How to Build the CMoy Pocket Amplifier - Tangentsoft How to Build the CMoy Pocket Amplifier. Chu Moy designed a very popular headphone amplifier that’s easy to build, and it can be built small enough to fit in a pocket, power supply and all.Parts · Assembling The Amplifier · Article Revision History · Getting Started in Audio DIY Headphone Amp for the PR-101 - Akitika Headphone Amp for the PR-101. The Headphone Amp fits under the tone/volume PCB, leaving the option slots free for more new projects! It can be customized for modern (low impedance, typically 18-32 Ohms) or old school (600 Ohms) head phones. Headphone Amp Schematics. Assembly Manual. The Headphone Amp assembly manual. Assembling the kit.