INSTRUo larachd Input Utility User Manual
- June 5, 2024
- INSTRUO
Table of Contents
INSTRUo larachd Input Utility
Description
The Instruō làrachd is a fully analogue multifunction utility module that
provides various methods of interfacing external signals and interactions into
musically useful control voltage signals.
It features a stereo line level to dual mono modular level converter,
condenser microphone, audio enhancer, envelope follower, threshold comparator,
and dual footswitch interface (footswitch included), làrachd is a true “Swiss
Army knife” that finds a purpose in every patch.
Whether you’re looking to process line level signals with your modular
effects, control your processors like filters and VCAs with acoustic signals,
or hands-free record on arbhar or Lúbadh, làrachd is your all-in-one solution.
Features
- Stereo line level to dual mono modular level conversion
- On-board condenser microphone
- Audio enhancement circuitry
- Envelope following with threshold comparator derived gate
- Dual footswitch interface
- Included dual footswitch
Installation
- Confirm that the Eurorack synthesizer system is powered off.
- Locate 8 HP of space in your Eurorack synthesizer case.
- Connect the 10 pin side of the IDC power cable to the 2×5 pin header on the back of the module, confirming that the red stripe on the power cable is connected to -12V.
- Connect the 16 pin side of the IDC power cable to the 2×8 pin header on your Eurorack power supply, confirming that the red stripe on the power cable is connected to -12V.
- Mount the Instruō làrachd in your Eurorack synthesizer case.
- 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: 8 HP
- Depth: 30mm
- +12V: 75mA
- -12V: 70mA
A range of operation, a marked effect, impression, or impact
Key
- Stereo Line Input
- Stereo Level
- Left Output
- Right Output
- Output LED
- Source Toggle
- Microphone
- Enhance Input
- Enhance Level
- Enhance Output
- Envelope Follower Input
- Response Curve Switch
- Attack
- Release
- Positive Envelope Output
- Negative Envelope Output
- Comparator Threshold
- Comparator Gate Output
- Dual Footswitch Input
- A – Button
- B – Button
- A – Button Trigger Duration
- A – Button Trigger Output
- A – Button Trigger LED
- A – Button Gate Output
- A – Button Gate LED
- B – Button Gate Output
- Latching Gate Button
Level Conversion & Audio Enhancement
Stereo Line Input: Stereo input for line level to modular level conversion.
- The signal present at the Stereo Line Input (TRS 3.5mm) will be split and output from the Left (TS 3.5mm) and Right (TS 3.5mm) Outputs.
- If the Right Output is unpatched then its signal will sum with the Left Output as a mono source.
- A mono sum of the stereo signal present at the Stereo Line Input can be used as the normalled input source for the Enhance Input and the Envelope Follower Input based on the setting of the Source Toggle.
Stereo Level: Manual level control for the signal present at the Stereo Line Input.
- Turning the Stereo Level knob clockwise increases the input signal.
- Fully anti-clockwise will set the throughput gain to approximately unity level of the stereo line source.
- The available gain range is approximately +40dB.
Left Output: Mono split output of the stereo signal (Tip) present at the
Stereo Line Input.
Right Output: Mono split output of the stereo signal (Ring) present at
the Stereo Line Input.
Output LED: LED indication of the signal present at the Left Output.
Source Toggle: Toggle that switches the normalled input source of the
Enhance Input and the Envelope Follower Input.
- If the toggle is in the up position, a mono sum of the stereo signal present at the Stereo Line Input is the normalled input source of the Enhance Input and the Envelope Follower Input.
- If the toggle is in the centre position, input source normalling to the Enhance Input and Envelope Follower Input is muted.
- If the toggle is in the down position, the Microphone is the normalled input source of the Enhance Input and Envelope Follower Input.
Microphone: On-board condenser microphone.
- The Microphone can be the normalled input source for the Enhance Input and the Envelope Follower Input.
Enhance Input: Mono input for audio enhancement.
-
Similar to arbhar and Lúbadh, làrachd’s Enhance Input is based on tangential distortion limiting circuitry (as used in tanh[3]). This circuit is used for soft clipping, limiting, and waveshaping. Further non-linear shaping and gentle filtering is applied through this
signal processor. -
If no signal is present at the Enhance Input, either a mono sum of the signal present at the Stereo Line Input or the Microphone signal can be chosen as the normalled input source.
-
If a normalled input source is active, patching a connection to the Enhance Input will break the normal.
Enhance Level: Manual level control for waveshaping over the signal
present at the Enhance Input or the normalled input source.
Enhance Output: Mono output of the audio enhancement circuit.
Envelope Following
Envelope Follower Input: A signal present at the Envelope Follower Input will generate an envelope signal at the Positive and Negative Envelope Outputs.
- If no signal is present at the Envelope Follower Input, either a mono sum of the signal present at the Stereo Line Input or the Microphone can be chosen as the normalled input source.
- If a normalled input source is active, patching a connection to the Envelope Follower Input will break the normal.
