LABS1 - Alternating Tremolos

This is the basic idea... Create a square wave and an inverted version of itself (one is high while the other is low and vice versa). Each square wave then controls a tremolo, with one tremolo modulating the clean signal and the other modulating a delay signal (although you could replace the delay with any effect really).

This gives the effect of rapidly crossfading between the dry and wet signals.

This schematic shows how I hooked it up:

Okay these low res images are terrible - try this schematic - I offically need a better web host...

Capacitors C2, 4, 7 & 8 are to prevent any "whooshing" by blocking the DC. In hindsight this would probably work as well with just one cap per tremolo, in series with the LDRs & depth pots.

Try to keep the grounds for the LED & oscillator seperate from the audio signal grounds, to keep ticking to a minimum.

In the video I used a microcontroller for the initial square wave, followed by a transistor buffer and an inverting transistor buffer to get the two waveforms.

An easy way would be to use a CD40106 oscillator, as you could then use a spare gate on the 40106 to invert the square wave. A bonus with the microcontroller is that I'd programmed in variable pulse width, allowing me to change the ratio of high to low in each square wave duty cycle. There are schems online for op amp oscillators that let you do this.

The gated tremolo effect is achieved by replacing the LED-->LDR combo with a TLP222 photo fet, and for the vibe sounds I just lobbed the square wave at pin 6 of the PT2399 via a 220k resistor.