Thank you for viewing. I am selling this item to adjust to changes in my living environment. This is a practice headphone amplifier from the legendary Jirau (Mr. Ikujiro Fukuda) workshop. Despite its size, it boasts high output and high sound quality. It can be used in a variety of ways, from quick practice sessions on the go with batteries to building a daily reference environment when connected to an adapter. *Although Jirau does not recommend it, it is said to have enough output to easily drive passive speakers. Please try this at your own risk. I mostly used it at home, so it doesn't show much wear and tear. However, as it is a product from over 15 years ago, it has some signs of aging. There are no functional issues, and I believe it can still be used on the front lines. Bassists who want to seriously review their touch and sound should definitely consider this. Power source: 9V battery or AC adapter. The HPM is a headphone amplifier with master and audio volume adjustment functions. - Model name: HPM - Input terminals: LINE INPUT, BRASS INPUT - Output terminals: PHONES 1, PHONES 2 - Volume adjustment: MASTER VOLUME, AUDIO VOLUME Comes with the original box and instruction manual. A ZOOM AC adapter is included as a bonus.