Author Topic: Presenting the Qi-Gon : Envelope Filter/ Envelope Controlled Auto-Wah/Tremolo  (Read 10980 times)

0 Members and 1 Guest are viewing this topic.


I don't want to impose. But do to my low IQ I would really appreciate if you could put out a complete schematic.
And maybe some pics of the LDR/LED setup.
My special educator says that pictures or good for me! 

I have no access to my files right now but hope this will bring you further.


This is the coolest thing I've seen today!  I have only one suggestion: please show us your layout!  I might have to build this...   ;D
there ya go :-)

Cool! Thanks!
Ohm's Law - much like Coles Law, but with less cabbage...


This is smart.  A little busy to be a stopbox  :icon_lol: but definitely smart.

I guess by busy that you mean the too many knobs ... i really wanted to keep it to the essential but it's so hard with an envelope type of circuit. Either you settle for one sound and try to make it as good and consistent as possible or you go the opposite route but there are so many variables ... and so many possible sounds ... i could easily have doubled the amount of knobs :-)

I guess it's one of those pedals that you have to spend some time with. Once you get to know it, it's easy to dial in the sounds you want quickly.

Mark Hammer

Well, you kept it a lot simpler than this thing!

But I know what you mean.  Swept filters have a tendency to invite more and more features.  I'm sure somewhere out there is someone fiddling around with linear vs exponential sweeps, variable slope, auto-panned output, and any of a million things one can use.

Yesterday, I finally got an expression pedal set up to use with my Line 6 M5, and the unit allows for manipulation of up to 5 parameters at once via movement of a single expression pedal.  Let me tell you (aklthough clearly I don't need to), it is VERY easy to get carried away with control features on a simple swept filter!  :icon_lol:

While I have filter afficionados' attention, have any of you ever worked with the Mike Biegel meisterstucke EHX Bi-Filter?  Just curious as to what that's like.


I must have missed this in January and discovered it yesterday - nice work. I particulalry like the tremolo function. It's very clever.

I found this as I have been playing with an LFO-controlled state variable filter as of late. Mine has crude envelope control of the LFO speed and I stumbled upon this looking for other examples.
One thing you mght want to consider addding is a notch filter, which can give quite a convincing phaser effect. You can do this by tappling the (+) input of U1B or by adding the LP and HP. I think you have a spare splot on your rotary switch that could accomodate this without too much difficulty.
I'm a refugee of the great dropbox purge of '17.
Project details (schematics, layouts, etc) are slowly being added here:


good ideas !!

I was going to design and build an envelope controlled phaser/vibe with the same principle as this one, but I hardly get any time to work on pedals these days so this idea could be a quick fix for a phasey tone.

I had read that you could create a notch filter but not quite understood how to implement it. Do I just connect the outputs of LP and HP together and do I need some DC blocking Caps between them? Maybe someone knows an example where that arrangement would be used. Some sound examples would be great too :-)


It seems that you can get the notched filter by directly tapping the (+) input of the first op-amp in the filter - your U1B. I have only done that straight into an op-amp buffer and this may not work too well with you mix pot. Instead, I would suggest you mix the LP and HP by connecting e.g. a 10k resistor from each of the outputs: LP -10k - notch - 10k - BP. As a bonus, you should be able to do right on the rotary switch so it will not require any extra wiring.

Edit: fixed typo
« Last Edit: March 21, 2013, 01:48:11 PM by samhay »
I'm a refugee of the great dropbox purge of '17.
Project details (schematics, layouts, etc) are slowly being added here:


I will definitely try that out :-)