Why Are people using the 2sk170BL to upgrade the Oktava 319??

[Paul678]

I've done some work on Oktavas and even wrote a modding article for Sound & Recording Magazine, Germany. Personally, I think MK-219s benefit from removing the outer parts of the grille a lot. Removing the HF resonators is a matter of taste and depends on the sound of the individual capsule. I left it on most of my MK-219s and all of both of my MK-319s. Changed no FETs but did some cap changes (that said, the original caps have a sound of their own). Removing the switches (which create parasitic capacitance in the high impedance parts) helps, too. In the MK-319 you can implement a different switching scheme in the lower impedance part that does not compromise the performance; in the MK-219 there's not enough room for that. I later changed one of my MK-319 to a self-designed tube circuit and developed some more mods that I prefer to keep to myself for the time being. You can have a lot of modding fun with those mics.

Or buy a MK-101 which IMO sounds fine stock.

Ok, the resonator disks are definitely needed in my particular unit, so I'm leaving them
in. 

I also removed the daughter board for the switches, but if I ever record something
really loud (like saxophone) , the -10dB switch might be useful.    Can you recommend a
different switching scheme in the lower impedance part of the circuit that does not
compromise the performance?

Thanks.

I also removed one layer of mesh, and replaced C2 with a 1000pF polypropylene, and
this is an awesome used mic for $86!  Sounds great for my acoustic guitar......

 

[Gus]

Paul678

Why did you remove a layer of mesh? something you read on the web? 
Question things about microphones you read on the web.  I think removing mesh can be a mistake.  Besides RF interference.

 

[Paul678]

Paul678

Why did you remove a layer of mesh? something you read on the web? 
Question things about microphones you read on the web.  I think removing mesh can be a mistake.  Besides RF interference.

That's a pretty accepted portion of the mods.  I haven't heard anyone complain about
removing a mesh layer, and mine sounds better after doing that and the other mods I mentioned.

Still, I'm keeping ALL the parts I removed, just in case I decide to put them back, like the
resonator disks.  It might be tricky to replace the mesh, but I'm sure it can be done.

I still need a circuit for a -10dB switch that is in the lower impedance area of the mic.....

 

[Rossi]

In some instances removing some mesh can help, but keep in mind that you also remove protection for the capsule. Also keep in mind that most classic mics have two or three layer mesh baskets.

A better way to implement a pad in the MK-319 is to reduce the capsule polarization. Half the voltage is -6 dB; 1/4 thus is -12 dB. I'm not going to draw a schematic, but it's fairly easy to implement a switchable voltage divider.

 

[Gus]

I don't think most people are going change something on a microphone and report back it did not work well.
Who says it is an accepted portion of the mod? 
FWIW I even left the bars at the grill alone in my two 219s.
IIRC I have posted about removing the inner mesh of a MXLV67 and it made things worse.
Also think about if the mesh is not needed why do the companies use it?  it cost money.

Paul678

Why did you remove a layer of mesh? something you read on the web? 
Question things about microphones you read on the web.  I think removing mesh can be a mistake.  Besides RF interference.

That's a pretty accepted portion of the mods.  I haven't heard anyone complain about
removing a mesh layer, and mine sounds better after doing that and the other mods I mentioned.

 

[Paul678]

In some instances removing some mesh can help, but keep in mind that you also remove protection for the capsule. Also keep in mind that most classic mics have two or three layer mesh baskets.

A better way to implement a pad in the MK-319 is to reduce the capsule polarization. Half the voltage is -6 dB; 1/4 thus is -12 dB. I'm not going to draw a schematic, but it's fairly easy to implement a switchable voltage divider.

  Is it really as simple as 20*Log(v1/v2)?  The DC polarization voltage is linearly related to the RMS
signal AC voltage?

  It wouldn't surprise me if that's a simplification, but I'll go with it. 

