The Frostwave Resonator from Australia is in fact a "true clone" of the Korg MS-20's classic VCF analog filter section. It consists of a high and low pass filter in series, with resonance and cutoff controls for each, plus a balance control and bypass switch.
It looks like one big fat guitar stomp box! It's got four knobs to adjust the Frequency Cutoff and Resonance for each filter, as well as an overall Volume knob and Wet/Dry Mix knob.
There are also six 1/4" jacks on the Resonator for audio and control. A mono input, mono output, and Control Voltage (CV) inputs for the low pass cutoff and resonance and high pass cutoff and resonance. These CV inputs let you control the resonator with other analog synths.
This stomp box really is a cost-effective way to get the MS-20's classic filter to process your own synthesizers, guitars, bass, sampler, and vocals! It is used by Charlie Clouser of Nine Inch Nails.
Demos & Media
Images from Analog Effects.