PS-3300's filters are very closely related to the Korg MS-10/20 filters. These are known for their super aggressive and squelchy tonality. The circuit design is almost identical in the PS-3300, but interestingly, Korg chose to implement it with far lower gain, resulting in a much cleaner tonality - perhaps they were concerned that the many notes of polyphony combined with raunchy distortion wouldn't go together. Since it was relatively easy to implement, we've given users the option of the clean PS-3300 or aggressive MS-20 filter tones (because we think that distorted MS filter mayhem sounds pretty neat with a poly synth).
If you're not familiar with how filters work, a lowpass filter allows frequencies below the cutoff frequency setting to pass through, but blocks frequencies above the cutoff frequency.
Cut Off Frequency- All frequencies lower than the current setting are allowed to pass through the filter, while frequencies higher than the cutoff setting will be attenuated at a rate of 12 dB per/octave.
Peak (resonance)- Emphasizes sound energy at and around the cutoff frequency by adding feedback from the filter’s output back to its input. Dialing up Peak is useful for thinning out sounds a bit, and sweeping the Cut Off Frequency results in the familiar funky "weeoow" analog synthesizer sound. Resonance will be far more pronounced when the filter type is set to MS mode.
Type- The PS setting is a super-accurate emulation of the original PS-3300 sound and is generally very clean.
The PS setting also enables an under-the-hood preset highpass filter in order to accurately emulate the tone of the original, which generally didn't have a great deal of low-frequency response.
The MS setting cranks the gain up considerably in order to emulate the famous snarling MS-20 sound (these are gain compensated so MS and PS volume levels will be relatively consistent). If you haven't used an MS-20-type filter, they sound awesome with the Peak control cranked. The MS setting also disables PS-3300's aforementioned built-in highpass filtering in case you desire a little more low-end oomph.
Kbd Filter Bal- This allows the keyboard CV to modulate the cutoff frequency. When set to positive values the cutoff frequency rises as higher notes are played on the keyboard, in order to keep tonality consistent. When set to negative values, the cutoff frequency gets lower as higher notes are played.
At max resonance settings, it also allows the ringing resonant frequency to play in tune across the keyboard (this is more noticeable when Type is set to MS).
Env Mod- Turning this control up allows Envelope Mod to modulate the cutoff frequency. The higher the setting, the greater the filter cutoff frequency modulation will be.
Cutoff Frequency Modulation Controls/Jacks
On switch- The orange On slide switch enables cutoff frequency mod when in the down position.
MG1- Sets the amount of cutoff frequency mod from Mod Generator 1.
Ext- Sets the amount of cutoff frequency mod from the Ext Cut Off Control mod input jack when a source is patched.
Ext Cut Off Control- Allows CV control of the Cut Off Frequency. This is a bipolar input that accepts CV's from -5V to +5V; negative CV's will decrease cut off frequency and positive CV's will increase it.