JunkTrunk envelope detector sensitivity

[LFlab]

Just built a Junk Trunk, which was a very pleasurable experience, I really like the style of layout, sensible spacing of components, very nice.
Limited wiring is also nice 

It works also, so that is good, but the envelope detector seems a bit too sensitive. Haven't played around with it very long, but I think attenuating the signal going into the envelope detector could help a bit. But it might very well be the components I used, I used a 3.6V zener rather than 3.9 and I selected a green LED with 2.1V forward voltage drop (according to a table, yellow is between 2.1 and 2.2), as my particular yellow LEDs were all around 1.8V Vf which was atypically low for a yellow LED. Can someone explain the relation of the zener voltage and forward voltage drop with respect to functioning of the current to the OTA's?

[madbean]

Just built a Junk Trunk, which was a very pleasurable experience, I really like the style of layout, sensible spacing of components, very nice.
Limited wiring is also nice 

It works also, so that is good, but the envelope detector seems a bit too sensitive. Haven't played around with it very long, but I think attenuating the signal going into the envelope detector could help a bit. But it might very well be the components I used, I used a 3.6V zener rather than 3.9 and I selected a green LED with 2.1V forward voltage drop (according to a table, yellow is between 2.1 and 2.2), as my particular yellow LEDs were all around 1.8V Vf which was atypically low for a yellow LED. Can someone explain the relation of the zener voltage and forward voltage drop with respect to functioning of the current to the OTA's?

Well too much sensitivity is probably an easier issue to work around rather than not enough. I agree it is super sensitive. The JT and esp. the JT with the Gas Tank together have to be dialed in. Some settings are magic and others are more "meh".

As far as your LED and Zener choice I wouldn't worry too much about it. This OTA filter design is voltage driven and that driver is designed to be as sensitive as it can to your dynamic input. Small deviations may have some impact but the choice of "YELLOW LED" and "3v9 ZENER" probably came directly from experimentation rather than some esoteric calculation or simulation.

Finer point, if you want to reduce the dynamic response a bit you probably only need to change the gain response to the envelope detector. There are several ways to do it and I don't know which is going to be the best but my suggestion would be to reduce the values of R18 and/or R25. You may want to socket. Try 220k for R18 and/or 10k for R25. This will reduce the envelope response you get from the circuit input. I would take this approach over changing the LED type or Zener value you've used.

[LFlab]

Thanks for the reply, I've also been contemplating lifting the 220k resistor, and adding a trimpot and hot glueing that to the pcb, to allow dialing in. Or, do it at the jumper for the envelope input jack (which I did not fit).