Good Ol’ Lockjaw
Whan that Aprill, with his shoures soote
Geoffrey Chaucer, The Canterbury Tales
The droghte of March hath perced to the roote
And bathed every veyne in swich licour,
Of which vertu engendred is the flour;
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 snipped-off 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.
Details
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 up and down
Phaser: Cancelling out a small band of frequencies and wiggling that band 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. It’s more gut bucket and washboard than Stradivarius. I’ve seen Joshua Bell tear apart a Strad, but have also seen Buckwheat Zydeco’s washboard player pull off a face-melting washboard solo, and they’re both great in their own way.
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.
Update: 6/27/2024
I made this incorrectly. I have no idea what made me think of this now, approximately 13 months after I originally built it, but I had the middle lug of the blend pot going to ground instead of the reference voltage. That made things “pretty weird” (in the engineering sense of the term) and I think a lot of the stuff I did with the bias knob may have been to hide the annoying ringing sound with distortion and generally poor sound quality. Sending the center to Vref made this sound like a different pedal, to the point where I realized that the bias control was probably more of a hindrance than a help. I set it to where it sounded best to me, snipped the wires, and measured it, and it came in at 679k—shockingly close to the 680k fixed resistor that I had in there initially, so I put that back in too. I’ve updated the schematic to reflect this change.
Vital Stats
Sound
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 from after the update, when I fixed the blend knob functionality. It is in three sections, all into a Fender Deluxe-ish amp set clean with some reverb:
- Coronacaster > Probably Tetanus; slow speed on the vibrato and single notes
- Emomaster > Probably Tetanus; faster speed on the vibrato and farmer chords
- Coronacaster > Anhedona > Probably Tetanus > even more reverb; mid speed but tons of fuzz and reverb and reverb into fuzz
