Museum of Lost Effects:
The Systech Harmonic Energizer


A homely clone cowers in the shadow of a ramshackle original.

Okay, here’s an old weirdo I’ve been meaning to write about for ages. The Systech Harmonic Energizer is an ultra-rare filter/distortion effect from the ’70s that takes the fuzz-wah formula in some interesting directions. Its signature is edgy, ultra-resonant filter sounds. You’re most likely to have heard it generating Frank Zappa’s nasal midrange squawk, but it does lots of other abrasive tricks too. I used this one on Tom Waits’s “All Stripped Down,” and on “Jets” by Action Plus.

The S.H.E. doesn’t do pretty. Most of its sounds are so strongly flavored, they’re hard to use as a primary tones. But it’s great for things like clanky percussive accents, or walloping low-frequency assaults.

But let’s talk later. First the video:

This is one of the few pedals accorded “Hen’s Tooth” status in Analog Man’s Guide to Vintage Effects, a cool reference book that seems to be getting as hard to find as — well, Systech Harmonic Energizers. Author Tom “Analog Man” Hughes tracked down Greg Hochman, who was the president of Systech back in the ’70s. Hochman said:

We did a custom preamp for a guitar that Greg Lake had. We were in Kalamazoo, where Gibson was….Ritchie Walborn had designed it; others asked us to build one for them. It eventually became what we called the Harmonic Energizer. It was a variable-state filter, which was kind of high-tech at the time, and it got a pretty good following from Joe Walsh to Jan Hammer….It allowed you to dial in up the Q of the filter, and by changing the frequency of the filter, you actually had the ability to choose what key you were going to have sustain and feed back. The thing actually had 55dB of gain when you got it up to a high-Q filter, so it didn’t allow you to be subtle onstage. It was dangerous, but it had a unique sound to it.

“Q” is another word for bandwidth, and the ability to dial in narrow bandwidths at high gain is what makes the S.H.E. so “dangerous” and interesting. But I have to admit I’ve never gotten close to choosing feedback frequencies by key as Hochman describes. That makes it sound like a refined musical instrument. But it’s really a nasty and unpredictable squawk machine. (Not that that’s a bad thing.)

A couple of years ago we dissected my S.H.E. over at, my fave stompbox group, which generated this long and interesting thread. (You might have to register to read it, but you should anyway — F.S.O. is a great little community.) I wound up with a clone that sounds a little better than the original, though it would probably be an even match if I weren’t too lazy to clean out all dirty pots and loose jack on the original.

A reference book worth owning — of you can find a copy!

A reference worth owning — If you can find one!

The S.H.E. has a deceiptively simple set of three controls: gain, filter cutoff frequency, and filter bandwidth. At moderate settings, it yields an assortment of stationary wah sounds. But you can also dial in ultra-narrow, ultra-resonant filtering beyond the range of most wahs. And these edgy filters burst into overdrive in weird, unpredictable ways. User beware.

It’s easy to build or buy a clone. Madbean, one of the participants in that original freestompoxes thread, sells a clone PCB called the Karate Shop, with a project PDF here. (I love the fact that Madbean includes schematics and parts lists for all his project — the info’s there even if you don’t purchase any of his PCBS.) A completed Karate Shop will sound pretty much the same as the pedal in my video. Several other boutique builders offer pre-built clones, including Godlyke’s Triskelion, which Dweezil Zappa endorses. (The website says it’s out of production, but that they’re doing a 2013 update.

But I’m less interested in clones than improving/updating the circuit. I’d like to tweak the filter response, and I’d like to try it with a more inspiring distortion stage, maybe something germanium-based. Though I’m not sure whether it would be cooler to offer more filter options (filter types other than low-pass, for example), or adhere to the minimalist three-knob format.

Hmm — could it be time for a group collaboration?

59 comments to Museum of Lost Effects:
The Systech Harmonic Energizer

  • Derick

    How many pedals do you own?!?

