Morphor Plectrum – Analogue BBD Pluck — a fully analogue Karplus-Strong voice module in an 8HP Eurorack format, successor to the AP-1, 2HP slimmer and with added CV control over feedback. A noise burst from the trigger feeds into a loop built around an authentic BBD circuit driven by an internal VCO with 1V/oct tracking, filtered by the Colour section and fed back into the loop through adjustable feedback. Tune, colour and feedback all carry CV inputs, and trigger pulse width shifts the attack character - from short, string-like plucks to longer, more unstable tones. The frequency range spans sub-audio up to roughly 800 Hz.
A complete Karplus-Strong model in one module
Classic Karplus-Strong synthesis needs a noise generator, a delay line, a filter, and a feedback loop - in a modular rig that usually means several separate modules and a fair amount of patching. Plectrum closes that entire chain into a single 8HP module built on an authentic BBD, ready to fire from a single trigger. Short pulses give tones close to a plucked string or acoustic bass, longer ones bring rawer, more exploratory attacks - just change the trigger length, no mode-switching required.
A loop broken out for further shaping
The built-in Colour filter limits the range of tones available without extra patching. The internal/external loop switch lets you route the signal out of the Karplus-Strong circuit, through an external filter or effect, and back into the feedback loop. This means the string character is no longer locked inside the module - resonances and tones out of reach for purely internal models become possible, while the BBD core still handles the analogue character.
KEY FEATURES
- 100% analogue signal path built on a classic BBD chip
- Karplus-Strong synthesis
- Internal/external loop switch for break-out
- Trigger input with variable length shaping attack character
- 1V/oct input and tune knob
- Pitch modulation CV input
- Feedback CV input
- Colour CV input (internal loop filter cutoff)
- Mono output
TECHNICAL SPECIFICATIONS
- Width: 8 HP
- Height: 3U
- Module depth: 40 mm
- Panel dimensions: 128.5 x 40.3 x 40 mm
- Mass: 107 g
- Frequency range: sub-audio up to roughly 800 Hz
- Power socket: 16-pin
- Current draw: +12V 40 mA, -12V 40 mA, +5V 0 mA
