Olivella Modular Furia

 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. 

• Width: 8HP
• Depth: 25mm
• Power: 25mA @ +12V / 35mA @ -12V

Features:

• Fully discrete transistor-based architecture; no ICs in the audio path.
• 4-pole (24dB/oct) low-pass ladder filter inspired by the E-mu Modular 2100 LPF.
• Integrated voltage-controlled amplifier with transistor output stage.
• Adjustable control curve for both filter and VCA modulation.
• Filter and VCA can be used separately, in parallel, or cascaded (series).
• DIP switch allows configuration for series, parallel, or independent filter/VCA paths.
• DIP switch enables AC or DC coupling of VCF and VCA inputs/outputs to manage clicks and offsets.
• Input Level control introduces distortion around 9 o’clock for rich, characterful drive.
•  Input gain and resonance interact dynamically for expressive tone shaping.
• Boosts input level for aggressive, overdriven sounds—ideal for acid-style basslines.
• AMP CV input normalled to FREQ CV input for low-pass gate–like behavior.
• Secondary input allows blending of an additional signal into the VCA post-filter (e.g., for layering tones).
• Fully DC-coupled signal path for CV and audio-rate modulation.