Sin Phi - Blight

Blight: Resonant Low Pass Gate

Blight: Resonant Low Pass Gate The Miasma is an extremely versatile module. This design is based on the Befaco Rampage. At its core the Miasma is a pair of bi-directional slew integrators. The Miasma has a broad range of patch programibility from oscillators and envelopes to envelope followers and low pass filters.

The Miasma features inputs for rise, fall and exponential control voltages that change the shape of the wave-forms output. The rise and fall control voltages have attenuverters and offset potentiometers. The range switch selects between fast, mid and slow rates. Shape of the waveform can be set with a potentiometer from exponential rise and logarithmic fall, linear rise and linear fall, or logarithmic rise and exponential fall. Input for the trigger starts the cycle. The trigger momentary switch can trigger either side. A The cycle input inverts the cycle switch which selects between looping or singular.

The Miasma outputs for each function generator are rising and falling gates, end of cycle trigger and bipolar output. The balance potentiometer sets the level going into the analog minimum, maximum, left greater than right comparator and an AD633 four quadrant multiplier.

CC BY-NC-SA 4.0


Schematic

PDF Main Schematic

PDF I/O Schematic


PCB Layout

KiCAD Files

VCO PCB VCO Face

Panel Design

SVG Front Panel

PDF Front Panel


Bill of Materials

PDF Bill of Materials


Tuning and Calibration

Connect the OUT output to an oscilloscope. Use the mid setting of the RANGE switch. Set to cycle on the CYCLE switch and use the manual trigger TRIG switch. Set rise and fall to minimum. Turn the SHAPE potentiometer fully clockwaise. Rise and fall times should be equal. If they are not adjust the symmetry trimmer. Repeat for the other side.


Patch Programming

Envelope Generators

Attack-Release Envelope Generator: For an AR envelope patch a trigger into the TRIG input. An AR envelope is generated at the OUT with the attack and release controlled by the RISE and FALL pots respectively.

Attack-Sustain-Release Envelope Generator: An ASR envelope can be made by patching a gate into the IN input. The output will sustain as long as the gate is high. Attack and release are again controlled by RISE and FALL pots.

Complex Envelopes: Complex envelopes can be created by mixing the outputs of more than one slope generator together. As an example one half of the Miasma could handle the attack and decay while the other performs the sustain and release.

Low Frequency Oscillators

To make an LFO first patch the GATE OUT into the TRIG. The slope generator will start to oscillate with the frequency determined by the RISE and FALL pots.

Square Wave LFO: To take the square wave output just patch into the GATE OUT jack.

Triangle/Saw Wave LFO: To take the triangle/saw wave output just patch into the OUT jack. The shape can be controlled by adjusting the RISE and FALL pots. A short rise and slow fall giave a saw waveform, a slow rise and quick fall gives a ramp and equal times a triangle. This shape can be modulated by patching a control voltage into the CV; with the modulation target controlled by the RISE:BOTH:FALL switch.

Complex Wave-forms: Composite waves from more than one slope generator can be mixed to create new wave-forms.

Soften Wave-forms: to create 'softer' triangle and square wave-forms the LFO output can be run through a slope generator programmed as a Slew Generator.

Audio Rate Oscillator

Set up the DUSG like an LFO and then use a control voltage on the PITCH jack. The oscillator will not track especailly well, but it is much better at base to mid tones than high frequencies.

Trigger/Gate Delay

Patch a trigger or gate signal into the TRIG jack and take the delayed signal from the GATE OUT jack. The amount of delay is set by the sum of the RISE and FALL pots. Output may need to be inverted if the falling or rising edge is desired.

Subharmonic Generator

This is set up similar to the Trigger/Gate Delay so that the DUSG can be re-triggered by an audio signal and the output will be a square wave that is a sub-harmonic of the original signal. Patch an audio signal into the TRIG jack and take the output from the GATE OUT jack. This will have to be tuned and input signal may need to be squared up.

Envelope Follower

Patch a auido signal into the IN jack and set the RISE pot to fast. Set the FALL pot to fast and turn down until the signal at the OUT jack follows the waveform of the audio input signal.

Directional CV Glid

Patch the control voltage into the IN jack and the slewed signal will be on the OUT jack. The RISE and FALL pots control the slew up or down respectively. The output signal can be used to control an oscillator's pitch creating glide or portamento. The Portamento doesn't have to be bipolar; it can be just on the up, the down or asymmetrical. To achieve an exponential response stack a patch cable from the OUT jack to the CV jack and adjust the curve with the CV LEVEL pot.

Low Pass Filter

A lo-fi low pass filter can be created with this patch by setting RISE and FALL pots relatively fast. Use the control voltage inputs for voltage control of the filter.

Lopsided Recursive Waveform Generator

Patch an LFO on both halves of the DUSG. Patch the output of each half of the DUSG into the CV of the other half. Stack a patch cable onto one of the outputs and use a lopsided recursive waveform.

Chaotic Waveforms

Cross-connecting two Slope Generators together generates interesting 'chaotic' wave forms. Connect the output of one to the attenuated VC input of the other, then take the output of the second and patch it to the input of the first. Play with the attenuator settings.