  • jeremy

    ah, but have you made yourself a Project WEM fuzzbox yet? 🙂

  • Scott Riggi

    Joe….you are amazing….but you already know that….:)…Great post as always!…You have no idea how much I enjoy this stuff…Your work is greatly appreciated! Great to see peoples gifts in action. Happy Holidays!

  • Digital Larry

    Joe, you need to do a looped version of “Po-jama People”, which used the SHE along with a Pignose Amp (I just learned, and I thought I knew all things Zappa).

    This is what I would call a “state-variable” filter, from which you can get high-pass, low-pass, and band-pass at the same time. It has a few extra components compared to this one:

    All second-order state variable filters are going to sound pretty much alike when they are linear (not clipping). If you really put 54 dB of gain into your signal you’re probably going to get clipping and then it will depend on your gain elements. Op amps are not generally known for a pleasing overload characteristic. But you could put clipping diodes in the circuit to help suppress that, which I admit I’m warming up to as a concept. You can also tweak with the ranges of the controls.

    You can always put some other kind of boost/cut before or after this stage. I’d like to make a programmable version with 4 settings and maybe even two filter banks.

  • Digital Larry

    For chuckles I would make one of these with sockets for the op amps. Then I’d try TL072, LF353, and NE5532. The first two are JFET-input op amps with bipolar outputs. The NE5532 has a bipolar input, but has less than 1/3 the noise voltage of the other two. It might make for a quieter system. Or it might not work at all (doubtful)!

    • joe

      Yeah, and I’d add the OPA2134 to that list.

      • Digital Larry

        I wasn’t familiar with the OPA2134 (the others have been around for 20 years), but yes it seems like it has low input noise (5.1 nanovolts per root Hertz, yes that’s really how you say it).

        Also it has a very well controlled overload characteristic and doesn’t slip into “output phase reversal”. See figures 22, 24, and 25 of the spec sheet:

        Also check out figure 13 to see how THD + N (distortion + noise) change with level. Everything’s going along fine until WHAM!

        A more visual description of op amp output phase reversal can be seen here:

        [Note to self – capitalize on output phase reversal somehow…]

        I’m not sure what the TL072 is doing under extreme overload in this circuit though… have to check it out on a scope.

        What I’d try, in order, would be:

        1) Try a different op amp, like the OPA2134.

        2) Put a series resistor + back to back diodes on each filter op-amp’s output to smooth out the clipping behavior. I was also thinking about using Zener diodes to increase the voltage swing before clipping occurs.

        3) Increase the supply voltage to the filter section to +/- 15 to give it better headroom.

        4) Put a compressor or limiter circuit around the filter to dynamically adjust the filter’s input level to avoid clipping (by the filter, that is). This would be mutually exclusive to suggestion #2. Here’s a chip that purports to do a good limiter:

        5) I was trying to get some info or design insight into Moog filters as it seems these have been designed for overdrive since day 1. Didn’t find any schematics, just vague descriptions.

        • joe

          It’s kind of remarkable how different two ICs can sound. The OPA2134 has the same pinout as the TL72 and so forth, but is relatively hi-fi (and relatively expensive) in guitar effects. It isn’t always my favorite choice for distortion effects (though in general, I’m not very interested in IC-based distortion effects like Screamers and such). But it almost always gorgeous in modulation effects and in clean boosts. I’ve had real nice results combining a trashy germanium distortion stage with a relatively pristine OPA2134 booster.

          As always, my comments are 100% empirical — I can’t begin to explain WHY these ICs sound different. I’m just passing along what I hear. 🙂

          • Digital Larry

            Over at forum, I found a guy’s design for a “diode compressing op-amp”. This is a small discrete circuit that would take the place of an op amp chip.


            Supposedly this design keeps the output from slamming unceremoniously into the rails, at the expense of some soft clipping.

            One guy even says he uses Ge diodes to get that Germanium sound.

            Now this is going to be pretty complicated because if you did all 3 or 4 op-amp stages in the state variable filter this way, that’s getting pretty high up in the parts count for point to point wiring.

            I may give it a try on a breadboard, because I’m a little skeptical that the inherent tone of this SHE device can be preserved if the filter is kept clean and the distortion is done pre/post.

