Oktava MKL 5000 heater voltage

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stefan

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Joined
Dec 5, 2004
Messages
121
Location
Sweden
I own two Oktava MKL 5000 mics and in the info Oktava calls the tube 6C15P. The PSU was factorytrimmed for 4,5V for the heaters. Is there anything to gain by raising the heaters to 5,4 or even 6,3? if the labeling is correct this would indicate that the tube should be used at 6,3V heater, Right? Since I don´t care much for theese mics I really think that almost any change in sound would be an improvement.
 
Yes it is rated 6V but able to pass 45mA. Since you are probably working more like 1mA, it is not necessary to put a full 6.3V heat on it. And noise may be lower at lower voltage.

The tube may run a wee bit better with more heat, if the power supply can stand the increased current, and if the increased heat inside the mike (about double) does not melt anything.
 
The MKL2500 I saw had 4.5V on the heater too. My perception was that it sounded a little better at a higher voltage (5-point-something). I didn't run into any trouble playing with the heater voltage but I didn't have the mic running for a very long time at higher voltage.

I'm guessing the 5000 is just a multi-pattern version of the 2500. Do a search here for the MKL2500 or check the microphone meta to track down the circuit and what the tube is really called in Russian letters. :grin:
 
[quote author="zebra50"]The MKL2500 I saw had 4.5V on the heater too. My perception was that it sounded a little better at a higher voltage (5-point-something). I didn't run into any trouble playing with the heater voltage but I didn't have the mic running for a very long time at higher voltage.

I'm guessing the 5000 is just a multi-pattern version of the 2500. Do a search here for the MKL2500 or check the microphone meta to track down the circuit and what the tube is really called in Russian letters. :grin:[/quote]

Ooop! wrong mic.. sorry I'm making a new post..

Hey guys I have two of those MKL2500s they were selling at GC and they
had a bad hum. I fixed the bad hum by soldering a jumper from the shield of the cable to the colar of 6 pin XLR at the mic end and it's "almost" gone. I'm still getting a tiny bit of hum. I noticed that pin 3 on the PS side doesn't connect to anything do you think I should jumper that to ground also ? Or is there anything else I should try ? I also have some 1g ohm resistors left over from my last head amp build and I was wondering if I should replace R1 with one of those, what should I expect to happen to the sound ?

This is what my mic looks like inside

http://webpages.charter.net/coffeys/mkl2500head.jpg

This is the PS I have..

http://webpages.charter.net/coffeys/mkl2500ps.jpg
 
stefan said:
I own two Oktava MKL 5000 mics and in the info Oktava calls the tube 6C15P.

just for future reference,

My Oktava MKL-5000 has a 6AK5 tube (says Made in USA) and not a 6C15P, so the original tube in my microphone was replaced for a 6AK5 at some point.
Other people seem to have 6AK5 also, I don't know if 6C15P was used or not in some versions

Also the Heater voltage in my PSU is also 4,5V and not 6,3V like the 6AK5 data sheet suggests.
Strange they decided to use a lower voltage
 
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