I am building a guitar effects pedal from a schematic I found online. Unfortunately the schematic is poor quality and hand-drawn, but there is a diagram of it constructed on veroboard (this is generally the way it is done in the world of effects pedal building.
It uses a PT2399 delay chip. From the creator's original post:
The chip's input stage is set up as a comparator with the aid of the Vref pin, so that gives us an ultra-amplified, squared-off waveform straight away.
The comparator means the input is quite heavily gated, so I only get sound out of it if I play my guitar very hard, or amplifying the signal before it gets to the pedal with an external device. Basically, it's not very responsive or sensitive.
I would like to make it so the required input volume is lower, and I can play the guitar more gently and still be able to trigger the comparator. The schematic:
And the veroboard diagram:
So the vref pin is pin 2 I believe (pinout here) and it is connected to pin 16 (the input) via R2. The audio input goes into pin 16 via a 47nF capacitor (C4) but I'm not too familiar with comparators, so I don't know which values to change. I've experimented but I don't think I'm on the right lines and I'm not getting any change in sensitivity. Can anyone help?