  • Wow. I think I’ve just fallen in love!!

  • Digital Larry

    Just keep in mind that the distortion in this circuit is being created by the op-amps. The Karate Shop schematic shows a FET front end arranged as a source follower – it’s just a buffer.

    So, changing the distortion sound may be a bit trickier than putting a fuzz front end on it. I have no doubt that this will change the sound, but there is still going to be significant contribution from the op-amps in the filter section.

    • joe

      Thanks for the info, Larry. I built my clone before I had any inkling of how the circuit worked, whereas now I have a vague inkling of an inkling. The fact that the distortion is created in an op amp probably explains why I don’t love the distortion sound.

      I’m really looking forward to experimenting with this!

      • Digital Larry

        Where there’s a will, there’s a way!

        You can avoid clipping in the filter by reducing the signal level going into it by an amount corresponding to the filter gain and amount of peaking cause by the “Q” setting.

        Just a pedantic note here… Q is inversely proportional to bandwidth. I.e. as Q goes up, bandwidth goes down and vice versa.

        It may be possible to keep the filter from distorting automatically by including a compressor or limiter type circuit, activated by the filter’s output level, but controlling the filter’s input level. This may require a variable gain element with a pretty wide control range. I’m removing my foil hat to put on my thinking cap….

  • Cool demo of a cool device Joe (as always, it would seem). Just this morning I was musing that you were due for a ‘museum’ post, et voila! It’s surprising that more folks haven’t tackled this unique corner of the pedal universe; its a genius tool for multitrack recording. How many times have you radically eq’d a part to fit it into a mix?

    • joe

      Well, I haven’t used this particular gizmo on all that many sessions, but the “method” here — looking for parts that fit into an uncrowded niche of the tone spectrum — has been a cornerstone of almost all my session work. It’s especially true when you’re trying to add guitars to a song that’s already fairly well developed, with lots of parts already in place. You know — like almost EVERYTHING we get called to play on in our home studio era. Often, the fat, full tones we love hearing at home just don’t work in context.

      The other big part of the equation is rhythmic — finding segments of a bar or phrase when there’s a lull in the action. Hopefully, the process is a little more sophisticated than noodling around every time the singer takes a breath. But I often force myself to stop playing, listen for a promising spot, and then concoct a part that sits there, even if it doesn’t feel 100% natural at first.

      Which isn’t to say that a lot of my demos and such don’t have parts walking all over each other. It’s hard to resist coming down on the downbeat sometimes. Yeah, it’s important to do as Boosty preaches and “get on the one,” but that CAN be too much of a good thing. 😉

  • 50FC

    Hey it reminds me of the Maestro Parametric Filter, you know that one ?

  • Oinkus

    Saw a Dweezil video about the Triskelion, think he has 3 of them in his chain and this is where it started so very cool!Those run $350 , I am guessing building one is much cheaper? Nice sounds ! Some great depth there just hard to find a place to place it.

    • joe

      Well, I’m not going to cast stones about overpriced effects, ’cause my stuff is expensive too (when I, like, have the time to actually make and sell any of it). But I’m guessing about $40 in parts, and not a very difficult build.

  • mwseniff

    Great demo as usual. “All Stripped Down” is a fave of mine (I’ve been a Waits fan since his solo warmup act for Zappa in the 70’s). Personally I think this pedal would be the bomb mounted in a wah shell so the cut-off frequency could be controlled by foot action (maybe even a dual axis wah so the width could be controlled as well). It might also be cool if you could modulate cut-off/bandwidth/gain with external LFOs. Of course that would give you some out of control sounds but I dig having to wrestle my FX for control of the sound at times (but heck I am a musical weirdo after all). I would also like to have enough range to allow it to go into runaway like the Moogerfooger MF-101 and others of it’s ilk as well. I will be looking at this to build a clone of my own. Thanks for taking the tome to do another great post.

