Probably Tetanus

Probably Tetanus
Probably Tetanus Vibrato Pedal

Good Ol’ Lockjaw

Whan that Aprill, with his shoures soote
The droghte of March hath perced to the roote
And bathed every veyne in swich licour,
Of which vertu engendred is the flour;

Geoffrey Chaucer, The Canterbury Tales

The only thing about Chaucer that stuck with me is the memory of hearing my 11th grade Brit Lit teacher recite the General Prologue in Middle English. Specifically “perced to the roote,” which is “pierced to the root,” but with all the extraneous syllables pronounced: pierce-ed to the root-uh. When he did it, it sounded like a cross between Merlin from the 1981 film Excalibur and The Swedish Chef.

When the shard of metal went into my foot, that’s what I thought of. Pierce-ed to the root-uh.

I had been trying to build another motionless chorus for weeks without success. To get my head out of it, I decided to put it down for a bit and build something simpler to get a quick win. Maybe a Tim Escobedo circuit. Then I thought that I’d try to update it to modern parts and maybe add a clean blend, which turned into a whole thing where it worked on the breadboard but not the vero, yadda yadda. I soldered in a bias resistor for what I hoped would be the last time and assertively hopped off of my bar stool to get my test guitar. When I put my foot down, I stepped on a resistor lead, which went straight into my foot with a popping feeling and/or sound.

I sat back down and contemplated. I scanned my bench for ideas. Tweezers? Nah. Needle nose pliers? Maybe. Ah, hemostats—those are vaguely medical. I had a sense of how long this wire would be, but as they say, everything is longer when you’re pulling it out of your foot meat. I stopped briefly, wondering if it was going to turn into the elevator from The Shining when I got it all the way out, but really, what better time to have a hot soldering iron ready to go? It didn’t come to that.

I emailed my doc the next day with the subject line, “Not Urgent; Puncture Wound.” No one could remember when I had my last tetanus shot, so I had to get one. If any pedals try to give me diphtheria or pertussis now, I’m also covered on that front, but I guess I have to give up soldering in socks.


In 2004, Tim Escobedo published the Wobbletron, which he called a vibrato, even though it has elements of a phase shifter and is described as “tremolo-like.” As far as I understand it, the differences are:

Vibrato: wiggling the pitch back and forth
Tremolo: wiggling the volume back and forth
Phaser: Cancelling out a small band of frequencies and wiggling the frequency back and forth

My guess, based on mostly feelings and intuition without any electrical engineering, is that it’s a one-stage phaser, which doesn’t make for a very pronounced phase effect (Typically Unfazed is a four-stage, for example). I think there’s one side of the first transistor that’s in phase with the input and one that’s not, and the LFO switching between emphasizing one or the other at the JFET. I can imagine that during the transition there would be a slight pitch shift, making this a vibrato, although the circuit may not be an idealized version of any of that. The whole point of Tim Escobedo’s Folk Urban project was to make this stuff accessible, not perfect, so it’s more gut bucket and washboard than Stradivarius, which is fine with me. I have seen Joshua Bell tear apart a Strad and have also seen Buckwheat Zydeco’s washboard player pull off a face-melting washboard solo, and to say that one was inherently better than the other would be asinine.

Regardless, the Probably Tetanus may sound nothing like the original Wobbletron. Some of the parts are obsolete, and part of my personal challenge was to make it work with the junk I had on hand, like 2N3904s and a 2N5457 instead of MPSA18s and a J201. I technically looked up the spec sheets for these and tried to compare them, but it’s like the part of every Star Trek episode where Geordi starts explaining that he’s setting up a phase-inverted tachyon field for total protonic reversal and it’s obviously just MacGuffin, MacGuffin, MacGuffin. I did a brute force attack on it by naively substituting resistors or sometimes hooking up a potentiometer, finding a spot that seemed right, and then reading the resistance with a meter. I eventually got it working.

The controls are Speed and Depth, which control the LFO. If the depth knob is turned down too far the effect goes away completely, so I also added a Blend knob that lets a variable amount of original signal through. Adding in some clean allows the effect to go further into the background than the depth knob could accomplish on its own, and can also minimize that thing where you hit a note at exactly the wrong part of the cycle and it has zero attack. The blender is dylan159’s Dry Blender, which also acts as a buffer. This pedal also got modded in mid-production to include a Bias control, which is the unlabeled knob on the side. Changing the bias of Q1 has an impact on the “phasiness” of the sound and can also add distortion at extreme settings.

Vital Stats

Weeble Wobble
Soothing Floral Design
Clostridium tetani
Life-Changing Washboard Solo


I find it interesting, especially with the clean blend and bias controls, which give a surprising amount of variation. At most settings, it registers more as tremolo to me, but perhaps an odd tremolo—not like a textbook Boss TR-2 or whatever.

The following example is the Coronacaster > Probably Tetanus > Fender Deluxe with some reverb. The first section is about as spacey as I can make it, the second section has the clean blend engaged to just add a little movement in the background, and the last section has the transistor wildly misbiased to show the range. The amp settings were unchanged between parts.

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