Unlike most music equipment, the HA-1A is not designed to make you sound good. Instead, it is designed to tell you the truth about how you sound. If your fingers make squeaky noises on the strings when you move, if your E string is twice as loud as your D, if your intonation is lousy – the HA-1A will tell you. And if you sound great, it’ll tell you that, too. There are no tone controls, effects loop, enhance knobs, or subharmonic thingamajigs: the HA-1A tells you what you do sound like, not what you wish you sounded like (HA-IA Headphone Practice Amplifier Owners Manual). Works great. Best headphone amp I’ve ever had for bass guitar. I hear it easily when band is doing sound checks and I want to prep and warm up. Personally, I’ve had iRigs and Bigheads and Preamps/Amps with Headphone Out/Aux In and like the HA-1A the best. Love the powerful separate volumes for my bass and iPhone/iPAD, and the choice to power with two 9 volt batteries or walwart (included). FYI this is a cross listing from the Amps, Preamps, and Cabinets section. Shipping Contiguous United States included. No trades please. PDFs of the Owners Manual and Schematic are attached below this picture for further details about this awesome piece of gear. Thank you.