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! 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. 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.
Additionally, the Boing!'s transistor-based input and output stages provide pleasing tonal variety (i.e.
overdrive) depending on the level of the Audio Input signal.
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.
These are but two 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!
