This is a story before the pictures.
A few weeks ago, I had counted up my all my pedal builds and realized that I would very soon hit #50. I knew I wanted to do something special, and the Turkey Day competition gave me added incentive to go beyond just soldering up a complicated project -- I considered doing a Deluxe Memory Man, which is my ultimate goal for the year -- and create something at least
somewhat new.
The first pedal I ever tried to build was a Tremulus Lune. I'm not sure exactly why ... I knew almost nothing, though I did at least have a lead on finding parts (Smallbear!), and simply looked up a layout online. It was veroboard, and I'd never seen the stuff, so I tried faking it on perfboard. It didn't work of course (the remnants are still in my box of fail), and I also had no idea how to troubleshoot and my only tool to do so was an analog multimeter. That was in January ... I think I've learned quite a bit since then, mostly by building or breadboarding almost everything I could find and reading everything I could find about the effects as I made them. I still have a ways to go ... I haven't touched bucket brigade technology, and there are bits of filtering that are something of a mystery to me. Anyway, tremolos are still one of my favorite circuits to build. And since this was a milestone of sorts for me, I knew I wanted something with an LFO. So I started breadboarding some things, like a fuzz trem and some other weird stuff. But just making another tremolo didn't seem like anything special, especially after I realized it would be a contest entry.
Then I remembered RG Keen's "Vibromatic," which is an envelope circuit that kills the LFO of an EA Tremolo. That seemed promising. Then the next day, one of the forum members, HaveYouSeenHim, brought up the Magnavibe and sent a vero layout. I'd worked with another design descended from the Warbletron recently, Madbean's Quadrovibe, and remembered that it was easily converted to a tremolo design. I liked the sound of the Magnavibe on its own (it's a little milder than a univibe sound, really the kind of vibe I like), but there were some issues with the tremolo mode that I wanted to improve. So I decided to pair something similar to the Magnavibe with the Vibramatic.
These were my goals with what I created:
1) Since the circuit was descended from familiar DIY circuitry, I wanted it to be accessible to other DIYers. So no unobtanium parts. So no weird resistor or cap values -- just the stuff that most people will have in their bin.
2) No parts matching, biasing issues, etc. For the most part I succeeded in this one.
3) The circuit had to be as simple as possible while still sounding good.
4) Whatever I created had to be easily used in a live situation. So anything with 10 knobs and switches was out.
Here's what I ended up with:
PDF here:
https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Nonmini%20builds/Blue%20warbler%20vibe%20schematic%201.2.pdfHere's what it sounds like:
[EDIT 10/14/12: Published the annotations to the video.]
What's going on hereThe audio pathThis is very, very close to the Magnavibe's dry path, with the following changes: The gain has been increased to accommodate the signal split into the envelope circuitry, and the output caps have been changed to provide a slightly different voicing. The end result is pretty similar to the original, but there's more high end content remaining in Vibe mode and the warble is just a little different. The tremolo switch moves one of the LDR's legs from the buffered output to a series resistance between the two caps. This prevents any volume change between modes (except in the furthest CCW depth settings) and also prevents a really loud POP when switching over, which is an improvement over simply grounding the LDR, which is how I've seen it done in some other circuits related to the Wobbletron.
The volume trimmer will be set near max but was included to accommodate transistor gain variances.
The LFOThe LFO is, again, lifted from the Magnavibe, but that's just basically the LFO from the EA Tremolo with a different variable resistance element. I chose a BC547B/C because it softened the wave. It still gets plenty of wobble but sounds more natural on the tremolo setting. I added a series LED, swapped out the needlessly complicated "12K" depth and rate pots (25K with a parallel resistor) for more common values (increasing the rate pot value to ensure access to some slower settings). The LFO section is also electronically isolated from the audio path.
The EnvelopeAlthough I started with RG's envelope, I went through a few more types of envelope circuits (the Nurse Quacky's, the Meatball's, and I even tried a couple compressor envelope/rectifier circuits, but they didn't work at all) and ended up with one that uses bits of some of them but looks and behaves a little differently from all of them. Specifically, this envelope circuit solved a few issues that others had in this specific circuit, like OP amp distortion/transistor sound from the input signal and some finickyness with the envelope actually triggering and altering the LFO. Some just killed the LFO in all settings. I also note that this one is mostly backwards ... the references voltages are in weird places. The transistor is a FET and is turned around backwards. 2N3904, the transistor in RG's envelope and the Nurse Quacky, didn't work; 2N5457 had the only completely reliable results, with all 30 I had on hand working as desired. And the LEDs are asymmetrical rather than matched like in some circuits (e.g. Nurse Quacky). I guess what I'm trying to say is, this is probably the only piece of circuitry I've ever used that might actually be unique, but who knows if it can be used in anything else. In any case, I'm very grateful to the people mentioned above for sharing their ideas and providing a starting framework.
The decay control should be set between ~10K and 50k. Lower settings may provide distortion. I believe it's actually the LEDs
clipping, which is weird. My stock setting is 33K, which seems to provide the best balance and variety at any given sense setting, though hotter pickups may require a lower value. The 22nF cap was a good size to avoid too much rippling. (Credit goes to Mark Hammer for making this suggestion for the Nurse Quacky, and to Runoff Groove for noting this in their build doc.)
Note that there is no minimum setting on the Sensitivity control. This was done because some cool things can happen at both extremes, like the CW extreme killing the LFO except when playing, and the CCW extreme killing both the envelope and LFO. See the video for examples.
So after that novel, here's my official contest entry, the Blue Warbler Envelope Vibrato.
IT'S NOT A 1590A! SOUND THE ALARM! CALL THE GUARDS! FIND A PSYCHIATRIST! No, actually, remember rule #1 above? Most DIYers don't want anything to do with 1590As, so I decided to make it a comfortable fit for a 1590B. Here's the layout.
PDF:
https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Nonmini%20builds/Blue%20warbler%20vibe%201.2.pdfBut, come on ... you know I had to. Here's the 1590A layout. (The only changes are no electronics isolation between the envelope, audio, and LFO circuits, but I didn't get any ticking even on the breadboard with no filtering at all.)
PDF:
https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Blue%20warbler%20mini%20layout%201.2.pdfI was going to build this for my second entry fee (not as an extra entry, just for fun), but I got impatient. Rest assured, it will be soldered and boxed in the not too distant future.
Additional inspiration provided by: John Lyons (for his matching circuit boards). Additional thanks to Joshua McClarren (Gtr2/1776 Effects), who provided some insight and comments into curing the op-amp distortion issues. Hopefully I've provided adequate credit here, above, and in the schematic, but if anyone thinks I left out their contribution, please tell me.
And for good measure: total cost to build this was under $25.
DIYLC files are available upon request.