Response Curve Switch: Switch that determines the response curve of the variable envelope signal generated at the Positive and Negative Envelope Outputs.
- If the switch is in the left position, a linear response curve will be selected
- If the switch is in the right position, a logarithmic attack/exponential release response curve will be selected.
Attack: Manual attack time control for the generated envelope signal.
- Changes to this parameter are additive to the generated envelope signal.
- Maximum slew rate is approximately 1V/second.
Release: Manual decay time control for the generated envelope signal.
- Changes to this parameter are additive to the generated envelope signal.
- Maximum slew rate is approximately 1V/second.
Positive Envelope Output: Unipolar positive envelope output. Negative
Envelope Output: Unipolar negative envelope output
Comparator Threshold: Manual control that sets the threshold of the
comparator.
Comparator Gate Output: Gate output of comparator.
- If an input signal exceeds the Comparator Threshold, a gate signal is generated at the Comparator Gate Output.
Pedal Interfacing
Dual Footswitch Input: ¼” (6.35mm) input for the included Dual Footswitch or other compatible footswitch controllers.
-
A – Button: If the A – Button (left) of the Dual Footswitch is pressed, a trigger signal is generated at the A – Button Trigger Output.
-
A – Button Trigger Duration: Manual duration control of the trigger signal generated at the A – Button Trigger Output when the A – Button of the Dual Footswitch is pressed.
Trigger duration range is 5ms to 500ms. -
A – Button Trigger LED: LED indication of the signal present at the A – Button Trigger Output.
-
A – Button Gate Output: If the A – Button of the Dual Footswitch is pressed, a gate signal is generated at the A – Button Gate Output.
A gate signal will be held HIGH for as long as the A – Button of the Dual Footswitch is pressed. -
A – Button Gate LED: LED indication of the signal present at the A – Button Gate Output.
-
B – Button Gate Output: If the B – Button (right) of the Dual Footswitch is pressed, a gate signal is generated at the B – Button Gate Output.
A gate signal will be held HIGH for as long as the B – Button of the Dual Footswitch is pressed.
Latching Gate Button: Button that, when pressed, will generate a latching gate signal at the B – Button Gate Output.
- If a gate signal is already held HIGH at the B – Button Gate Output due to the pressing of the B – Button on the Dual Footswitch, pressing the Latching Gate Button will flip the state of the B – Button Gate Output, forcing the gate signal to pull LOW. Similarly, if a gate signal is already held HIGH at the B – Button Gate Output due to the state of the Latching Gate Button, pressing the B – Button of the Dual Footswitch will flip the state of the B – Button Gate Output, forcing the gate signal to pull LOW.
Patch Examples
Distorted Guitar Amp:
Summary: When the electric guitar signal is connected to làrachd, làrachd
acts as a preamplifier while tanh[3] acts as a distortion. 
Audio Path:
- Connect an electric guitar to the Stereo Line Input of làrachd.
- Set the Stereo Level knob to 4:00.
- Set the Source Toggle to its up position, allowing the Stereo Line Input signal to normal to the Enhance Input.
- Set the Enhance Level knob to its maximum position.
- Connect the Enhance Output to a channel of tanh[3].
- Set the level of tanh[3] to a desired position.
- Monitor from the output of tanh[3].
Guitar Controlled Synth Voice:
Summary: The electric guitar signal gets amplified and sent to the
envelope follower. The generated envelope signal then modulates a low-pass
filter and a VCA. 
Audio Path:
- Connect a desired waveform of an oscillator to the audio input of a low-pass filter.
- Connect the audio output of the filter to the audio input of a VCA.
- Monitor the audio output of the VCA.
- Set the fundamental frequency of the oscillator to a desired position.
- 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 its unity position.
Control Path:
- Connect an electric guitar to the Stereo Line Input of làrachd.
- Set the Stereo Level knob to 4:00.
- Set the Source Toggle to its up position, allowing the Stereo Line Input signal to normal to the Envelope Follower Input.
- Connect the Envelope Follower Output to a multiple.
- Connect one copy of the Envelope Follower Output signal to the FM input of the filter and set the corresponding CV attenuator to a desired position.
- Connect a second copy of the Envelope Follower Output signal to the CV input of the VCA and set the corresponding CV attenuator to a desired position.
- Set the Response Curve Switch to its left position, making the envelope signal linear.
- Set the Attack and Decay knobs to their minimum position.
Hands Free Recording:
Summary: The Dual Footswitch controls either both Record functions on
Lúbadh or the Capture and Strike functions of arbhar.
Lúbadh Control Path:
- Connect the Dual Footswitch to the Dual Footswitch Input of làrachd.
- Connect the A – Button Gate Output to the left Record Gate Input of Lúbadh.
- Connect the B – Button Gate Output to the right Record Gate Input of Lúbadh
arbhar Control Path:
- Connect the Dual Footswitch to the Dual Footswitch Input of làrachd.
- Connect the A – Button Gate Output to the Capture Input of arbhar.
- Connect the B – Button Gate Output to the Strike Input of arbhar.
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.