    • joe


      Wow — cool idea for the dual-axis wah with foot-controllable Q. Has anyone ever done a two-axis control for an analog pedal? (The digital footpedal controller I use, the KMI SoftStep, supports an insane number of foot gestures, not that I’ve had the time to figure out how to use them much.)

      And yes — that’s similar to what I was thinking about the filter ranges — the option of going more extreme. 🙂

      • mwseniff

        There were a couple of Morley’s and a Zoom multi-FX that had dual axis controls. I also saw a very cool dual axis pedal a machinist made for his pedal steel, it had volume and tone. That controller was a real work of the machinist’s art with ball bearings and adjustments for throw, friction etc. Probably would cost a fortune to mass produce but it was very sweet to play. I love volume and wahs a lot and have worn out the action of many of them to the point where they sink down as soon as I take my foot off. They are very musically expressive for me.

        I will be looking at the schematics online with an eye to construction. It would be cool to apply midi control as well but that would require some designing.

      • el reclusa

        I have an ancient DeArmond 610 dual-axis volume & tone control pedal that can’t be newer than the late ’50s. Totally passive, and works surprisingly well.

      • jeremy

        the Fender fuzz wah pedal has a dual axis controller. this is how they describe the reissue…

        The Fender Fuzz Wah and Fender Volume/Tone feature clever dual action treadle plates that not only rock forwards and backwards like a traditional wah-wah, but also move from left to right.

        For example, when using the Fender Fuzz Wah, rocking back and forth manipulates the wah-wah filter envelope as you would expect, while moving the treadle to the right increases the amount of fuzz.

  • As I recall, Frederic Effects has done some stuff with the Syntech Harmonic Energizer… ah, here it is –

  • Digital Larry

    Here’s a page on the Korg MS-20 filter, which is a voltage controlled state variable filter, that has some clipping diodes in there.

    Pretty sure this approach can be adapted.

    • mwseniff

      MS-20’s are very cool synths a pal of mine has one. There is also a pretty convincing iOS app for the iPad which I have been playing with the last couple of weeks. The article Digital Larry provided a link to also talks about the Monotron using the same filter setup. I have all three of the Monotrons (std, dual and echo) having gotten them for Father’s Day and my birthday from my daughter (great kid!!!). I have been using the analog input on these tiny Monotrons to process other signals, in fact I use them to process each other Dual>Echo>Standard and it creates some wild sounds. The Monotribe also has the same filter along with a sequencer and some beats for a lot of sound making potential. Best of all my dog Yoko gives me the strangest looks when I get them all freaking out together. Check out the little Monotrons which are all around $49 they are worth it alone to process guitar tone. You can carry them in you pocket easily,they have a ribbon controller that can be set for notes or continuous, and the batteries seem to last a long time. The built in spkrs are just loud enough to annoy those that deserve being annoyed at family gatherings, great for the upcoming holidays.

    • joe

      The cool article Larry links to includes a link to the Tim Escobedo MS-20 schematic, which I’ve been DYING to play with. Tim’s notes mention that the distortion sound of his 9V-powered circuit is kind of crappy and ponders whether adding clipping diodes would help. But like, um, where exactly would they go in the circuit (he asked, revealing the full extent of his ignorance)?

      BTW, I have a couple of cool clipping diode tools I made: various pairs and trios of diodes distributed across the poles of rotary switches. I like using them while breadboarding to audition various options. Works great.

      • mwseniff

        “BTW, I have a couple of cool clipping diode tools I made: various pairs and trios of diodes distributed across the poles of rotary switches. I like using them while breadboarding to audition various options. Works great”

        I built a similar device when I was playing with clipping diodes in tube amps many years ago. It had several types of diodes as well as LEDs and also had the ability to stack the diodes or LEDs in series to get more output before clipping. One thing I found I liked was having asymmetrical stacks of LEDs of different colors and types as well as mix and match combos of different color LEDs. Putting two or more colors of LEDs made some interesting but subtle changes (LEDs of different color and type fire at different voltages). I also played with dual color LEDs that are a pair of LEDs in parallel but reversed polarities in the same device(the kind that can be either red or green depending on the polarity of voltage applied). I thought the dual color LEDs sounded kind of interesting when used by themselves as they caused an asymmetrical clipping which was nicely abrasive in tone. I also had the ability to add resistance in series with any diode combo by having a stereo pot wired so each section was in series with one of the diode pairs. Adding the resistance gave some clean before clipping which made the circuit respond nicely to rolling back the guitar volume pot.

