Systech - Harmonic Energizer

[D-Day]

Just finished building one on a Madbean 'Karate Shop' PCB. Added a volume control and the suggested by Grizzlydude 1.5u output cap on a switch with the other option being stock. Fun build, nice sound. I built it for an owner of an original so here in a few I get to see how he thinks it stacks up. Can't do a side by side as the original unit is now busted but the owner is a dog eared engineer who used it for lots of rock sessions over the past 20 years.

[D-Day]

Works like a charm! My buddy says it doesn't sound quite exactly the same but it definitely does the same job and he's just tickled pink. We hooked it up to a red knob Fender Concert and I noodled on my SG while he twiddled knobs. This thing is fun and awesome by itself but get a fuzz or a distortion in front of it and let the games begin! Thanks to Joe, Grizzly, Madbean and anybody else that contributed to my ability to give this gift to one of my greatest friends ever.

[terrapin]

Almost a year on and PurplePeopleEater's pcb layout (and Joe's original gut shots) have long gone. Anyone still have them and care to repost them? Pretty please?

[JOHNO]

Systech harmonic energizer.png

[jreeves47]

Some guts

[Nocentelli]

Got this on the breadboard at the moment, sounds good. I used a 2N5457 for the input buffer which works fine, and didn't bother with any of the power related circuitry other than the 10k/10k/10uF volateg divider.

I've also got a switch that puts either one or two pairs of antiparallel 1N4148s across the output opamp's inverting input and output, which makes the higher gain settings a bit smoother: The single pair just clips a bit earlier than two pairs. I'll probably use this when I box it up.

I have one question for anyone who understands this circuit: I'd like to use my EV-5 expression pedal for the frequency pot. It's a 10k, and I'm not at all sure what I'm doing, so I just tried reducing the 20k resistor that leads to the freq control opamp by a factor of 5 to match the pot value decrease. However, I just get squeals (through headphones - ouch). I'll have a go at altering those two 10uF caps, but I'm not sure if they should go up or down in value. Any ideas?

[Mbas974]

Are you using RnFR (page 5) schematic ?

[Nocentelli]

Yep

[grizzlytone]

Got this on the breadboard at the moment, sounds good. I used a 2N5457 for the input buffer which works fine, and didn't bother with any of the power related circuitry other than the 10k/10k/10uF volateg divider.

I've also got a switch that puts either one or two pairs of antiparallel 1N4148s across the output opamp's inverting input and output, which makes the higher gain settings a bit smoother: The single pair just clips a bit earlier than two pairs. I'll probably use this when I box it up.

I have one question for anyone who understands this circuit: I'd like to use my EV-5 expression pedal for the frequency pot. It's a 10k, and I'm not at all sure what I'm doing, so I just tried reducing the 20k resistor that leads to the freq control opamp by a factor of 5 to match the pot value decrease. However, I just get squeals (through headphones - ouch). I'll have a go at altering those two 10uF caps, but I'm not sure if they should go up or down in value. Any ideas?

Try increasing those 10uF caps with a factor of 5 (47uF), it might just work...

/MB

[aishabag23]

Here's a PCB layout for the Harmonic Energizer. You can board mount the pots or run wires, whichever. The PCB size is 3 inches x 1 3/4 inches, so it will easily fit in a Hammond 1590BB sized enclosure. I used a TL074 (as in Grizz' vero layout) instead of using 2 TL022 op amps. It just keeps things neater and the sound difference should be marginal at most. It should be correct (Eagle checks connections), but if you see any errors, please let me know.

I forgot to show the board connections on the bottom of the layout. The layout attached below has them marked.

Greetings,
Any chance you could link me to this? I can't seem to open the attachment (says it no longer exists).

Thank you!
Aisha

[roseblood11]

Does anybody know, how the additional switches in this version work? Would be great to include them.
https://youtu.be/lhNFPsbv2Lk

[Lani]

Thought I would add my layout here as well... Not verified yet but will build it in the next couple of days and let folks know.

[cniers13]

Lani, have you gotten it to work? I'm curious because I like the idea of adding a volume knob, instead of just the three knobs.

[snk]

Hello,
I have built it last week, and it sounds great.
I would like to add an expression pedal to control the frequency (with a switched closed jack tied to the freq pot), but my attempts failed : I tried with several expression/volume pedals (2 of them have a 50K pot, so it should match), but i'm getting only noise and squealing while moving the pedal... Would anyone have a clue how it should be done (or did anyone manage to make such a mod) ?

[Zokk]

Hello
as the Frequency pot is wired as a variable resistor you could use a vactrol/LDR in parallel + a limit resistor (to limit the max resistance of the vactrol/LDR).
Then with a TRS jack and a zener diode you send some voltage to your expression pedal (Ring), and the return (Tip) will go to a simple transistor LEd driver.
With some adjustements you may be able to have a functional control over this pot with a passive 20K expression pedal.
Example with a trick to change sweep direction in the expression pedal:

External Control.jpg

This circuit allows a classic CV input too, if you have some synths or arduino/PIC based sequencers...

[Zokk]

Sorry no "edit".
By the way the pot1 is the expression pedal's pot which is more or less the standard value, 20K/25K it's ok.

[snk]

Thank you very much, Zokk.
"Z1 8V2" is the vactrol, right ? I have some vactrols, but never used any so far... I guess it's time to begin
And "pot2" the pot on the circuit, right ?

This circuit allows a classic CV input too, if you have some synths or arduino/PIC based sequencers...

That's good to know : i'm not a guitarist, i'm a synth player

[plush]

"Z1 8V2" is the vactrol, right ?

Z1 8v2 is a 8.2 volt Zener Diode

[snk]

"Z1 8V2" is the vactrol, right ?

Z1 8v2 is a 8.2 volt Zener Diode

That was actually obvious

[Zokk]

No the vactrol and its driver are not shown.
A vactrol is a LED + an light dependant resistor (more light=less resistance), so you have to know what resistance values you need, here it's around 50Kohm, so you'll add a limit resistor in parallel with the LDR to avoid huge values when in the dark (ie around 1Mohm or more depending on your LDR).
If you use a VTLXXX you'll have to look at the datasheet to get theses values, if you use a DIY vactrol you can cheat and use a HiBrightness LED to reduce the LED current and still have a max brightness with a low resistance on the LDR side.
I mean 20mA only for one LED (from the VTL5C3 datasheet) is way too much for a pedal use.
I suggest the cheap GL5516 LDRs in pair with some flat head lo-power/hi-brite 5mm green LEDs (I had also good results with amber transparent LEDs), I can get less than 100ohm at 7mA with a +5V supply!

In my previous message you only have the interface which allows use an expression pedal with a send/return system to have a control voltage under your feet. Then you do what you want with this foot-controlled voltage
The idea with the zener is to make the voltage which goes to the expression pedal independant from your battery or PSU; you'll always have a steady 8.2V or maybe a bit less but this won't fluctuate.
So you can adjust precisely the max voltage with the trimmer before the LED driver.
Here is an example how to hook a basic driver to the send/return exp. pedal and your circuit (A, B, and the Freq/ pot are on your board):

External Control2.jpg

A good starting point for the drivers and synth abuses:
http://electro-music.com/forum/topic-49449.html