Instruō Tš-L (Version 2) Oscillator User Manual

Description

The Instruō Tš-L is a fully analogue voltage controlled oscillator (VCO) with a plethora of features in a very small footprint. Its triangle core circuitry allows for extremely consistent waveforms over a wide frequency range. The triangle foundation is used to generate its sine waveform, which holds consistent shape and amplitude across the Tš-L’s wide range. The outputs consist of simultaneous Square/Sub, Triangle, and Sine waveforms, with an additional voltage controllable wavefolder and a complex PWM waveshaper.

The Tš-L includes every feature needed to powerfully perform as a rich, ultra-compact audio source, as well as functioning equally as a versatile modulation source.

Features

• 1V/Oct tracking
• Linear and exponential frequency modulation
• Pulse width modulation
• Wavefolding
• Soft synchronisation
• Sub-square mode
• LFO range at the push of a button

Installation

1. Confirm that the Eurorack synthesizer system is powered off.
2. Locate 6 HP of space in your Eurorack synthesizer case.
3. Connect the 10-pin side of the IDC power cable to the 2x5 pin header on the back of the module, confirming that the red stripe on the power cable is connected to -12V.
4. Connect the 16-pin side of the IDC power cable to the 2x8 pin header on your Eurorack power supply, confirming that the red stripe on the power cable is connected to -12V.
5. Mount the Instruō Tš-L in your Eurorack synthesizer case.
6. Power your Eurorack synthesizer system on.

Note: This module has reverse polarity protection. Inverted installation of the power cable will not damage the module.

Specifications

• Width: 6 HP
• Depth: 35mm
• +12V: 60mA
• -12V: 40mA

Overview

The Instruō Tš-L module is presented with a front panel diagram and a key to its controls.

Module Diagram Description: The front panel features a central circular element labeled 'Tš-L' with various knobs and jacks arranged around it. Controls are numbered from 1 to 20, corresponding to specific functions. Key controls include 'COARSE', 'FINE', '1V/OCT', 'LFO', 'SYNC', 'FM', 'SUB', 'PWM', 'PULSE FOLD', 'LIN EXP', 'CV', and 'SYMMETRY'. There are multiple input and output jacks for audio and CV signals.

Key:

• 1. Square Output
• 2. Sub Toggle
• 3. Triangle Output
• 4. Sine Output
• 5. PWM Output
• 6. Wavefold Output
• 7. Coarse (Frequency Control)
• 8. Fine (Frequency Control)
• 9. 1V/Oct Input
• 10. LFO Button
• 11. PWM CV Input
• 12. PWM CV Attenuverter
• 13. PWM Waveform Crossfade
• 14. FM Input
• 15. FM Attenuator
• 16. Lin/Exp Toggle (for FM Input)
• 17. Wavefold CV Input
• 18. Wavefold Depth / CV Attenuator
• 19. Symmetry Bias Attenuverter
• 20. Soft Sync Input

Waveforms

The Tš-L oscillator produces several distinct waveforms:

• Square Output: A standard square waveform output.
• Triangle Output: A standard triangle waveform output.
• Sine Output: A standard sine waveform output.
• Pulse Output: A pulse width modulation (PWM) waveform output.

Pulse Width Modulation Waveform Description: This unique waveform smoothly morphs between a 'Split Triangle' shape and a slightly softened 'Stepped Triangle' shape. The 'Split Triangle' waveform is characterized by sharp peaks and troughs, while the 'Stepped Triangle' waveform has a more quantized, less sharp appearance.

Wavefold Output: This is the final output waveform. Its shape is determined by the 'Wavefold Attenuator' and the 'Symmetry Bias' parameter.

Frequency/Pitch

Coarse: The 'Coarse' knob controls the fundamental frequency of the oscillator, determining the pitch of all waveforms. Turning it anticlockwise decreases frequency, while turning it clockwise increases frequency.

Fine: The 'Fine' knob provides minute control over the oscillator’s fundamental frequency, relative to the 'Coarse' setting. It also affects the pitch of all waveforms. Turning it anticlockwise decreases frequency, and turning it clockwise increases frequency.

1V/Oct Input: This is a bipolar control voltage input calibrated to 1 volt per Octave. It is traditionally used for frequency control (musical pitch) from a sequencer or keyboard. The control voltage is summed with the values set by the 'Coarse' and 'Fine' knobs.

