Description

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 is unique in that the audio path is fully discrete with no op-amps – even the output stage op-amps are transistor based, both in the VCF and VCA sections.
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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 an LPG-like configuration. 

The AMP IN allows you to mix a signal into the VCA after the filter – a useful example use case could be: 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.

FURIA – Build Document | Modular Grid

Features:

• Fully discrete 4-pole, -24dB/oct ladder filter, with CV input and attenuverter
• “Vintage” transistor core voltage-controlled amplifier, with CV input and attenuverter
• Pre-filter saturation via the INPUT LEVEL knob
• AMP CV variable response curve control from linear to exponential
• X10 switch reduces the VCA’s inputs impedance tenfold, enabling distortion or pre-amplification of external sources
• AMP IN normalled to FREQ IN
• DIP switch allows for AC-coupling of inputs / outputs and changing the VCF -> VCA normallization

Specs:

• Width: 8 HP
• Depth: 25 mm
• Power draw: +12V: 25mA, -12V: 35mA
• DC / AC-coupling selectable via back jumper
• All CV inputs allow audio-rate modulation
• Input impedances: 10 kΩ / 100 kΩ (AMP IN), all others 100 kΩ
• Output impedance: 1 kΩ
• Reverse power polarity protection
• 2 mm anodized aluminium panel