frap-tools/brenso

Brenso

Frap Tools

Dual analog triangle-core through-zero oscillator with a timbre modulation section (waveshapers, PWM, wavefolder) and a four-quadrant multiplier for amplitude and ring modulation, offering eight waveform outputs and extensive internal and external modulation routing.1069

Capabilities 7

Complex Oscillatorcomplex-oscillator
1069
FM Sourcefm-source
1069
LFOlfo
Green oscillator has a low-frequency scale mode (~0.15–40 Hz) for use as a complex LFO.1069
Oscillatoroscillator
Two analog triangle-core through-zero oscillators track over more than 6 octaves and can run at audio or sub-audio rates.1069
Ring Modulatorring-modulator
Four-quadrant multiplier can perform amplitude modulation (two-quadrant) or ring modulation (four-quadrant) with the green sine wave as default modulator.1069
Wavefolderwavefolder
Pingable wavefolder with symmetry control processes the yellow oscillator's timbre output; can be excited by external triggers for nonlinear decay envelopes.1069
Waveshaper / Wavefolderwaveshaper
1069

Jacks 30 (21 in / 9 out)

NameSignalVoltageDescription
Inputs (21)
AM/RM CV Inputcv1069
AM/RM Inputmixed1069
Exponential FM Input (Green)cv1069
Exponential FM Input (Yellow)cv1069
FM Deviation CV Input (Green)cv1069
FM Deviation CV Input (Yellow)cv1069
Linear TZFM Input (Green)cv1069
Linear TZFM Input (Yellow)cv1069
Modulation Bus Inputcv1069
Modulation Bus Level CV Inputcv1069
PWM CV Inputcv1069
Pulse Shaper CV Inputcv1069
Sync Inputaudio≥2V1069
Triangle Shaper CV Inputcv1069
V/Oct Input (Green)cv1069
V/Oct Input (Yellow)cv1069
V/oct Integrator CV Inputcv1069
Wavefolder CV Inputcv1069
Wavefolder Ping Inputtrigger1069
Wavefolder Source CV Inputcv1069
Wavefolder Symmetry CV Inputcv1069
Outputs (9)
Final OutputaudioOutputs the yellow oscillator's signal after routing through the Timbre Modulation and Amplitude Modulation sections; the primary output for processed yellow oscillator sound.1069
Modulation Bus Outputcv1069
Sawtooth Wave Outputaudio1069
Sine Wave Output (Green)audio-5V to 5V1069
Sine Wave Output (Yellow)audio1069
Square Wave Output (Green)audio1069
Square/Shaped Pulse Outputaudio1069
Triangle Wave Output (Green)audio1069
Triangle Wave Output (Yellow)audio1069

Parameters 27

NameTypeRangeBehavior
AM/RM Crossfaderknob-10V – 10VBlends between the dry wavefolder signal (left) and the amplitude- or ring-modulated copy of it (right). Fully left gives the unmodulated wavefolder output; fully right gives only the four-quadrant multiplier output.1069
AM/RM SwitchswitchSelects between amplitude modulation (upper position, two-quadrant/unipolar modulator) and ring modulation (lower position, four-quadrant/bipolar modulator).1069
Coarse Frequency (Green)knob27.5Hz – 7040Hz1069
Coarse Frequency (Yellow)knob27.5Hz – 7040Hz1069
Coarse Frequency Lock (Green)buttonWhen pressed, digitally samples and holds the Coarse Frequency knob voltage, preventing accidental detuning. The oscillator's pitch then responds only to external CV or internal FM. Press again to unlock; if the knob moved, the new position takes effect.1069
Coarse Frequency Lock (Yellow)button1069
Exponential FM Attenuator (Green)knob1069
Exponential FM Attenuator (Yellow)knob1069
Fine Frequency (Green)knob-1semitone – 1semitoneFinely adjusts the green oscillator's pitch by more than one semitone in either direction. Not affected by the Coarse Frequency Lock.1069
Fine Frequency (Yellow)knob1069
FM Deviation (Green)knob-10V – 10V1069
FM Deviation (Yellow)knob1069
Frequency Scale SwitchswitchSelects between audio-rate and LFO-rate operation for the green oscillator. In Low mode, the frequency range is approximately 0.15–40 Hz, about 176 times slower than the audio-rate range.1069
Linear TZFM Attenuator (Green)knob1069
Linear TZFM Attenuator (Yellow)knob1069
Modulation Bus Levelknob-10V – 10VControls a VCA that sets the amplitude of the green sine wave (or external signal) routed to the four timbre CV inputs. Leftmost closes the VCA (no modulation); rightmost reaches unity gain routing the full green sine to the timbre inputs.1069
Pulse Shaperknob-10V – 10VShapes the harmonic content of the PWM pulse wave: left emphasizes low frequencies, noon reproduces the PWM wave most purely, and further clockwise progressively emphasizes high frequencies until around two o'clock where they peak, after which low frequencies are re-emphasized with inverted phase.1069
Pulse Widthknob-10V – 10VSets the comparator threshold that determines the ratio between the positive and negative halves of the PWM pulse wave. Center position produces approximately 50% duty cycle (square wave). Moving left or right creates positive or negative asymmetry.1069
PWM Source Switchswitch1069
Square/Shaped Pulse Switchswitch1069
Sync SwitchswitchThree-way switch on the green oscillator selects between no sync, Lock Sync, and Flip Sync relative to the yellow oscillator. The yellow oscillator's sync mode is set via a back-panel jumper.1069
Triangle Shaperknob-10V – 10VMorphs the yellow oscillator's triangle wave between a sine (left), triangle (noon), and logarithmic waveform (right). Output feeds both the Source crossfader and the PWM comparator.1069
V/oct Integrator LevelknobRoutes the yellow V/oct CV to the green oscillator with a variable slew/glide time. Fully left means no signal reaches green; fully right applies the exact same voltage instantly; intermediate positions introduce glide proportional to the knob position.1069
Wavefolderknob-10V – 10VControls wavefold amount. The first dotted section (leftmost to clean-waveform icon) controls amplitude from 0 to unity gain with no folding. Rotating clockwise past that point introduces progressively more folds up to the maximum at the rightmost position.1069
Wavefolder Ping DecayknobSets the nonlinear decay time of the wavefolder ping envelope. The leftmost position gives the fastest decay; turning clockwise produces a significantly longer decay.1069
Wavefolder Sourceknob-10V – 10VCrossfades between the Triangle Shaper output (left) and the Pulse Shaper output (right) as the signal fed into the Wavefolder. Noon gives a 50-50 blend; fully right retains a small amount of the Triangle Shaper signal.1069
Wavefolder SymmetryknobAdds a voltage bias to the wavefolder input to create asymmetric folding between the positive and negative halves of the waveform. Noon is perfectly balanced; clockwise emphasizes positive-half folds; counterclockwise emphasizes negative-half folds.1069

Firmware history 1 version

VersionReleasedNotes
200901Board layout rearranged to facilitate calibration procedure in the lab; functions and tech specs unchanged.1069

References 2

  1. [1069]
    Frap Tools MANUALONE (multi-module manual; Brenso section)manual
    verified 2026-06-01
  2. [1070]
    Frap Tools Brenso product pageproduct_page
    verified 2026-06-01