The HPAJr Headphone Amplifier is a compact, battery / external dc powered unit designed to interface your favorite full-sized professional headphone to a variety of audio input sources. Now you won't be limited to small, poor quality "in-ear" or "walkman" type headphones for your monitoring or listening needs. The HPAJr will allow you to drive headphones of many impedances to more than adequate listening levels with a full, rich sound not obtainable at low output levels or with lightweight "personal" earpiece / headphones. You can use the HPAJr for such professional purposes as increasing monitor levels from: mixers, portable VCR's, tape recorders or R-DAT's; personal listening to keyboards and synthesizers or monitoring of home studio gear. Compact and durable, the HPAJr comes with a sturdy belt clip for complete portability.