Do you hate the PCB in the MK012?

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Svart

Well-known member
Joined
Jun 4, 2004
Messages
5,134
Location
Atlanta GA USA
fear not, for I have recently took the initiative to draw up a replacement with some improvements(or not) stemming from my fight and subsequent loss with my MK-012s. Yes, the traces have started to come off and so forth.

http://www.geocities.com/noireclipse/mc012.pdf

I haven't etched one yet, but will this week unless anyone spots anything i need to fix.

Some notes..

The JFET footprint is DIFFERENT than the original, this one is for the 2SK170 series. I have also tried to include extra pads for ease of installation of resistors and such. the trace widths are a bit larger and should help keep the traces from coming off the board like they do with the original. I have not measured the lytic caps to see if they will fit yet so that might change soon.. The rest is pretty much the same and there are a few mm at the ends where the cutouts for wiring and the spring socket are. I haven't gotten around to laying those out yet but it shouldn't be too much trouble to cut them out to fit. I also included a boundary line around the board for the maximum size. cutting the board out slightly smaller than that line was the idea.

PM with questions or comments.

:thumb:
 
I have not traced what you designed.

What I would do is have the gate and input cap wired in the air or on teflon standoffs.

A mod I did to my square microphone is causing a noise problem because of leakage in a switch body.

leakage causes noise with microphone try to keep the gate and High Z ends of the input section off the PCB
 
ok, thanks, I actually didn't know that!

I just added a trace to it because the sk170's gate is the central pin, not the outer pin like the one i have. i thought it would be easier like this, but it still goes to a point where you could mount the standoffs no prob. the cap was still to be mounted on the backside like the original though.

:thumb:
 
if anyone was interested I will have a revised version of this up tommorrow. I have finished stuffing and building the pcb and will test this weekend.

:thumb:
 
ok updated! this removes the trace for the gate of the sk170 and adds the holes for the teflon posts and the edges of the PCB are now like the original. everything else fits fairly well. good luck!
 
for those of you following this, I tested the mics over the weekend with the new pcb, using sk170 FETs and all of the other dorsey mods. they sound great! PCBs fit well and haven't had any problems. happy DIY!
 
the improvements are mechanical only. those of us who have modded these mics already know the pain in the ass that these PCBs are.. heat them more than once and the trace comes right off. I have relaid the pcb with thicker traces and more through-hole pads for more possibility. i also used the pinout for the 2sk170 JFET instead of the one currently on the pcb since this is one of the main upgrades you can do.

electrical mods to this mic are outlined in the Dorsey mod, found easily in this forum, which boils down to switching out poor quality parts for good ones.

:thumb:
 
I got the Dorsey article and opened up one of my MK-012s, and really mine didn't have the same nasty parts as the Dorsey one. Plus the sound is really quite good already, so I haven't bothered going any further.

My Oktavas (they all sound the same) are all the ones in the little black plastic box marked "Microphone MK-012-01", and one of them even has a serial number.
 
[quote author="Scodiddly"]I got the Dorsey article and opened up one of my MK-012s, and really mine didn't have the same nasty parts as the Dorsey one. Plus the sound is really quite good already, so I haven't bothered going any further.

My Oktavas (they all sound the same) are all the ones in the little black plastic box marked "Microphone MK-012-01", and one of them even has a serial number.[/quote]

I'm in the same boat, except that my little boxes are gray. I opened up one of the mics and the parts already appear much nicer than the un-modded example. I haven't checked the other mic for component differences, which are I hear are common in these. I have done a null test, and the mics are nearly identical in sound.

Elsewhere someone stated that these mics don't provide a true balanced output. Any truth to that? It hasn't been an issue, so I suppose it doesn't much matter.
 
yes it's not a true balanced output, but it is impedence balanced.

my mics came with better parts than the dorsey example too, but upgrading to 1-2G Rs and better fet do improve this mic. my mic came with BC output caps stock so i did not upgrade those.
 
My two 012s have BC electros they seem to be fine.

I am curious if all the circuits are the same(not part numbers but part types) and if the circuits have the same IDSS fets and bias points.

The pnp transistor should not matter much with the white follower type circuit used in the 012.

The 012 not using a DC to DC converter looks to have the fet current set lower than the gefell transformerless schematic at gyraf. I guess to keep the capsule voltage up.

The link to Zebras site of the schematic of the 012 seems to be broken.

I kind of like this circuit.

Think LDC with a nice 2:1 output transformer.
 
Can someone please send me the PDF file for this layout?

I'm a latecomer to this thread and I'll like to try modding the MC012.

Thanks, Kato
 
Thanks, I appreciate it!

For other latecomers, the difficult to find transistor can be found in a pack of 10 here:

http://www.ampslab.com/trans_2sk170bl.htm
 
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