The Helios is a classic distortion pedal of the 80s, with some changes. The "Ruetz mod" (sweep control) is integrated, and a toggle switch for selecting the clipping diodes is also included.
The dimensions of the main pcb are 58mm x 47mm. It is also available as ready to solder kit:
This project is by Aion Electronics. Since the modifications featured in this project require some basic knowledge, this project is rather for more experienced builders.
Here is the direct link to the manual with layout and schematic:
Here you can find build reports on this project: Build Reports