Schräg (Schraeg)

Multimode filter with character switches, based on the Bastl Cinnamon

Schräg (also know as Schraeg, for the umlaut-deficient) is effectively a repackaged Bastl Cinnamon:

• Multimode filter with independent outputs (2-pole LP, 2-pole HP, 1-pole BP)
• V/oct input
• Self-resonates for use as a sine oscillator
• Input with an attenuator and 5x gain switch
• Two character switches for altering the resonance tracking
• All-SMD construction in a DIY-friendly format, with 0603 handsoldering footprints, all components on the back of the circuit board
• Built mostly using standard and easily-available components

with a few modifications:

• larger 8HP form factor, allowing for a big juicy cutoff knob
• Voltage control over resonance, through an attenuverter
• FM input through an attenuverter, which works as a pitch fine-tune control with nothing patched
• Larger character and gain switches
• A bi-directional power connector, with polyfuses
• An Interactive BOM to aid in part placement

The additional functionality is achieved with a minimum of extra components, thanks to the two unused VCA cells in the original design.

The schematic, board layout and graphics are released under a cc-by-sa license. Bastl Instruments generously gave their permission for me to release my rework of their module. They’re a cool company. Go check out their work!

https://github.com/barnabywalters/Schraeg