After a long, long, long road, I have finally settled on version 2 of the Blue Warbler. Version 1 never got a full build thread on here, but I'm making up for it now!
This has been a very frustrating process, but I'm really happy with the new circuit.
Schematic
What it sounds like ... Well, mostly.
I changed the depth control after shooting this video (this is the one I made for Scooter). It's almost identical, but I improved the depth further to have a better feel to dial in subtler settings.
How It Works/Build Document
I have written an EXTENSIVE "How It Works" in the build document, which also contains a perfboard layout. [size=150pt]https://docs.google.com/document/d/1aM2U7PL7NiMd_RaaV-7s5epvqRBPM0ZSbdbKHx96tRw/edit#[/size]
Here is a brief rundown: The audio path is based on the Tim Escobedo Wobbletron and Bearfoot Magnavibe, with a couple changes to get what I felt was a better overall circuit. It's a simple two-stage phaser that mixes some of the output from the source with the oscillating output from the drain. The tremolo mode simply disconnects the steady source output.
The build doc contains a list of LDRs that work right in this circuit, with notes. My favorite was the Silonex 7530/7532 (they're the same thing), which Smallbear carries. To be thorough, I also tested a bunch of photocouplers, but they had worse performance (and they're more expensive).
The LFO is a variation of the basic phase shift oscillator in the EA Tremolo with some modifications. The depth control is the biggest reason this took so long, as I've been searching for over a year to find a phase shift oscillator implementation that can drive multiple LEDs and turn them on at minimum depth. In the build doc I detail some ways to adjust the speed range of the LFO.
The Envelope control is a simple one based on what I used for the Bearhug Compressor. The new Sense control is pretty cool -- it controls the threshold, decay, and a low pass filter all at the same time, which helps dial in different pickups.
As far as what's different in the new version from Version 1:
1) Even cheaper to build. The most expensive parts now are a $1 photocoupler and a 25c BS170, both of which have less expensive substitutes. 2) Better depth control. The old one (and the one in the Magnavibe) loses bass as you turn down the depth, and was mostly useless for tremolo mode. The new one works just like you expect a normal depth control to work and does not change the tone. It also doesn't interact with the speed as much. 3) Better tremolo mode with a simpler implementation -- and no more volume drop! The volume between the two modes is pretty much identical. 4) Better input impedance. 5) Smaller less complicated circuit overall. The perfboard layout even fits in a 1590A if you're careful.
Jacob's (JMK's) PCB project will be very close to this, but there may be one or two adjustments to his preference.
Here's an etch mask. I just did it from the perfboard layout, since I wasn't really happy with anything I was doing in Eagle. Parts layout is the same.
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