Olivella Modular Furia | Discrete transistor filter & VCA

video upload by Tom Churchill

"Olivella Modular's Furia is a 4-pole transistor ladder filter, based on the E-mu Modular 2100 LPF designed by Dave Rossum in the 1970s, paired with a discrete transistor VCA with tons of gain. There are no ICs anywhere in the audio path, so it has an authentically vintage sound, and it distorts in a really musical way. In this video, I give an overview of Furia’s signal path and controls and build a few patches to demonstrate how it sounds.

Chapters:
00:00 Intro & patch previews
01:42 Furia overview
07:41 Pinging the input
09:41 Overdriven acid
13:54 Furia as a low-pass gate
16:39 Dirty drum machine preamp
22:00 Audio-rate cutoff modulation"

"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're 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."