FURIA is a discrete 4-pole ladder filter and a transistor VCA with a variable response CV curve control. It isn't "just" a filter, but an all-around vintage-sounding sculpting and performing tool.

The filter section is based on the venerable E-mu Modular 2100 LPF, but unlike it, there are no ICs in the audio path - even the output stage op-amps are transistor based, both in the VCF and VCA sections. As its name suggests, FURIA has plenty of gain on tap: the INPUT LEVEL knob starts distorting around 9 o'clock and interacts with the resonance in interesting ways, while the VCA and its X10 input switch can transform the filtered sound into nasty acid basslines - no external distortion required.

You can use the filter and VCA independently or in series, with an AMP CV input that's normalled to the FREQ CV input to facilitate a LPG-like configuration. The AMP IN allows you to mix a signal into the VCA after the filter - for example, a higher register FM'd or wavefolded sine wave with a bassier filtered sawtooth from the LPF stage.

Unlike most ladder filters, FURIA's LPF is fully DC-coupled, though internal offsets may produce slight clicks at the VCA stage. To remedy that, the DIP switch on the back lets you selectively AC-couple the VCF and VCA inputs and outputs, reducing clicks and offsets for audio purposes. It also allows you to change the VCF -> VCA normalling for series, parallel or independent use.