This website is a resource for the design and building of headphone amplifiers. The HA-1 is a portable battery powered headphone amplifier with a built in Lithium Ion battery and charger. The amplifier is based on a National Semiconductor LM4881 headphone amplifier IC. This headphone amplifier is unique in that it uses a digital potentiometer as a volume control, most portable headphone amplifiers use a standard audio taper potentiometer.

This website contains schematics, bill of materials, PCB layout drawings, and chassis cutout templates. You can also purchase PCB boards and parts in the online store.