My tremolos are easily my favourite circuits, and have occupied more of my design time than anything else. This was my first effect design from scratch, which I started in high school. Development took over a decade before I was happy with it.
By shining a fading light against a photo-sensitive device, this tremolo uses all analog photo-coupling to restrict and fluctuate the output volume.
Symmetry switch: This toggles between two modes which are subtly different. The asymmetric mode (up) has a slightly uneven rhythmic pattern. I feel this mode is sweeter, as it has a less obvious tempo. The square wave in this mode stays longer in the 'on' state, giving less gap time, which I also prefer.
The symmetrical mode (down) has an even 360 degree spin, with a deeper scooping bottom. It has a classically pronounced tremolo shape. Think spaghetti westerns.
This circuit operates with in a split rail power supply for increased headroom, while maintaining a very low noise level.
As with all of my tremolo models, you should expected perceived unity volume with all depth and rate settings, without having to make any manual volume adjustments. The wetlevel can be adjusted internally by a trimpot.