Envelope Generator

AD/AR envelope with secondary envelope and hold function

This is a simple AD or AR envelope generator with a handful of novel extras tacked on.
There are two main envelopes with manual control over rise and fall times (sorry, no voltage-controlled rise or fall), two slightly more interesting envelopes derived from the first two, and two gate outputs.
Both envelopes have a basic RC charge/discharge curve with approx. 1ms to 1600ms rise time, and 30ms to 3000ms fall time. (If doing DIY you can try 1M pots for longer maximum rise and fall times and/or increase the value of C1 and C2)

Envelope 1 is controlled by the GATE and TRIG inputs.

Envelope 2 is triggered by the completion of envelope 1's attack/rise stage.

Output 3 follows whichever of 1 and 2 is higher. It can make twin-peaked envelope shapes.

The fourth envelope, 1-2, is a bipolar output and will swing negative when output 2 is greater than 1.
Depending on knob settings this output will rise to approx 8V, fall to approx -8V, then return to 0V.

Q is a gate that is high during envelope 2 attack stage and not-Q is a gate that goes high when 2 has finished its attack stage. The Attack times of the envelopes 1 and 2 make these outputs into a sort of 'gate delay'. Usually these two are the opposite state to each other but may both be high at the same time when using the GATE input.

The TRIG input provides Attack/Decay behaviour and accepts any voltage that crosses about half a volt. On the rising edge of a signal applied to TRIG the first envelope is set to Attack/rise. When it reaches the top (approx 8V) envelope 1 is set to Decay/fall and envelope 2 is set to Attack/rise. With nothing plugged into TRIG or EN the cycle will loop once 1 and 2 are both finished.

EN stands for 'Trigger Enable' and is held high with nothing plugged in. Patching a signal into EN means signals applied to TRIG will only trigger the envelope when the signal applied to EN is also high. Rising edges on EN will also retrigger a finished envelope while the signal on TRIG is high.
Think of TRIG and EN as a logic AND-gate for triggering the envelopes.

The GATE input provides Attack/Release behaviour.
On the rising edge of the input signal envelope 1 will be set to Attack/rise and will only reset to Release/fall when the input goes low. Envelope 2 will still trigger when 1 completes the attack stage but will also stay high until the signal on GATE is low.
Triggering is ignored when GATE is high and can resume when low.
Using the GATE input creates envelopes approx half a volt higher than the peaks of triggered envelopes.
Envelope 2 won't be triggered if GATE goes low before 1 completes its attack stage.
To use the GATE input by itself you'll need to patch 0V in to TRIG and/or EN (patching them into each other will work) to disable looping/self triggering.

The HOLD input and toggle switch halt the charging and discharging of C1 and C2, freezing all outputs where they currently are.
With the switch down a gate signal applied to HOLD will freeze all outputs.
Setting the toggle switch up inverts the logic of the input signal so all outputs are frozen when the HOLD input drops low.
The switch works as a manual hold with nothing plugged into the HOLD jack.
The trigger/gate circuits still try to operate when the outputs are frozen so an envelope that was falling when it was frozen may start rising when it is unfrozen.
The frozen envelopes are pretty stable for a minute or so but will eventually drift due to leakages in the circuit components.

The graphic on the panel is an example of the four envelope outputs completing one triggered cycle.

8hp +12V: 15mA -12V: 5mA

https://isaacbeers.square.site/product/envelope-generator/17