Boing! - Synthesizer SetonixSynth - Free user manual and instructions

Type de produit	Eurorack Synthesizer Module - Low Pass Gate
Marque	SetonixSynth
Modèle	Boing!
Hauteur	3U (128.5 mm)
Largeur	4 HP (20 mm)
Profondeur	25 mm (typical)
Poids	Approx. 100 g
Alimentation	+12V and -12V via 10-16 pin ribbon cable (reverse diode protected)
Courant consommé	+12V: 50 mA, -12V: 10 mA (estimated)
Fonctions principales	Discrete transistor LPG with 1/2 pole switch, Offset, Damping, CV input with attenuator, Hit! trigger input, Audio In/Out, Vactrol-based filter
Plage de tension d'entrée CV	±10V (bipolar accepted)
Plage de tension d'entrée audio	Up to 16Vpp (clipping above 10Vpp)
Réponse en fréquence	Low-pass, 6 dB/oct (1-order) or 12 dB/oct (2-order)
Entrées	1x Audio In (3.5mm TS), 1x CV In (attenuated), 1x Hit! trigger/gate
Sorties	1x Audio Out (3.5mm TS)
Contrôles	Offset knob, Damping knob, CV Atten knob, 1/2-Order switch
Matériaux	PCB, aluminium panel
Entretien et nettoyage	Wipe with a dry, lint-free cloth. Avoid moisture and cleaning solvents.
Sécurité	Connect power correctly (red stripe aligned with indicator). Do not operate with exposed circuitry. Keep away from liquids.
Pièces détachées et réparabilité	No user-serviceable parts. Contact SetonixSynth for repairs.
Informations générales	Designed and assembled by SetonixSynth. Manual copyright 2021.

Frequently Asked Questions - Boing! SetonixSynth

What is the Boing! Discrete Transistor Low Pass Gate?

The Boing! is a Eurorack module that combines discrete transistor amplification with a vactrol-based low-pass gate, offering classic distortion and filter characteristics.

How do I power the Boing! module?

Use a standard 10-16 pin Eurorack ribbon cable. Align the red stripe (-12V) with the white silkscreen indicator on the module's rear header. The module is reverse diode protected.

What is the difference between 1-Order and 2-Order modes?

1-Order uses a single LDR filter stage (6 dB/oct slope), while 2-Order uses two stages (12 dB/oct slope) for steeper filtering and more pronounced resonance.

How do I get a 'Buchla Bongo' sound?

Set Offset fully CCW, switch to 2-Order. Patch a sine/triangle VCO to Audio In, send a fast envelope to CV In and Hit! simultaneously. Adjust Damping for harmonics.

What voltage should the Hit! trigger be?

Early builds require +10V for reliable pinging; modules post-October 2021 work with +5V gates or triggers.

Can I use bipolar CV?

Yes, negative CV will influence the control LEDs in combination with the Offset knob, allowing inverted modulation.

Why is my audio distorting?

The Boing!'s JFET amplifiers clip on inputs above 10Vpp. For cleaner sounds, attenuate the input signal externally and amplify the output.

How do I achieve Vactrol Compression?

Set Offset full CW, Damping full CCW, switch to 2-Order. Send audio to Audio In, an envelope follower's inverted output to CV In, and adjust CV Atten for compression amount.

What is the function of the Damping knob?

Damping introduces a phase-inverted signal to the first filter stage, altering the timbre by taming or enhancing harmonics.

Is the Boing! compatible with other Eurorack cases?

Yes, it follows the Eurorack standard with +12V/-12V power. Ensure sufficient current capacity (approx. 50mA +12V, 10mA -12V).

USER MANUAL Boing! SetonixSynth

Boing! Discrete Transistor Low Pass Gate User's Manual

Copyright 2021 SetonixSynth. All rights reserved.

Updated November 2021

Hello and thank you for using the Boing! Discrete Transistor Low Pass Gate. We hope you will find its tones most pleasing!

1. Connecting your Boing!

Use a typical 10-16-pin Eurorack ribbon power cable to connect the rear header of your Boing! to your Eurorack case's power bus. The -12V (red stripe) side of the ribbon cable must be aligned with the white silkscreen indicator stripe for proper use. This module is reverse diode protected, but it is still not recommended that you plug it in backwards to see what happens.

