Helios

Aion FX from Des Moines, IA has helped guitarists build studio-quality effects since 2011. They document circuit evolution, showing how classic designs built upon earlier foundations.

The Helios recreates the ProCo RAT Distortion (1978), an evolution of the MXR Distortion+ with the same basic op-amp gain stage and diode-to-ground clipping, but with altered EQ, a sophisticated tone control, and an output buffer. The Aion version adds clipping switches and a Sweep control for enhanced versatility.

Kurt Cobain's "Smells Like Teen Spirit" tone made the RAT a grunge icon, but it's been used across genres from metal to country. The circuit's aggressive character and effective tone control made it more versatile than its Distortion+ ancestor. The Aion PCB explores variations while maintaining the core RAT topology.