Vintage Synth Explorer Forums

I'm new round here so hello to you all.

I recently got my hands on a Korg MS20 and I've got a quick question to ask. I know that the MS20 has a fairly unique filter but as I turn the resonance up the sound goes from being non-resonant to having a sort of distorted resonant sound even well before it reaches its maximum value, with seemingly no middle ground in between. The thing is I've heard demos of the MS20 which have just your ordinary run-of-the-mill wet resonant sounds but I don't seem to be able to recreate these.

Does anybody have any ideas?

The first thing to check is the potentiometer. The filter knobs get worked a lot, and it's an old machine, so it might just be sketchy contacts. Try cleaning all the pots with a GOOD electronic control cleaner spray (I recommend LPS2) and see if it makes a difference. You'll have to remove the knobs at least, even better if you open the case and spray all the pots from the rear, and turn them back and forth to work the crud off them.

If that fails you'll have to get the res. pot replaced. Any electronic keyboard repair shop could do it.

Some ms 20's esp early one's (without the screw on the front panel) have this distorted nature. To clean those pots means taking the whole synth
apart..
Without the oscillators on how does the resonance sound...?

The resonance is distorted when it is mixed with oscillator waveforms, and it is supposed to be, that IS the magic MS-10/20 filter sound.
At least on full resonance. Normal wet res bass sounds should be possible with 50% resonance or less?

But if you hear no resonance at all unless it is max, your res potentiometer (knob) is likely broken.

To hear a pure filter, set the VCOs to pulse and crank the pulsewidth all the way left or right. The MS synths have 100% pulsewidth, meaning it completely disappears on min and max. The filter will sing on its own on full resonance.
Now you should hear a pure clean tone. It won't be a sine tone though, something more electronic and woody. Another great character print of these synths.

Bitexion wrote:The resonance is distorted when it is mixed with oscillator waveforms, and it is supposed to be, that IS the magic MS-10/20 filter sound.
At least on full resonance. Normal wet res bass sounds should be possible with 50% resonance or less?

But if you hear no resonance at all unless it is max, your res potentiometer (knob) is likely broken.

To hear a pure filter, set the VCOs to pulse and crank the pulsewidth all the way left or right. The MS synths have 100% pulsewidth, meaning it completely disappears on min and max. The filter will sing on its own on full resonance.
Now you should hear a pure clean tone. It won't be a sine tone though, something more electronic and woody. Another great character print of these synths.

Well put...

Bitexion wrote:
To hear a pure filter, set the VCOs to pulse and crank the pulsewidth all the way left or right. The MS synths have 100% pulsewidth, meaning it completely disappears on min and max. The filter will sing on its own on full resonance.

You can't change the PW on osc 2, but you also can hear pure filter just turning both oscs all the way down in the mixer. No filter modulation. My LPF starts auto-oscillating from a setting of 8 onwards.

When I first got the MS-20 it showed several signs of ill-treating and many of the pots were not linear in their functioning, ie the filter sweeps were lumpy etc. Some cleaning by a qualified techie, a couple of capacitors replaced, and ready to go. The key contacts are pretty crappy though, so if you're going to open it check the contacts as well.