The stock Korg filters are fine, but suppose we wanted a more versatile filter such as an SV filter, but with that distinctive Korg MS20 style growl and scream?
I can’t promise this is going to sound the same as the Korg, but it does have a wild overdriven sound to it. There’s only one 3rd party module used, the DAM Waveshaper NL (Thanks Davidson it’s a great addition to SE!)
The principle is fairly simple it’s a gain control on the input feeding the first SV filter which then feeds into the waveshaper. The first filter and the waveshaper can be switched out to give a clean SV filter sound.
Normal/Saturated switching.
On switching the extra filter and waveshaper in we can get the overdriven sound by adjusting the gain, the filter resonance (labelled Saturate) Note: You could leave it set as the default maximum of 10V but I found this tended to get a little too unpredictable. A maximum of 8 volts is plenty. Increasing the resonance will naturally increase the distortion from the waveshaper, but this is also controllable via the Tanh control. (I found the best waveshaper mode to be Tanh).
Second filter.
Nothing much to say here, it’s best however to keep the maximum resonance level to about 8 V to avoid self-oscillation.
Modes.
If like I have you want to make this a Low/High/Band/Notch filter then make sure both filters are connected to switch modes.
1/2 Stage switch.
Best results for my ears came from just switching the output filter between 1 and 2 stage. I thought switching both made the filter to “thin” and shrill to be very musical.
Control voltages.
I kept the CV inputs down to controlling Pitch and Tanh, but feel free to experiment.
Note: I tried adding an Pitch offset to the first SV filter in the chain, but I found the results were not too different.
Important note: When experimenting with this filter please, please, please keep the volume low until you are familiar with it. It will probably produce unexpectedly high volumes when resonant filter peaks start saturating. I would not like anyone to damage their hearing!
