From the Oakley website:
The Superladder is a voltage controlled transistor ladder filter. Cut-off frequency and resonance are both voltage controlable.
The VCF may be built as a 1U filter core or as a complete 3U filter system. Although the 1U module can be used as a filter module on its own, it is expected that users will make use of external mixers to control CV and audio levels going into the filter.
The Superladder VCF module has a variable shape output. It incorporates a feature first seen on the Oakley Orbital prototypes. The SLOPE pot gives you an output that can be varied from one pole (-6db) to four pole (-24db), with band pass in the middle. And that’s band pass with Moog ladder warmth.
The audio output is ‘Q compensated’. This means that the output volume will not drop significantly when you turn up the resonance pot. This design uses two inbuilt VCAs to achieve voltage controlled resonance without the hassle. A beautiful sound.
I made a custom 2U Front-Panel-Express Panel for this filter. It includes audio-taper pots for a two-input signal mixer, plus separate attenuator pots for the exponential and linear CV inputs. The panel wiring is neat and tidy with the board mounted by pot brackets.