Introducing the WMD Synchrodyne, a multi part and multi use eurorack module for the creation and manipulation of audio. Containing several pieces to a traditional synthesizer voice, the Synchrodyne is a powerful addition to any subtractive oriented system. However, it is designed primarily as an experimental sound source/filter, intended to push the limits of modular synthesis...
Features:
- Front End Linear VCA
- Switchable Four Stage WaveFolder
- TempCo Sawcore VCO
- Linear (AC/DC) & Expo (DC) FM
- Bipolar Attenuators for FM
- Calibrated 1V/Oct Input
- Hard Sync Input
- VCO Range ~.02Hz - >=400kHz
- Phase Locked Loop
- PLL Frequency Multiplier/Divider
- Variable Slew & Damping in PLL
- Switched Capacitor Filter
- Multimode Filter Output
- -12 & -24 dB/oct Output Taps
- Stable Self-Oscillation at -24dB/oct
- Voltage Control of Filter Resonance
- Single Stage WaveFolder on Outs
- Expandable
The Synchrodyne is designed as a way to implement a switched capacitor filter (SCF) chip without the use of a microcontroller to run the clock. WMD developed a fast analog VCO that can drive the SCF with a broad range of frequency control. The problem with this would be that the VCO is then dedicated to only running the filter. So WMD designed a frequency multiplier based around a Phase Locked Loop IC (PLL) to take the VCO and multiply its frequency up so that the VCO could be used as an audio source, while still controlling the filter. The SCF has a frequency ratio of 50:1 or 100:1 clock frequency to output cutoff frequency. The PLL allows for many ratios of input to output frequencies to be selected, making the VCO a simultaneous audio and control source.
The PLL presented its own challenges. Taming the PLL to stabilise at high multiplication ratios required us to develop a damping circuit. The damping and track speed controls give the PLL its own sound, a sort of slew limiter and self-frequency modulation. WMD wanted the Synchrodyne to distort nicely at audio input and also to self-oscillate. They added single stage rectifiers to the -12dB and -24dB filter outputs for a more aggressive sound. They decided to develop a VCA and Wavefolder for the front end of the filter to further expand the Synchrodyne's distortion and processing palette.
