The volume changes when the analog filter ACTIVE button is turned ON.

hen the volume lowers
Lower the RESONANCE knob level. The circuit is constructed so that for large adjustments to resonance values, only the frequencies close to the cutoff are amplified, and sounds from other frequency bands cancel each other out. To prevent the volume of specific frequencies from becoming too loud, adjust the overall volume balance.

When the volme increases
Lower the DRIVE knob level. It is adjusted that when the drive value is large, the volume sent to the analog circuit is high.