Pons Asinorum#

Small four-channel voltage-controlled linear envelope generator and LFO


Pons Asinorum is a compact four-channel multimode envelope generator and LFO with voltage control. Pons Asinorum has three different envelope shapes, CV over cycle length, and a unique single-encoder control scheme that makes adjusting multiple channels mid-performance easy. Channels can be set separately to envelope mode or to cycle in LFO mode, giving Pons Asinorum maximal flexibility in a minimal footprint.

  • Type: Quad Envelope/LFO
  • Size: 6HP Eurorack
  • Depth: .8 inch
  • Power: 2x5 Eurorack
  • +12 V: 60 mA
  • -12 V: 50 mA


Pons -- from Latin: "Bridge"

Asinorum -- from Latin "Donkey"

"Bridge of Asses"

Also used as a name for proposition 5 from Book 1 of Euclid's Elements.

Input & output voltages#

CV inputs respond to 0 V to 5 V.

Envelopes will trigger on a rising edge of about 3 V.

Output voltage is 0 V to 5 V.


Power connector

To power your Noise Engineering module, turn off your case. Plug one end of your ribbon cable into your power board so that the red stripe on the ribbon cable is aligned to the side that says -12 V and each pin on the power header is plugged into the connector on the ribbon. Make sure no pins are overhanging the connector! If they are, unplug it and realign.

Line up the red stripe on the ribbon cable so that it matches the white stripe and/or -12 V indication on the board and plug in the connector.

Screw your module into your case before powering on the module. You risk bumping the module's PCB against something metallic and damaging it if it's not properly secured when powered on.

You should be good to go if you followed these instructions. Now go make some noise!

A final note. Some modules have other headers -- they may have a different number of pins or may say "not power". In general, unless a manual tells you otherwise, do not connect those to power.


Illustration of Pons Asinorum's interface

Channel select 1-4 buttons
Enable or disable channels for editing. LEDs for selected channels will display as red or purple, depending on cycle length; deselected channels will be unlit (indicating minimum length) or blue.
Length encoder
Adjusts the cycle length of selected channels. Pressing the encoder resets selected channels to their minimum length. Tap again to undo the reset.
Hit button
Tap to trigger selected channels in envelope mode or to reset phase in LFO mode. Hold down Hit for two seconds to activate/deactivate LFO mode on selected channels.
Mode switch
Switches all four channels between ramp up, up/down, and ramp down modes.
CV inputs 1-4
Change each channel's cycle length.
Trigger inputs 1-4
Triggers an envelope or resets LFO phase, depending on channel mode. Trigger ins are internally circularly normalled: sending a trigger to any channel with no other triggers patched triggers all four envelopes. Patch another trigger in to break normalization past that point.
Outputs 1-4
Channel outputs.
Behavior settings
Sample and Hold: Holding Hit down on power up changes CV response from continuous to sample and hold. On startup, after initial LED flashing, all four channel LEDs will flash blue to indicate sample and hold mode or red for continuous mode.
Short/long response
Holding the encoder down for about 2 seconds and pressing a channel button changes the CV response range of that channel (blue for short, red for long).
LFO Mode
Hold down Hit for two seconds to activate/deactivate LFO mode on selected channels.
A note on cycle length
Using the encoder, Pons Asinorum's envelopes can range in length from 2.5ms to 9 seconds. With CV applied, Pons Asinoarum's envelopes can be up to 95 seconds in short mode and 320 seconds in long mode.

Patch tutorial#

Basic patch

Patch a trigger or gate into Channel 1's trigger in. Patch Channel 1's output to something in your system that would enjoy an envelope. Select Channel 1 and use the mode switch and encoder to change the envelope length and type. Unpatch the trigger in and hold down Hit to switch to an LFO, and again adjust cycle time and shape to best suit your patch.

Variety is the spice of life, and different types of modulation are the spice of eurorack. Set each channel to what you need: envelope mode or LFO mode. If you only need one envelope, you can still use three other channels as separate LFOs. With four channels of CV-controlled modulation, there are many self-modulated patches that can be created with a little creativity. For instance...

Quadrature LFO
Set each channel to envelope mode with a reasonably long cycle time. Set the mode switch to the middle up/down position. Mult Channel 1's output to a CV destination in your system, and to Channel 2's trigger in. Do the same for Channels 2/3, 3/4, and 4/1. Deselect all but one envelope, and trigger it with Hit. The envelopes will now cycle 90 degrees out of phase from each other, much like a quadrature LFO.

Design notes#

Like so many of our modules, Pons Asinorum has had several incarnations. Sky King (Kittyspit) originally suggested we make a small dual decay module. For years, we worked on that and it was just never compelling by itself. It languished. When NE friend Dave Driggers mentioned the name of his band, Pons Asinorum, something clicked and we realized what we needed to do: expand the functionality beyond just decay. It's the first module we've done where the function was inspired by the name (loosely, yes). We added attack and attack/decay to the module and we were excited again! Getting near-final hardware coincided with us finding Markus Cancilla as the first NE employee and he made so many good suggestions that substantially improved the final product you now hold.


We will repair or replace (at our discretion) any product that we manufactured as long as we are in business and are able to get the parts to do so. We aim to support modules that have been discontinued for as long as possible. This warranty does not apply to normal wear and tear, including art/panel wear, or any products that have been modified, abused, or misused. Our warranty is limited to manufacturing defects.

Warranty repairs/replacements are free. Repairs due to user modification or other damage are charged at an affordable rate. Customers are responsible for the cost of shipping to Noise Engineering for repair.

All returns must be coordinated through Noise Engineering; returns without a Return Authorization will be refused and returned to sender.

Please contact us if you think one of your modules needs a repair.

Special thanks#

  • Skyler King
  • Dave Driggers