A few people have asked me about a single speed pot version of the
"Bipolar Disorder", so here it is, the "Vibracaster".
The tube section is basically the Valvecaster schematic. I prefer a 100K 'Gain' pot - but maybe a tremolo doesn't need overdrive too? So, the gain pot can be ditched and replaced with a 100K resistor.
With the 'Depth' pot turned down it's just a standard Valvecaster.
If you want it even 'cleaner' you can replace the 220k resistor at 12AU7 pin 1 with 100k, and the 100k resistor at 12AU7 pin 6 with 47k.
The LFO section is a phase shift oscillator - many thanks to R.G. for helping me to understand how they work.
This is on my breadboard and working right now, I'm using a 6111 submini tube on the breadboard, but it will work identically with a 12AU7.
I wanted to breadboard a phase shift oscillator for another project I'm working on. Then it occured to me that it would be perfect for a "Vibracaster" too. I wasn't going to actually make it into a pedal, but I guess I will - I like it a lot! I'm going to build it with a submini 6111 in a tiny enclosure, I won't bother with the gain control.
Oooooh! I hope someone esle builds it too!
EDIT: Oh, and I hooked up a 'Rate' LED (via a 4K7 resistor) from the emitter of the second transistor (the one on the right). The LED kathode goes directly to earth, obvioulsly.
