GOL tremelo project

Posted on Feb 7, 2014

This is a really good project for anyone wanting a good old fashioned tremelo pedal using the original optical coupling technology employed in such things as the Reslytone RT-18. I reckon it`s pretty unique with what`s around. There are any number of tremelo circuits on the net, but a lot them either don`t work at all or not that well. I tried nu

GOL tremelo project
Click here to download the full size of the above Circuit.

merous circuits and then tried to effect a simplified version of the Reslytone RT-18. Although I got it working, I found that it relies on a number of combinations of resistors and capacitors switched in banks to give the very smooth waveform it generates from the astable vibrator circuit. I cannot decipher the part of the schematic that does this. It`s just too ambiguous. After spending quite some time, I have a winner! The new circuit just completed works perfectly, runs on standard 9V DC, and produces no undesirable pumping because it uses an LED coupled to an LDR (light dependent resistor) to act as the variable volume control, just like the Reslytone RT-18. The repeat rate goes from 1. 5 times a second to about 15 times a second, and has a fully variable intensity from zero to almost a full cut-off. The oscillator is an op-amp Wein Bridge oscillator driving the LED / LDR via a Darlington transistor configuration. The signal from the guitar only passes through a simple transistor / FET coupling circuit. The op-amp just supplies pulsing to the LED, and also supplies the indicator LED on the top of the unit showing both the frequency & intensity of the tremelo. It`s a great little project for the tech inclined player, and cheap to make. It employs a true bypass stomp switch of course. I have designed the vero board layout which can be viewed here. I realise that there are any number of affordable whiz bang tremelos on the...

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