LFO Button: Pressing the 'LFO Button' enters LFO Mode, turning the Tš-L into a low-frequency oscillator. In LFO Mode, the frequency drops, forcing all waveform outputs to oscillate within subsonic frequency ranges. The highest rate in LFO Mode is 220Hz.

Sub Toggle: The 'Sub Toggle' determines the octave of the square waveform:

• Center Position: The square waveform frequency is set to the fundamental frequency, in unison with other waveforms.
• Right Position: The square waveform frequency is set to one octave below the fundamental frequency of the oscillator.
• Left Position: The square waveform frequency is set to two octaves below the fundamental frequency of the oscillator.

Pulse Width Modulation

PWM: The 'PWM' parameter controls the width of the pulses for the PWM waveform. Turning the knob anticlockwise decreases pulse width, and turning it clockwise increases pulse width.

PWM CV Input: This is a bipolar control voltage input for the PWM parameter. Control voltage is summed with the 'PWM' knob position. The input range is –/+5V.

PWM Waveform Crossfade: This knob controls the blend between two parallel PWM-controlled waveforms produced by the Tš-L. Turning the knob anticlockwise blends towards the split triangle waveform, while turning it clockwise blends towards the stepped triangle waveform.

Control Positions and Waveshape Description: A diagram shows four control positions, each illustrating a different waveshape resulting from PWM adjustments. These range from a split triangle to a more squared-off, stepped triangle waveform.

Frequency Modulation

FM Input: This is a bipolar control voltage input for the frequency parameter of the oscillator. Control voltage is summed with the values set by the 'Coarse' and 'Fine' knobs and scaled by the 'FM Attenuator'.

FM Attenuator: This control determines the depth of frequency modulation applied to the fundamental frequency. Turning the knob anticlockwise decreases the depth of modulation, while turning it clockwise increases it.

Lin/Exp Toggle: The 'FM Input' can be set to have a linear or exponential FM response curve. A diagram shows a toggle switch: when set to the left position, the FM signal applies with linear scaling; when set to the right position, it applies with exponential scaling. If set to exponential FM and the 'FM Attenuator' is fully clockwise, the 'FM Input' will essentially track at 1V/Octave, though tracking may differ slightly from the calibrated 1V/Oct Input.

Frequency Modulation Waveform Description: An illustration shows a base sine wave being modulated by another waveform, resulting in a complex, vibrato-like sound.

Wavefolding

Wavefold: The 'Wavefold' knob controls the amount of wavefolding applied to the waveform produced at the 'Wavefold Output'. A parallel sine waveform is used by the wavefolder. Turning the knob fully anticlockwise results in a waveform that resembles a sine wave. Turning it fully clockwise results in a rich, harmonic timbre. Adjusting the 'Symmetry Bias' knob will further affect the harmonic makeup.

Wavefold CV Input: This is a unipolar positive control voltage input that can be scaled by the 'Wavefold' knob. When external control voltage is used, the 'Wavefold' knob acts as an attenuator for the external control voltage signal.

Symmetry Bias: The 'Symmetry Bias' knob controls a DC offset amount that shapes the sine waveform used by the wavefolder. This offset is applied before the wavefolding stage. The 'Symmetry Bias' parameter offsets the curvature of the raw sine waveform, which is then further shaped by the wavefolder. Applied 'Symmetry Bias' affects the harmonic makeup of the final waveform.

Soft Synchronisation/Phase Locking

The Tš-L implements Soft Synchronisation, also known as Frequency Lock or X-Lock.

• The oscillator’s core triangle waveform changes its charge direction when clocked.
• When tuning the oscillator to an external signal, the 'Soft Sync Input' can be used to phase lock signals, removing beat frequencies in unison and perfect interval tunings.
• The Tš-L will lock to integer multiples of the external signal.
• Musical intervals such as perfect octaves, perfect 4ths, and perfect 5ths work best for the 'Soft Sync Input'.
• The voltage threshold for Soft Sync is 2V.

Soft Sync Waveform Description: A diagram shows a waveform labeled 'SOFT SYNC', depicting a series of square-like pulses with varying widths, suggesting a synchronized signal.

Patch Examples

East Coast Synth Voice

Summary: A sequencer or keyboard sends voltages to the Tš-L while simultaneously triggering an envelope generator. The CV output of the envelope generator controls a filter and VCA, allowing the Tš-L's signal to pass through. More traditional East Coast patches would use separate envelope generators for the filter and VCA.

