Tremolo Effects Pedal

So for my friends birthday, I decided I’d get him something a little more personal than just a bar of chocolate say, or some money. So I set out to design and build him a Tremolo effects pedal for guitar!

First of course, I needed to figure out how a Tremolo pedal works, I’d heard one in action before, but never thought about what was going on in any depth. Tremolo is an effect created when you change the amplitude of the waveform, which basically changes the volume of the sound. The speed at which you modulate (change) the volume can be changed on the pedal, as can the amount it varies it.

With this in mind, I got to work on EagleCAD (a free schematic and PCB layout software package) designing my pedal. Of course I didn’t design it all from scratch, I patched different circuits together to create it:

This circuit essentially works like this: The bottom section, with the four capacitors, is a sine wave generator. Hooked up to an op-amp (LM324), so as to make sure current could be drawn from it (without the op-amp, if you attempted to use the sine wave signal for anything, it would collapse). There are two potentiometers here, R1 is the potentiometer controlling the amount of modulation the sine wave applies to the signal, R2 is controlling the frequency. The modulation is physically applied to the feedback loop of the top op-amp (another LM324) through the transistor, which then applies it to the signal.

The power, ground, input, output and switch terminals are so they can be connected to their appropriate off board components.

After designing this schematic, I created a PCB:

I am currently waiting for my PCB to be built (by OSHPark), but when I get them back and test them, I will write another post. If they work, I may even sell them as a kit!

Leave any feedback (pun intended) below.

Cheers, Tom