BlaknBlu - Foxtrot Duo MK2

Foxtrot Duo Mk 2 is a compact stereo multi-mode filter that packs three meticulously modeled classic filter circuits into one module. Through detailed virtual analog modeling, it captures Moog's ladder, Korg's Sallen-and-Key, and Oberheim's SEM filters — each analyzed from the original circuits down to their smallest quirks. The differences between them are quite clear: the ladder filter delivers warm, squelchy resonance, the Sallen-and-Key circuit moves from clean to screaming, while the SEM provides that characteristically smooth response. The digital architecture allows these filters to morph between low-pass, band-pass and high-pass modes, while still staying very precise and controlled — something much harder to do with traditional analog circuits.

New in Mk 2 is a knob and CV input for splitting the cutoff frequencies of the two filters. This works especially well in band-pass mode, where it can produce formant-like sounds. Combined with the new mono summing option — which sums the two filters to both outputs — the split cutoff becomes even more interesting, layering two different cutoff points into a single signal path.

Like their hardware ancestors, these virtual circuits respond beautifully when pushed. The Boost switch drives them into satisfying saturation — especially evident in the Sallen-and-Key filter's aggressive resonant peaks. A soft clipper with LED indicator keeps the wildest moments under control.

If you include the Aux CV input, there are now three cutoff CVs available, including a new dedicated volt-per-octave input. The auxiliary CV input also handles filter morphing, resonance or stereo positioning depending on your needs.

A versatile stereo filter that covers warm, smooth and aggressive — with enough CV and routing options to keep you busy for a while!

Features:

• Three filter models: Moog-style ladder, Korg MS-20 inspired, Oberheim SEM
• Morphing between LP, BP and HP modes
• Split cutoff control with CV for formant-like filtering
• Stereo and mono operation (mono sums both filters to both outputs)
• Three CV inputs for cutoff, including dedicated V/oct
• Aux CV for filter morphing, resonance or stereo movement
• Boost switch for saturation
• Soft clipper with LED indicator
• Dual attenuated inputs