The design is pretty simple and easy to build. The main delay effects IC is PT2399 which is a cheap solution compared to using complicated and more expensive BBD IC such as MN3207 and the like. PT2399 is digital echo processing IC capable of producing up to 342mS delay with 1.0% THD. You can further expand this to more than 1 second but with the price of higher harmonic distortion which gives not pleasant sound. The resolution of the ADC of the IC is not disclosed on its datasheet, but it sounded good so I guess it’s around 16bit maybe.
Schematic
The circuit is composed of 4 simple blocks, the voltage regulator, input amplifier, delay processor, and output buffer. The input amplifier has a gain of 2 for better signal to noise ratio but small enough to avoid introducing distortion or clipping of signals.
Figure 1 – Schematic
The voltage regulator is a popular linear 7805 regulator which will provide 5 volts power to the PT2399 delay IC.
Frequency Response
The filter is designed so that it will attenuate frequencies lower that 100Hz. This will help reduce popping noise when switching the footswitch. It also attenuates the signal above 10kHz which is above guitars signal spectrum. This will help reduce hiss noise.
PCB Design
The PCB is a small 5cm x 5cm 2 layer PCB designed using Eagle PCB software. Below is the completed board assembly.