When I connect a turntable to my HD6, why is the volume extremely low?

Some turntables do not have a built-in preamps and as a result you will need to add an external phono preamp between your turntable and the HD6. Many turntables, however, (such as the Music Hall USB-1 or Audio Technica AT-LP120) have a built-in preamp and include a switch on the back for "line" or “phono”. For Audioengine powered speakers select "line".