  • Digital Larry

    I have seen two approaches for clipping inside op-amp based state variable filters.

    #1 Put the clipping diodes to ground, with a small value (1k) series resistor to the op-amp’s output. The signal that continues to the next stage is taken from the place where the resistor meets the diodes. This is e.g. how the Klon Centaur does its distortion.

    #2 Put the diodes in the feedback loop of a non-inverting op-amp stage (one where the input signal goes the the “+” pin). This is more like a tube screamer distortion characteristic.

  • hey joe…

    look here. one of my friends worked this up, a cross between a harmonic percolator and a harmonic energizer.

    calls it the harmonic fusion engine.

  • WOW! Someone in Vancouver just posted on Craigslist asking $1800 for one of these!! I could buy a whole lot of pedals for that kinda’ coin. Hell, I could have 9 or 10 clones BUILT FOR ME for that price!

  • I just built the madbean version of this. Sounds cool. Not as cool as the one Joe has in the video. Anyone have any suggestions on how to vibe it up a little more. Maybe just swapping the IC’s? I bet new IC’s would lower the noise floor but could also kill some vibe. I might try but was looking to see if anyone has already done some testing to point me in a good direction.

    • joe

      LOL — I was under the impression that the one I’m playing was exactly the same as the Madbean project, ’cause he was part of the original thread where the gang reverse-engineered my original Systech.

      In any case, I think this circuit COULD be really hipped up, especially in the distortion department. But I haven’t had a chance to experiment yet, so I don’t have any great recommendations.

      In related news, a friend just loaned me a Son of Kong pedal from Spontaneous Audio Devices, a company run by one of Zappa’s old guitar techs. Like the Triskelion, it’s a Systech spin off, but with what seem to be a bunch of interesting extra features. I’ll be checking it out in the next few days, and I’ll report back!

  • Joe does yours have 1 IC or is it multiple IC’s? The Madbean is a quad TL074. So changing the distortion wouldn’t be as easy as dropping in a chip just for that section. Either way I may try a few IC’s and see if they make a difference. I’m guessing the modern chips will need to be bypassed but would be quieter and possibly sound better.

    I’ll let you know if I come up with anything good.

  • Great demo! You came up with sounds I never knew this pedal could do. I built mine from a Madbean PCB over a year ago and been tweaking it since. (like adding in a an expression pedal for the frequency control)
    I’ll have to meddle with mine some more as I’m sure I can get the range of tones you have out of it.

    • joe

      Thanks! BTW, since I posted that, my pal Tom Menrath from Vintage King turned me on to the Son of Kong pedal, from Spontaneous Audio devices. It’s made by ex-Zappa tech Arthur Sloatman. (Zappa, of course, was the best-known user of the Harmonic Energizer.) It’s a pedal I’d dreamed of making for years, though I never would have done it as well. Basically, it’s a super-high-end, super-hi-fi version of the SHE that does all the same freaky stuff and then some. Meanwhile it includes a studio-quality preamp and pro connectivity, so you could totally use it as a subtle studio tone-shaper. (I believe some Nashville players are using it exactly that way.) Really impressive!

      • Yeah saw that post and have been looking at their page. From other reading I knew that Frank had boosts and EQ (plus lots of pickup switching options) in built in his guitars and the Son of Kong seems like a floor unit meld of those circuits.
        Once all the management has left work I’ll be able to view their demo video and see/hear what it does 😀

  • geeanthony

    Speaking of the Museum of Lost Effects, I can’t decide if my Digitech XP 300 Space Station is useful or useless. I might be able to decide if I watched a video of you putting it through its paces. I seem to recall reading somewhere that you had one, and maybe you still do.

