The Chroma is a SP-1 Spectrum, a one band parametric EQ. The frequency knob sets the boosted frequency between 500Hz and 5 kHz, and the balance (or mix) knob adjusts the dry-to-wet signal ratio. The gain and Q (frequency width) are fixed. It only boosts frequencies, it does no cuts.
The dimensions of this pcb are 49,5mm x 49,5mm. 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