Systech Harmonic Energizer - Mods/Analysis

[pinkjimiphoton]

dude,
you can do it like this too if you're having problems. make sure your expression pedal has the same value pot as the pot you're replacing. you may NOT have to worry with some circuits, depending on the useable sweep of the pot being used.

simply do this

take one of them insulated plastic enclosed jacks, like you see in a crybaby. you want a switching jack.

connect the wire from pin one of your pot to ground on the switch side of the jack. pin two to the center conductor/sleeve of the jack
connect pin 3 to the tip of the jack. by using the plastic jack, you can isolate it from ground, and get away with using a short trs cable.

wire the pot to the unswitched side the same way...  then when ya plug your expression pedal in, nothing will short, and you'll replace the pot in the pedal with the one in the exp.

doesn't always work, but a lot of times, it will. i've done it with phasers n stuff, dunno if it will work well with this circuit. but if you haven't tried it that way, maybe it will work.

rock on!

[snk]

Hi,

Thank you for your tip !

I tried to use a TRS jack with the sleeve (ground) disconnected on the pedal's side : it works, but the effect self-oscillate quite easily (the Harmonic Energizer is quite wild, but here it is meta-über wild, much prone to self-oscillation than when i only use the knobs). Also, i noticed that the filter range is quite different when using the pedal or when using the knob.
The pedal is a Moog expression pedal, so its internal pot should have the same value (50K) than the  Harmonic Energizer.

I will try with your wiring tomorrow

One thing I noticed is that on the layout i used, the FREQ lugs 2&3 are wired together, so it maye have an influence.

[pinkjimiphoton]

yeah, in that case you may find it works better pushed in just one click maybe. if the knob ya wanna control by treadle has two pins tied together, that makes it easy. you can use a hunk of 2 conductor and shield for the whole mess.
just make sure the shielding is connected on ONE side only use the tip connection for lugs 2 and 3 and the ring connection for lug 1, and don't connect the shield to the exp pedal side, but DO connect the pedal shield to the actual pedal so its grounded. that way, the shield is "telescoped" over the length of the cable and hopefully will prevent ground loops.
but in all honesty, there's a better way to do it... there has to be. with a high gain, high impedance signal, its gonna be noisy and probably oscillate no matter what you do.
so maybe the secret would be to put a small led/ldr combo or something. there's gotta be a tricky way to do it and make it work that i'm just not getting.
good luck, keep us posted bro!

[Mark Hammer]

I will put in a good word for photocells.

When I learned that the Line 6 expression-pedal standard was simply a 0-19k variable resistance to ground, I thought "Hey, I can do that with a photocell!".  I hooked up a long piece of 2-conductor wire to a phone plug, attached the other end to a suitable photocell attached to the top of my guitar with double-sided tape, and plugged the thing into my Line 6 M5 pedal.  Covering and uncovering the photocell allowed me to control things with my pinky finger, which has a different "feel" than what you can do with your foot.  And of course, the nice thing about the M5, and similar devices is that one expression pedal can control multiple parameters, and they can be be programmed to go in whatever direction you want (increase OR decrease) as the photocell resistance goes low OR high.  The caveat is that you need a reliable source of light such that covering up the photocell with your finger actually accomplishes something.

Of course that expression control is NOT part of the audio path.  In the case of the Harmonic Energizer, although it would be a simple matter to wire up a photocell in parallel with the Frequency pot, adjust the frequency pot to maximum resistance, and use the photocell to reduce that resistance by exposing it to light, such a cable would be carrying audio, and be subject to noise sources, in a way that is not true with my M5.  HOWEVER, that does not stop you from mounting a photocell on the top surface of the pedal, where you can easily get to it with your foot, and use it like a controller.

Something to ponder.

[snk]

Thank you both for your help.
I will try with different wiring, but the more i read about it, the more it seems that LDR is the way to go 
As the wiring is already done into an enclosure, and as i am already enjoying the sound of the Energizer, i will see if i find an easy way to use an expression pedal with a LDR.
Else, it sounds great already as it is

[pinkjimiphoton]

maybe you can do something like this. wire up a guitar cord from the pedal treadle's input and wiper like normal, but back at the pedal put in a small daughterboard with an led and a photocell. put the photcell in parallel with the control like mark said,  but use the expression pedal to control not the audio function, but the juice to the led. all the way up, you have whats set on the control. but when ya move the treadle, you're not adjusting any audio, just a control voltage to the led. as the led lights up, it will change the resistance of the ldr in parallel with the pot, and thereby sweep the control for you.

i thiMk it would work, never tried it but it seems feasible. you could control pretty much any pot the same way, i'd imagine.

since there's no physical connection to the audio, there should be zero noise pollution or oscillation from longish cable runs, too.

and if ya put limiting trimmers, you can dial in a sweet spot from full off to full on of the led. you'd likely have to experiment with the value of the photocells, but i'm betting it will work and do what ya want it to,
and hell, if it does,
you me and mark may have just figured out a cool way to remotely control effects pretty much universally.  i mean, two trimmers an led and an ldr should fit into almost anything.

if ya try it, let us know. i may try n cobble something together myself!!