Cheap Delay
PT2399 based delay/echo module for modular synthesizer
This module is a digital echo/delay effect built around the PT2399 IC, commonly used in audio effects like guitar pedals. It’s inexpensive to build and has a distinctive lo-fi, gritty character, thanks to design limitations that prioritize simplicity and low cost over absolute audio fidelity.
The original schematic comes from Look Mum No Computer. I tweaked a few capacitor and resistor values here and there to better suit my needs.
Check out the project here: PT2399 Triple Splashback
The original schematic comes from Look Mum No Computer. I tweaked a few capacitor and resistor values here and there to better suit my needs.
Check out the project here: PT2399 Triple Splashback
Component List:
1x PT23991x LM7805 voltage regulator
1x TL072
3x 100kΩ resistor
1x 30kΩ resistor
4x 15kΩ resistor
4x 10kΩ resistor
2x 1kΩ resistor
5x 10µF capacitor
1x 0.33µF capacitor
7x 100nF capacitor
2x 4.7µF capacitor
2x 330pF capacitor
1x 680pF capacitor
2x Jack socket
2x 100kΩ potentiometer
There’s one knob for controlling the delay time, and another that adjusts both feedback and mix.
When the second potentiometer is turned all the way down, the delay becomes inaudible. This might not be ideal in some situations, but for my use on stage, it works perfectly fine.
You can tweak the delay time potentiometer to adjust its minimum and maximum range.
I’m using a 100k potentiometer because I really like the gritty sound the delay produces when the time is too long for the chip to handle.
Changing the C11 & C10 capacitors to larger values can also slightly tame the high frequencies.
I built my first echo with 680pF capacitors and now use 330pF for a noisier, more aggressive echo. Give it a try!
I think changing C15 might also impact the sound quality.
Look Mum No Computer used 2.2µF, while I switched to 680pF.
When the second potentiometer is turned all the way down, the delay becomes inaudible. This might not be ideal in some situations, but for my use on stage, it works perfectly fine.
You can tweak the delay time potentiometer to adjust its minimum and maximum range.
I’m using a 100k potentiometer because I really like the gritty sound the delay produces when the time is too long for the chip to handle.
Changing the C11 & C10 capacitors to larger values can also slightly tame the high frequencies.
I built my first echo with 680pF capacitors and now use 330pF for a noisier, more aggressive echo. Give it a try!
I think changing C15 might also impact the sound quality.
Look Mum No Computer used 2.2µF, while I switched to 680pF.