  So I could put a simple voltage divider made up of two 100k ohm resistors between
C9 and R10, to retain the filtering of C9 (1uf).  Problem is, the magnetic-reed switches are
single pole- single pole, so I couldn't use them here, I'd have to go single pole-double throw.

 

[Rossi]

It's possible to do it with the original reed switches. Just connect/disconnect the lower resistor of the voltage divider. The capsule doesn't draw any current, so the upper resistor doesn't drop any voltage when disconnected from the lower resistor.

@ Gus: IMO it's definitely worth cutting the bars on the MK-219. They're just too close to the capsule. I compared and measured before and after the mod. The treble roll-off of the grille is definitely audible. Actually, Oktava may have introduced the HF-reflectors to remedy the effect of the grille - the two more or less cancel each other out. So there is a kind of logic in "pulling a Joly", i.e. removing both the grille bars and the disks. Also, the MK-219 looks more like a mic with the bars removed. ;D

Still, in most Oktavas I prefer the sound with the disks in place.

 

[Paul678]

I don't think most people are going change something on a microphone and report back it did not work well.
Who says it is an accepted portion of the mod? 
FWIW I even left the bars at the grill alone in my two 219s.
IIRC I have posted about removing the inner mesh of a MXLV67 and it made things worse.
Also think about if the mesh is not needed why do the companies use it?  it cost money.

Paul678

Why did you remove a layer of mesh? something you read on the web? 
Question things about microphones you read on the web.  I think removing mesh can be a mistake.  Besides RF interference.

That's a pretty accepted portion of the mods.  I haven't heard anyone complain about
removing a mesh layer, and mine sounds better after doing that and the other mods I mentioned.

    I just reported back that I didn't like my disks removed!    Thank God it's was simple to
put them back, but there's proof not every mod is a good one.  I depends on your taste.

    My mic sounds better with the inner mesh removed.

 

 

[Paul678]

It's possible to do it with the original reed switches. Just connect/disconnect the lower resistor of the voltage divider. The capsule doesn't draw any current, so the upper resistor doesn't drop any voltage when disconnected from the lower resistor.

Still, in most Oktavas I prefer the sound with the disks in place.

Ok, that sounds like a good idea.  Perhaps two 1 Meg resistors would be better?  Although it's 0.24 mA
for two 100k Ohm resistors, so it shouldn't matter. 

Yes, I prefer the disks in my 319.

 

[Paul678]

I just discussed this with Scott Dorsey, and basically
he said:

"Changing the polarization voltage won't change the output level in the
way you want, as the frequency response and linearity will change
also.  Adding a shunt capacitance will, but the quality of the
capacitor becomes a big issue and it never sounds as good anyway.
Remember the electrostatic attraction is where part of the capsule
tension comes from; change the voltage and you change the capsule tuning.

Also, of course, it doesn't really buy you all that much since the capsule
becomes nonlinear at levels not much higher than the electronics.

I would just stay away from it.  If you want to close-mike a horn, use an
re-20 or something that is appropriate for the job.  Buy some N/D 468s used
for that kind of thing; they are tight, not horrible off-axis, cheap, and
don't have a presence boost."

So I'm probably not going to add this pad back in, but I found some
2SK170BL FETs on Ebay.....

 

[Rossi]

The polarization voltage plays only a small part in the diaphragm tension. When you do comparative measurements within the usable range of voltages (as I have done), there's hardly any change in frequency response. Which would be the case if the capsule resonance was seriously altered. Of course you are likely to encounter changes near to the voltage when the capsule collapses. But that's well above the usable voltage range.

Pad implementation via polarization voltage is not my invention; it has been done in commercial microphones such as the TLM170. All known pad implementations are compromised in some way, but this one probably the least. One added benefit is that the capsule distortion is slightly reduced as the electrostatic attraction decreases. By comparison, a small cap in parallel with the capsule increases capsule distortion.

 

[EEMO1]

Paul678
Question things about microphones you read on the web.  I think removing mesh can be a mistake.  Besides RF interference.

tried it once. made the mic worse. not doing it again.