Adding an Envelope Follower to the Karate Shop.

[strungout]

Hey.

So, I have the Karate Shop (Systech Harmonic Energizer clone) on my breadboard and I'm trying to implement an envelope follower to drive an LED/photocell.



I went the simple way first, after reading this thread https://www.diystompboxes.com/smfforum/index.php?topic=122814.0 , the Nurse Quacky EF up to the range pot. I put its wiper to ground. I tapped the signal from Q1's Source. The sensitivity pot works wierdly. Only a very small portion of the rotation actually has any effect. But it works. The ripple is even more horrible than remember though XD Then again, I'm just a hacker. Anyway. At rest, the filter is in the open position. If I keep playing softly it stays open. If I hit the strings harder, it instantly (or so) goes into the closed position and then starts opening up. I kinda like it. But it's not exactly what I'm after.



I don't really know the LDR stats of my homemade vactrol. Think it's an 11M dark. I forgot to put it in a labeled bag...  I have some 50k-3M and 20k-1M LDRs to try, along with fiddling with the resistor value that replaces the 50k Frequency pot and goes in parallel with the LDR. I've noticed that from other ECF circuits. (Side note: Not fun to forget to turn off the amp before changing that resistor... when you have headphones on... loud, piercing high squeal... ouch). The goal is to get that total resistance going from, let's say 1-2 hundred ohms (or whatever I can get away with without squeal), to 50k. Am I right?

Next, I want to try the MXR Envelope Filter EF. I like it's response a lot. I have no idea where to put the LED though. Do I just tack it at the end, after the normal/reverse sweep section, with a current limiting resistor to ground? Vb?

http://www.generalguitargadgets.com/wp-content/uploads/ggg_mxr_envelope_filter_mods.pdf

Then there's the Quackmire (giggity), Duck Ranger, kipper4 (Rich Pyper)'s HammerTime EFs to try out. Anyone have a favorite EF to share? Any other insights?

I'll go back to messing with the thing now.

[Mark Hammer]

First, good on you for experimenting.
Second, I'm assuming you wish to tinker with the Frequency control of the Karate Shop.  Note that reducing the resistance of the Frequency pot moves the resonant frequency down, while increasing it moves the frequency higher.  If an LDR is placed in parallel with the Frequency pot, illuminating the LDR will reduce the combined parallel resistance.  That is, picking hard will send the pot+vactrol towards a lower resonant frequency.  If the Freq pot is already set for a low throaty peak, you may not actually hear the change, since sticking a second resistance in parallel with an already low resistance yields little parallel change.  Conversely, if you have tuned the Freq control higher, the default (minimally illuminated) value of the LDR may already bring the combined parallel value down to where resonant changes are only minimally audible.

For the LFO-swept one I made, I placed the LDR in series with the Freq pot.  When the LED goes brightest, there is no real audible change in resonant peak.  The LED has to go dark for that to shift.  And, because smallest pot resistance = lowest resonant frequency, adding resistance to that moves the peak upwards, then back down to the Frequency pot setting.

[strungout]

It's always fun to just try stuff. Though usually nothing really comes out of it. I had, if you remember, tinkered a lot with the Nurse Quacky and its EF when I first joined this community, and I got some interesting results from it. Like a more resonants peak with distortion and some rumbling envelope decay ripple. So, I wasn't in completely unknown territory.

Second, I'm assuming you wish to tinker with the Frequency control of the Karate Shop.  Note that reducing the resistance of the Frequency pot moves the resonant frequency down, while increasing it moves the frequency higher.  If an LDR is placed in parallel with the Frequency pot, illuminating the LDR will reduce the combined parallel resistance.  That is, picking hard will send the pot+vactrol towards a lower resonant frequency.

Yes, and duly noted. I understand why the filter behaves as I described. I'll put the LDR in series and hear what that does. If I understand correctly, the Frequency pot, then, will affect the sweep's 'travel' to the top frequency. Set to low frequency, it'll travel more than at higher frequencies.


In the meanwhile, I tried the MXR Envelope Filter EF and I can get the LED to light up (bright when grounded, dim when connected to Vb. But it's not responding to picking dynamics... And there's the fact that it takes at two 4069 to build it and four inverters are pretty much wasted... I think I'd better go with another EF.

Alright, I'll go play around some more!

[strungout]

Bah. Experimentation is fun, but it can often leads to frustration/confoosion for me, as per my lack of knowledge, obviously. I need to read up more, I guess.

I tried a bunch of EFs that could have been suitable... if I got them to work... and I couldn't. MXR Envelope Filter, Meat Sphere, Quackmire, HammerTime...  Either the led would light up and not respond to picking dynamics, or it didn't light up, but did when I approched a finger near the LED... kinda like a Dr Proxxi wah. (Wasn't that from Transmogrifox?) Thing is, they all work in their respective circuits. Just not with this one.

I have 2-3 more EFs to try... I might have to content myself with the Nurse Quacky EF... or get a stand alone expression pedal...