Liquid Foam Analog Bass Synthesizer + Groovebox

Herbs and Stones Liquid Foam

Liquid Foam from Herbs and Stones is a modular groove box, but a far cry from the typical drum machines you may be familiar with. All the inputs and outputs send and receive gate signals, with no continuous CV signals present. The dual sequencer design is not a traditional step sequencer but a pair of gate sequencers with patterns determined by the relationships between the different parts of the device. The master clock provides timing for the two sequencers. Sequencer A features two inputs that seed new data into the sequencer. Sequencer B, on the other hand, gets its sequencer data from the LFO. The relationship between the clock speed, LFO speed, and LFO pulse width determines the sequencer B outputs. Each sequencer features four gate outputs, and the sequencer linearly moves gate information through the different stages based on the clock speed.

A trio of gate inputs, ABC, determines the pitch of the VCO. Each input is weighted differently and, therefore changes the pitch by different amounts. The VCO outputs three waveforms: triangle, sawtooth, and pulse with adjustable pulse width. The two-stage wave mixer first blends between the triangle and sawtooth waveforms, and then goes into to the second wave mixer where it mixes with the pulse waveform. This passes into a resonant 12dB/oct low pass filter whose pitch is influenced by the envelope. The filter is squelchy and reminiscent of a 303 filter. Finally, the signal passes into a CMOS-based overdrive circuit that adds warmth and additional texture.

The envelope is a decay-only envelope generator with an inversion gate input. The envelope is triggered whenever a gate is present at the ABC inputs. When the inversion gate input receives a high signal, the envelope is inverted, with the offset knob controlling how much of the inverted signal passes to the filter. The EG-VCO input directly routes the envelope to the oscillator’s pitch, bypassing the ABC gate inputs. Liquid Foam offers a unique take on a groove box, bringing together traditional and esoteric synthesis methods.

Liquid Foam Features

• Modular groovebox
• Two gate sequencers
• X and Y inputs determine sequencer A’s outputs
• The LFO determines sequencer B’s outputs
• Uses banana jacks: 5x banana cables included
• Decay-only envelope with inversion and VCO routing on gate inputs
• VCO with three gate inputs to sequence pitch
• VCO wave mixer
• Resonant low pass filter
• CMOS over drive
• Externally clockable with 3.5mm jacks