  • Jack

    Hi Joe, nice demo. I checked out the Son of Kong, which is luvly but a tad spendy. On a likewise tip, have you tried the new moog minifooger boost? it has a similar vibe with a dist/boost and filter (controllable by expression pedal), although not as accentuated.

    Any thoughts?

    • joe

      Hiya, Jack!

      Wow — your timing is perfect — my review of the new Minifoogers just went live at Premier Guitar. I liked the boost a lot — but it’s way more tame than the Systech and its descendants, including the Son of Kong. I don’t own a Kong, but I got to play one, and I was deeply impressed. Not only does it do all the Systech tricks and more, but it’s an incredibly good-sounding, audiophile signal path. I can easily imagine using it 100% of the time as your recording channel, even if you’re not doing the freaky filter stuff. So it’s a bit of an apples-and-oranges thing. If you want the Systech sound on a budget and have some soldering skills, I recommend the clone project from Mad Bean. Hope that helps! 🙂

  • Jack

    I actually meant the drive, sorry for the confusion. I had seen your review but hadn’t connected the name.

    I like the idea of building the Karate Chop but I’d really like to have the expression pedal control of the sweep.

    Thanks for your help.

    BTW, do you have a guy that fixes pedals? I have an old phase 90 that’s dead and haven’t been able to find anyone reliable on the east coast since Analog Mike stopped doing repairs.

    • joe

      No, I don’t know a reliable pedal-fixer. Pedal repairs often aren’t cost-effective, because by the time someone’s cracked it open and put it up on the bench, you’ll pay more than the thing is worth. But obviously, it may be different with a vintage device.

      I’d post a note on the forums at and I bet there’s a capable geek who’d love the work for a modest fee and the fun of it.

  • Sorry for commenting on an old post–if you’re still wondering more specifically about the filter type, it’s basically a Tow-Thomas biquad with a few extra parts. The Oberheim SEM’s filter has clipping diodes in the bandpass feedback path, supposedly to force oscillation to be a sine-wave. But that’s a KHN biquad. The closest thing to that diode placement would be on IC1_A, tube scremaer-style. On an MS-20 it would be closer to put them on IC1_C instead. Both of these are feedback diodes like a tube screamer though. Maybe I’ll try making a filter with hard clipping instead–will probably sound terrible but who knows.

    Source on biquad filters: Microelectronic Circuits, Sedra/Smith

  • Bebah Palulah

    At some point in the distant past I was talking about an aliaser I came up with in DSP. Couldn’t find the thread, so apropos of nothing here’s the sound.

    It is an envelope controlled aliaser (possibly dual) with square wave tremolo. I think it makes a variety of pretty wild sounds.

  • […] of Frank, he used the legendary and ultra-rare Systech Harmonic Energizer, a filter/distortion from the ’70s which the Outsider is based on. Edgy and dark, with […]

  • Preston Thrall

    Pat Thrall used a first edition ‘S.H.E’ pedal on the first Automatic Man album and Pat Travers “Heat In The Street”. When he purchased it at Don Wehrs Music City in ’74, it was labeled “Overdrive A” (light blue label with black font), as they also had a pedal called “Overdrive” (slightly different light blue label with black font).
    By the time other guitarists in the Bay Area heard that ‘sound’ and went to purchase, Systech had changed the name to Harmonic Energizer (red label with black font)

    • joe

      Preston! Sorry it took me so long to reply to your message — my notifications were screwed up. Well, you would know, wouldn’t you? I had no idea. That’s super interesting, because I never hear Pat’s name come up in relation to the S.H.E. I so appreciate the info!

  • Can’t believe I came across this only just NOW- I love my SHE (paid a lot for it on eBay in 2008). I’m in the band The Flaming Lips…. We used that all over our record “Embryonic”…. Running a Fender Musicmaster bass through it, tho, was the highlight. Really cool to learn all this stuff. What a crazy pedal! I also have their phase shifter. Magical stuff…

    With love,
    Steven Drozd

  • […] The Harmonic Energizer has been described as the “secret weapon” of Frank Zappa. Read more about it here. […]

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