Oktava MKL2500 Mods

[lightandmind]

Total newbie here, what are some basic mods I can do to get more detail and sparkle out of this thing? Should I replace the caps in the PSU and the mic? With what? The heater in the P/S is on a regulator with a trim pot to adjust, I've heard that I should adjust it from 4.5v to around 5.4v, where can I put the lead of the multimeter to see what I'm getting? I'm thinking of swapping the stock tube in the mic itself out with a Mullard 6ak5, does that sound like a good idea? Thanks!

 

[zebra50]

Here was our discussion from 2004 (!)

http://www.groupdiy.com/index.php?topic=509.0

I have moved website since then, so the missing schematic are now at...

That is for early versions of that mic. Some later ones have a much more conventional design that is close to the MKL5000....

http://www.xaudia.com/xaudia/Schematics/Pages/Oktava_files/Media/MKL5000/MKL5000.jpg

Some internal shots are here...

http://www.xaudia.com/xaudia/Galleries/Pages/Oktava.html

Unfortunately my mic was stolen from the studio soon after, so I can't recall from this distance how it sounded. I did change the caps in the mic.

Stewart

 

[ArR]

I have no experience of the MKL2500 but plenty of bitter experience with the MKL5000.
The PSU looks like the same one.
Of the four PSU's I had, 3 added various amounts of hum.
You can see the wires from the mic connector to the PSU board are unscreened and (can, depending on how they bend) lie right next to the A.C. power.
Also have had problems with that earth lift switch deciding to give earth lift if you want it or not.
I removed the  switch and linked it out on the board.
Replaced the outgoing XLR with a chassis mount one so that the audio path can go directly from one connector to the other (screened).
Also shortened the High voltage and heater supply wires to keep them away from the A.C.
Changed the earth wires to all star from one point.
The result was a lot less hum.

The special quality (ie military) designations for the 6AK5 / EF95 valves are ...
M8100 and CV4010
I bought a handful of CV4010's and had no noisy ones, may have been just lucky though.

Here is a photo of before and after. (actually 2 different PSU's)

Not really an answer to your question, unless you have hum  ;-)

Simon

 

[lightandmind]

Thanks guys! Awesome pics and info Simon, (great for a newb such as I), thanks for the schematic and stuff too Stewart, you guys rawk!

 

[lightandmind]

So, should I possibly replace ALL the caps in the P/S AND mic in order to get it singing it's sweetest? I keep hearing about Black Gates caps, should I replace them all with those bad boys or what?

 

[Whoops]

Hello,
thank you so much for the info on the PSU mods, it makes a lot of sense to do those changes.

anyone has the schematic for this PSU?

Thank you so much

 

[Whoops]

Hi again,
I'm still trying to fix my MKL-5000 mic.

Does anyone have the schematic for the PSU?

Thank you so much