2. Theory of Operation

The Boing! Discrete Transistor LPG was conceived and designed with two things in mind: we loved the sound of discrete transistor gain stages such as those found in the Moog CP3 and Buchla Model 106 mixers, and we also loved the sound of simple passive LPG modules such as the PassiVac and Meng Qi DPLPG. Why not combine them?

Well, there are a few reasons! Given the advent and development of op-amps and OTA's, transistors offer a less precise and linear way to provide amplification or process Control Voltage, and Low Pass Gates process the frequency spectrum less unevenly (low frequency will always pass through more than high) than a modern “clean” amplifier. These circuits also operate between +12V and Ground, which is half the headroom of an op-amp powered with a bipolar supply. If the amplified signal exceeds about +10V at any stage, clipping will occur. Vactrols, or in this case LEDs facing Light-Dependent-Resistors, have a distinct “lag” behind their controlling signal.

However, the ear hears what it likes, and it likes distortion, Vactrol lag, and the sound of filters opening and closing completely. Together with an inverted feedback loop which can tame some of the wilder harmonics introduced by the various stages, these elements offer new ways to process sound, distinct from other Low Pass Gate designs, and can consistently offer up new and exciting sounds each time it's patched.

The Boing! operates like a typical Low Pass Filter in most regards: it has one Audio Input and one Audio Output, and the signal present at the Output will represent a modified version of the Input. The knob labeled "Offset," Control Voltage present at the "CV In" jack (attenuated via the "CV Atten" knob), and Triggers or Gates sent to the jack labeled "Hit!" will all influence the filter's cutoff frequency. Early builds of this module will require a +10V gate or trigger to significantly "ping" the LED, while any built post-October 2021 will work well with +5V.

Negative control voltage can be used to influence the control LEDs as well in combination with the Offset knob. Finally, the knob labeled "Damping" introduces a phase-inverted signal to the first filter stage which changes the filter's timbre.

In the case of the Boing!, filtration is being done by one or two Light-Dependent Resistors configured as Low Pass Filters, depending on the position of the Switch: "1-Order" indicates one stage of Low Pass Filter, while "2-Order" indicates two stages. The LDRs determining the cutoff of each stage are controlled

by optically coupled LEDs which in turn are controlled by the "CV" input, "Hit!" trigger input, and "Offset" knob, forming what is commonly known as a Vactrol. As is characteristic of LDRs, this filter's response to CV relative to its frequency sweep will be less linear than a "typical" active filter, though in the case of the Boing! measures have been taken to improve this over regular passive LPGs.

A note on distortion in the Boing!: the sonic characteristics of this module are heavily influenced by the two JFET transistor-based amplification circuits on the input and output of the filter stages. These single-supply amplifiers are significantly less “clean” than more modern op-amp-based solutions. They will introduce significant clipping to a traditional Eurorack-level input, i.e. 10Vpp, and break up entirely as the input level approaches approximately 16Vpp. Users wishing to achieve anything close to a “clean” sound with the Boing! will need to attenuate the input signal and amplify the output signal using external module(s).

3. Patch Ideas

"Buchla Bongo"

Turn Offset fully CCW and set switch to "2-Order." Patch a sine or triangle wave VCO into the Audio In and send a short, fast-attack envelope to the CV Input and trigger input simultaneously. Adjust Damping to modify harmonic level. Optional: if your VCO has a hard-sync, send your envelope or a synced trigger to the Sync input to reset the phase with each Bongo hit.

"Vactrol Compression"

Turn Offset fully CW, Feedback fully CCW and set switch to "2-Order." Patch audio signal into Audio In and an envelope follower. Invert output of envelope follower using a CV processor and patch to "CV In" and use CV Atten to adjust amount of compression/ducking.

Patch an oscillator into the Audio Input and monitor the output. Send a repeating trigger or trigger pattern into the "Hit!" input and feed an LFO or sample and hold into the CV input. (This works especially well with bipolar CV input.) Attenuate the CV input and adjust the Offset to taste.

These are but three ideas, and many other delightful sounds can also be achieved through a thorough exploration of the module. We hope that the Boing! can help to bridge the gap between the delightful immediacy of a passive Low Pass Gate and the expanded tonal possibilities of more sophisticated filters. Enjoy!