PCB - US$18
panel - US$20
These are AR or AD generators that will fire on a trigger or a gate, giving envelopes up to approx 25 seconds. A single gate to input 1 will fire all 3 envelopes, when nothing is plugged into inputs 2 & 3.
SMD chips and resistors, but a very easy build with minimal components.
Note - the current panel is white/gold
Build guide is HERE