this line
Yes, you are right 
now i got it
another thing that I always do to avoid shifting things, I trace the +12 with red felt pen across the entire line of the stripboard, same in black for the GND and in blue for the -12
6 Likes
Looks like @Dud has already identified the issues, but I posted an annotated stripboard here, with the supply lines and voltages marked out:
(measure the voltages from ground to the pin, and make sure you have both the right voltages and the right polarity)
To find the supply pins more generally, use google to find the datasheet, locate the right pinout, and look for pins named VCC, VEE, or similar. For example, the TL074 datasheet is here and it has the following drawing:
Note the pins named VCC+ and VCC−; they’re the positive and the negative supply for this package. The negative supply is sometimes named VEE or VSS, and the positive supply can also have multiple names, and sometimes the chip wants a GND too; you may have to look at the pin descriptions to figure out what’s what. If you stumble upon some datasheet where it’s not clear, the people on this forum can help.
4 Likes
First Thx a lot, now I have some kind of filterng BUT the Diodes are alsways clipping I guess I have to change the Input resistor, right?
And if I unplug everything except the Output of the filter it sounds and beaves like an oscillator ?!??
@Dud I´ve looked over my PCB and the Schematic and i´ve don´t forgot a row.
Just the Cable were @ the wrong place and one Cable from the cutoff pot.
Checked also the cable at the switch and there okay too…
With a lot of resonance a VCF can enter in auto oscillation, like a VCO, it’s normal, try to put the resonance pot to zero
for the line, maybe i don’t see very well on your pic, and so much the better that i’m wrong it’s not the whole circuit to be redone 
i check again and if you look on schem (5 line between the 2 IC) and not a power wire to the line 5
the white wire is not good, but also the blue one
Yes, i know, ive changed it like on the first pic.
Red +12 on 4
Blue GND on 3
White -12 on 2 Thats the right way, or i am blind and check nothing 
ok so with less resonance it will be working !
I hope so, first i try to change the resistor on the input maybe it helps.
Here’s another MS-20 question… I’ve seen schematics like the Barton BMC55 call for 6 clipping diodes, but this stripboard and a lot of other kits only call for 2 LEDs.
What’s the difference between using 2 Vs 6 diodes? I figure Korg wouldn’t use 4 extra diodes if they didn’t have to.
I’m waiting for some parts to put my filter together, but I was planning to bread board it both ways and see. Has anyone else done that comparison?
2 Likes
Each diode has a 0.7 V drop. Putting three of them in series gives you a 2.1 V drop that needs to be overcome before that feedback path opens. This is similar to the voltage drop of a (old style, low intensity) green LED.
3 Likes
I see, that makes sense.
1 Like
Hello, super basic question here about the jacks. Should I use all 1/4" sockets, or does the cv need to be eurorack? I make guitar pedals but have been asked to make this for someone. He uses a lot of 1/4" stuff like guitar pedals with his synths, so if I can make them all 1/4" I would prefer it. Thanks!
The jacks don’t care what the CV voltage is. It does use the same control voltage levels as Eurorack but there is no necessity for the jacks to be 3.5 mm. 1/4" is fine. But you maybe should check with your client to find out what equipment they plan to plug into it and what kind of jack they would prefer. Is it a Eurorack or Eurorack compatible (e.g. Kosmo) synth?
1 Like
Thank you so much for the quick response! That seemed like the obvious answer to me but I didn’t want to make any assumptions. Sent the client an email asking what his preference is. Will post the build when it’s complete, this thread has been immensely helpful.
1 Like
The larger voltage drop also means less clipping and compression. The difference in sound should be very noticeable in a filter circuit.
1 Like
That’s a great point I can take down the road with me, thanks. I felt pretty dumb when asked about all this by the client. My engineering schooling was robotics club as a kid, guitar pedals were self taught and just for fun and for friends, so I’m just an ignoramus who can solder and follow directions. Learning now though because it’s fun!