
when I took the mic apart I believe there was only a copper piece on one side, which I replaced. The wire to ground looks like it's got a solid connection. I think I'll try soldering a wire from the mesh to the body. Should I do this to both sides of the body? And do the two halves of the mesh need to have an electrical connection?
Old 27th May 2013
  #49
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a connection with each other I mean
Old 27th May 2013
  #50
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Quote:
Originally Posted by Nate O View Post
when I took the mic apart I believe there was only a copper piece on one side, which I replaced. The wire to ground looks like it's got a solid connection. I think I'll try soldering a wire from the mesh to the body. Should I do this to both sides of the body? And do the two halves of the mesh need to have an electrical connection?
I had the same problem the other day and what I did was I took my dremel and exposed the metal next to the grill and applied a conductive epoxy and I made sure the copper strip were tight when I put the 2 halves together, I had to bend them a little to make tight fit. After all that the hum went away....
Old 28th May 2013
  #51
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Quote:
Originally Posted by Nate O View Post
when I took the mic apart I believe there was only a copper piece on one side, which I replaced.
There is supposed to be TWO of those little curved copper tabs: one for each half of the mic body. They connect the ground from the XLR jack to the mic body, which in turn connects the ground to the wire mesh surrounding the capsule, which in turn creates the Faraday cage thus completing the ground for the microphone and thus eliminating that irritating hum.

Yes, you need two of them. A piece of bare copper wire that would make a snug fit would accomplish the same task. Fix that and I bet you'll be back in business.
Old 28th May 2013
  #52
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thanks for all the replies guys. I found another piece of copper to bridge the other side of the body. I also ran a bead of solder across the bottom of the mesh where it meets the body. Just put it back together and I'm still getting hum. When I touch the mesh with my hand, the hum goes away. What could I be missing here?
Old 29th May 2013
  #53
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Hmmm.... look for ground wire traces and make sure they are all soldered properly. Make absolutely certain those little copper tabs are fitted in their respective spots snug between the mic body halves and the XLR jack. Look more closely at the mesh---did you drop in new mesh or did you use the stuff that came with the mic?

I simply used the wire mesh that came with the mics. I did indeed remove it from the body when I nipped away the metal bars that make up the grill and then filed down the barbs from the effort. I simply hot-glued the mesh back in place, so it strikes me as odd that you are having problems with the ground in regards to the mesh. I did this to three MK-219, no problems. I doubt the the mesh on my three mics is doing very much by way of isolating or rather shielding the mic capsule. The body certainly is, though, so I suspect you have a loose ground or that those frustrating little copper tabs did not seat into place very well. They are a silly part of the mic design, for sure.
Old 30th May 2013
  #54
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i think i've narrowed my problem down to radio interference. I've got one more thing to try in terms of getting rid of the hum. I read somewhere that it was 50 cycle hum, but i have determined that it is 60hz. maybe because im in the U.S. I'm surprised more people haven't had this issue when replacing the mesh with a single layer, because grounding it to the body did not take care of it for me.
Old 5th June 2013
  #55
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well I took my mk219 to an electronics guy, supposedly the premier "mad scientist" in town, and he said my problem was very complex and I had bit off more than I could handle. The problem is obviously not radio interference, which I learned today spans from 3kHz to 300GHz.

Can you guys who have done the mod please do me a favor so I know I'm not chasing my tail?

Power up your mk219, cut everything above 100Hz out of your monitor send, and turn it up. Listen for the hum and see if it goes away when you touch the mesh.

thanks in advance
Old 5th June 2013
  #56
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I do not have the time or the opportunity to do that for you, I am sorry. I am in the middle of relocating and will not have access to my studio anymore.

Do you have the Dorsey mod article? If not, let me know and I might be able to find it for you in my private archive.

Do you have the 219 schematic? If not, I know I have that. I am sorry, but I think you are going to have to work through this on your own. There is only so much anyone can do for you via correspondence like this. Or at least, there is only so much I can do, anyway.

Maybe someone else can do what you ask. But to be fair, I am not sure what you are looking for here. I do not have the hum issue you are describing, so turning my mic amp up and touching the mesh of any of my 219s will not yield any results. What you describe seems like a loose (cold solder joint?) or broken or missing ground to me.

Try this: take your mic body apart again and then plug the mic into your preamp and listen for the buzz/ hum. Is it worse now? It SHOULD be as the ground is all kinds of broken at that point. If the buzz is the same, then the body is not connecting the ground. That's one thing you could check out.

And another suggestions: Try hooking up your mic and listen to the hum/ buzz and run a wire to the body and send it to earth/ ground someplace. That is, attach a wire to open metal on the mic body somehow, in such a way as you know it is making good contact to the bare metal--the mesh might be a good choice. Touch the other end of that wire to a grounding source. The hum should go away, again proving that the issue is a ground issue.

Good luck.
Old 7th June 2013
  #57
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Quote:
Originally Posted by Nate O View Post
Thank you Proletarian! this is super helpful. I've just only done the mechanical mods and it has made a huge improvement.

However, I think I messed something up. When I replaced the mesh with a single layer, I took care to ground the mesh to the body with wire glue (a tip I red on another forum to prevent 50 cycle hum). But when I put the mic back together it had the hum. I know it has to be something with the head basket because when I put my hand close to the mesh, the hum gets louder. and it goes away when I touch it. Could it be a bad connection with the wire glue? I covered quite a bit of surface with it. Should I have scoured the surface of the body?

I would greatly appreciate any advice
Hi Nate,

Is the mesh that you glued into the mic the stock mesh or something else?

I always dremel the inside of the body where the mesh sits and then use a Silver bearing Epoxy.










Jim Jacobsen
JJ Audio
.
Old 8th June 2013
  #58
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Hey Jim,

Yes, I glued in one layer of the stock mesh. I scoured the surface of the body with a file, and I laid a bead of solder across most of the bottom contact on both sides of the body. I also re-soldered all the ground traces. I'd like to be able to fix it, but I may just have to send it in.

Thanks

Thank you Puffer Fish as well
Old 8th June 2013
  #59
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What kind of glue did you use? I use a very expensive Silver Bearing solder. $40.00 for 2 small tubes.

Solder does not work very well on the 219 body.







Jim Jacobsen
JJ Audio




.
Old 9th June 2013
  #60
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Quote:
Originally Posted by Haz-Mat-Strat View Post
Solder does not work very well on the 219 body.
That has been my experience as well, although Jim no doubt has spent way more time with this mic body than I have. I think the body is made from cast aluminum, so good luck making the solder stick. I suspect that is why the Oktava folks opted to use those little copper tabs sandwiched in between the mic body halves and the XLR connector to complete the ground---soldering would not work or likely broke away from any body connections.

Is there a glue that conducts electricity? If so, then that would seem like a good choice for reconnecting the mesh to the mic body.
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