Microamp ha400 behringer ha400 the behringer microamp ha400 is not only compact but can also power up to four pairs of headphones and up to four independent volumes p p this stereo headphone amplifier can be used with practically any headphones four of them at the same time if necessary p p four different people can listen to the main mix while recording and each listener can determine their own volume level using the dedicated output level controls p p when a recordi