So, while waiting for money for amp parts to materialize, and amp parts to arrive in the mail, for some indiscernible reason I wanted to find out more about what makes a vibrato circuit tick (ha-ha).
I started looking at and playing with the Wobbletron by Tim Escobedo and some of the vibrato circuits in the “Stompboxology” papers. The Wobbletron is fun, but supposedly also quite hard to make, so I wanted to put something similar together for myself while learning something new in the process.
Trying to convert the phase shift circuit to opamp I noticed how similar this was to the first stage of both the Phase 90 and the Micro Fazer. I ended up ripping off the first stage of the Phase 90.
As for the LFO I went through 7-8 different ones from various circuits (Tremulus Lune, Trembulator, Zombie Chorus, Ultra Flanger, Phase 90, Micro Fazer, Wobbletron etc.), but ended up with something very similar to the Zombie Chorus and Ultra Flanger that I liked the most.
I also tried different optocouplers in place of the FET, but they didn’t come close, so it’s the 2N5952 from the Phase 90 (which I had a bunch of). There’s a bonus in that since there’s only one stage you don’t have to match several of them. Other’s might work equally well, but I haven’t tried.
Finally, the depth pot. No idea where that came from. Seems to work well, but value subject to some experimentation.
I did breadboard this circuit and had zero noise issues, but haven’t tried the vero layout yet. I’m fairly confident it’ll be good, but you never know
Let me know what you think! Next, tap-tempo LFO would be cool…
Update (08.11.2013): Now verified as working, thanks to Michael. Also, now that I’ve got the tap-tempo micro controller working I’ve modified this circuit to go with it. Stay tuned