Two Touch + Weevil + FilterQamp Mini System

Mini Systems by Bugbrand

Example setups – so many options!

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Two Touch + Weevil + FilterQamp Mini System

A lovely little chaos box with touch control. You may also want to consider the DPre rather than the 2Touch.

TWO TOUCH

The Two Touch features a pair of capacitive touch/pressure controls – similar to older designs like the Old-Blues CTL1 and Joystick/Touch.

Each behaves exactly the same – there is a 0 to +10V output for Pressure along with a toggling gate output (0V to c.+7.5V)  which goes on or off with each touch event (could be seen as a divide by 2).

Sensitivity can be adjusted with a trimmer on the rear – it should not need too much adjustment.

Size: 1FW
Current: +ve 27mA, -ve 5mA

WEEVIL

• Description

Back in the Old-Blues days, I tried to port the Weevil design into the modular format but it was a challenge.. The circuitry of the regular Weevils is really very simple & the chaos comes from circuit-bending (an unconventional approach!) – the difficulty was how to add voltage-control features to this simple circuitry (modular approaches are quite a bit more involved). So while I did a design back then which was enjoyed by bug-users (SYN1 Weevil), I never thought it quite captured the chaotic sonic worlds of the ‘true’ Weevils.

For a few years I put the Weevils to bed, but have recently come back to thinking on them – so, looking again at modular approaches, I’ve come up with something that I feel works things a bit differently and, while it still feels a bit different from more regular/simple Weevils, it offers a whole host of chaos & noise.

See the block diagram!

First off we have the power starvation core – this unfortunately couldn’t viably be voltage-controlled. Turn the Starve dial fully clockwise for regular/full-power usage. When starved, everything goes a bit nuts, everything interacts & we get to much more noise-based areas, though note that all outputs pass through circuitry to ensure they remain ‘full-strength’ (all are 0V to +10V). There is also a Stable switch which adds a little smoothing – it isn’t exactly stable, but it is more-so/different.

There are two voltage-controlled oscillators ranging from c.0.5Hz to 20kHz from the front panel (they can go slower with external negative CV). There are CV inputs with depth controls & polarity/mute switches for each Osc plus a CV Both input which affects both Oscs. The Oscs track 1V/Oct reasonably well, but are not temperature compensated, nor do they have the best high-frequency tracking. The two Oscs interact a little, especially so when starved. Each Osc has an independent banana output + LED indicator.

The basis for Weevils was a simple cymbal noise-source generator which quasi-ring-modulated square waves together for richly (en)harmonic tones. Here we have a first RM combining the two Oscs, followed by a second which mixes RM1 with an external signal which has passed through a drive/squaring circuit so that it matches the Weevil-core (inc. starvation). This audio input is quite level dependent so do play with the Drive control – you can also input gates/clocks/etc. to the input which can generate some interesting behaviours when using Starve. Note that without an input signal, the output of RM2 will appear quiet (ie. it isn’t silent, but it isn’t regular amplitude).

All in all, the Weevil Module is inherently quite chaotic compared with my other module designs – that is, I feel, its strength & interest! Experiment, feed different signals in, feed outputs back into CV inputs, etc.

Size: 2FW
Current: +ve 25mA, -ve 15mA

FILTERQAMP

The FilterQAmp (FQA) combines a 2-pole State Variable VC Filter with a Linear VC Amplifier and an inbuilt variable-decay Envelope Generator. It is capable both of processing and, when the filter is self-oscillating, generation of synthesised sounds such as drums.

The VCF section contains a State Variable Filter (similar to my other designs) – this offers switchable Low or High Pass responses and covers the full audio range. It is temperature compensated & tracks 1V/Oct accurately. The Resonance/Q is voltage controlled with a linear response up to self-oscillation – this creates a pure sinewave, useful for synthesis.

The VCA is linear in response and takes the Low/Hi-pass output from the VCF section. It can either be set, via rear jumper, to a clean response (gain from 0 to +1) or saturation (gain from 0 to +1 then +/-5V zener clipping beyond – unity at approx 10 o’clock rotation).

The Filter, Q and Amp sections each have a CV Modulation depth control with switchable polarity (centre off) – the Filter has an additional 1V/Oct control input. In addition there is a simple variable-decay Envelope Generator which can be fired either with the manual Trig button or via the Trig input – this has a comparator so triggers on any signal over c.+1V. Decay time is variable between approx 15mS and 3Secs with an amplitude of 0 to +10V. The envelope is internally routed to modulate the Filter and Amp sections via individual depth controls – it could be manually patched to QCV with a 0.75″ shorting bar or cable.

When Q is set to full, the self-oscillating filter makes good sound generator – it can also ring when set below self-oscillation & fed with sharp edges such as gate signals. A basic drum synth can be achieved with self-oscillation and the decay envelope opening the VCA – try varying how much the envelope modulates the filter cutoff too. You can feed the main output back to the FCV input to self-modulate, resulting in an interesting peaky waveform.

Size: 2FW
Current: +ve 50mA, -ve 50mA