Patch Diagram Description: The diagram illustrates a Eurorack setup. The Tš-L module receives 'Gate Signal' and '1V/Oct Signal'. Its 'Square', 'Pulse', and 'Triangle' outputs are connected to the inputs of a mixer module. The mixer's output is routed to a filter module, and the filter's output goes to a VCA module. The final output is monitored.

Audio Path:

• Connect the Square, Pulse, and Triangle waveforms of Tš-L to three inputs of a mixer.
• Set the 'Sub Toggle' to its left position, dropping the square waveform by one octave.
• Connect the output of the mixer to the audio input of a filter.
• Connect the audio output of the filter to the audio input of a VCA.
• Monitor the output of the VCA.

Configuration:

• Set the fundamental frequency of Tš-L to a desired position.
• Set the individual levels of the mixer to desired positions.
• Set the cutoff frequency of the filter to a desired position.
• Set the resonance of the filter to a desired position.
• Set the level of the VCA to a desired position.

Control Path:

• Connect the 1V/Oct output of a sequencer or keyboard to the 1V/Oct input of Tš-L.
• Connect the gate output of the sequencer or keyboard to the trigger input of an envelope generator.
• Connect the CV output of the envelope generator to a multiple.
• Connect one copy of the envelope generator CV signal to the CV input of the filter and set the corresponding CV attenuator to a desired position.
• Connect a second copy of the envelope generator CV signal to the CV input of the VCA and set the corresponding CV attenuator to a desired position.
• Set the envelope stages to desired positions.

FM Synth Voice

Summary: A secondary oscillator, termed the 'Modulator', modulates the frequency of the Tš-L (termed the 'Carrier') in an FM patch. A sequencer or keyboard sends voltages to the Tš-L while simultaneously triggering an envelope generator. The CV output of the envelope generator controls a filter and VCA, allowing the Tš-L's signal to pass through. More traditional East Coast patches would incorporate separate envelope generators for the filter and VCA.

Patch Diagram Description: The diagram shows a Eurorack setup for FM synthesis. The Tš-L receives 'Gate Signal' and '1V/Oct Signal'. Its 'Sine waveform' output is connected to the 'FM Input' of another module, while its main output is connected to the final 'Output'.

Audio Path:

• Create an East Coast Synth Voice audio path using the sine waveform of Tš-L.

Control Path:

• Create an East Coast Synth Voice control path.
• Connect the sine waveform of a separate oscillator to the FM Input of Tš-L.

Configuration:

• Set the FM Attenuator to a desired position.
• Set the Lin/Exp Toggle to a desired position.

Most East Coast synthesizers were traditionally limited to linear frequency modulation only.

Folded PWM Synth Voice

Summary: Connecting the 'PWM Output' to the 'Wavefold CV Input' allows for four levels of timbre control via the 'PWM' knob/PWM CV Input, the 'PWM Waveform Crossfade' knob, the 'Wavefold' knob, and the 'Symmetry Bias' knob. A sequencer or keyboard sends voltages to the Tš-L while simultaneously triggering an envelope generator. The CV output of the envelope generator controls a filter and VCA, allowing the Tš-L's signal to pass through. More traditional East Coast patches would incorporate separate envelope generators for the filter and VCA.

Patch Diagram Description: The diagram illustrates a Eurorack patch where the Tš-L module's 'PWM Output' is connected to the 'Wavefold CV Input' of the same module, enabling timbre control through PWM and wavefolding parameters. Standard 'Gate Signal' and '1V/Oct Signal' inputs are shown, with the final signal routed to 'Output'.

Audio Path:

• Create an East Coast Synth Voice audio path using the Wavefold Output of Tš-L.
• Set the 'Wavefold' knob to a desired position.
• Set the 'Symmetry Bias' knob to a desired position.

Control Path:

• Create an East Coast Synth Voice control path.
• Connect the Pulse Output to the Wavefold CV Input.
• Set the 'PWM' knob to a desired position.
• Set the 'PWM Waveform Crossfade' knob to a desired position.

Manual Information

Manual Author: Collin Russell

Manual Design: Dominic D’Sylva

This device meets the requirements of the following standards: EN55032, EN55103-2, EN61000-3-2, EN61000-3-3, EN62311.