The RAAL-requisite SR1a Earfield is not a standard headphone and will not work on most conventional headphone amplifiers. There are currently 2 different ways to connect and drive these headphones - a special ribbon amplifier (Schiit or Jotenheim R) or the interface box with a speaker amp. The SR1a interface box converts a typical speaker amplifier output into the load characteristic that the headphones require. Connect your speaker amplifier to the interface via speaker cables and plug the SR1a into the 4-pin XLR connection on the front of the interface box. NOTE:Interface RequirementS - 100W Speaker Amp needed (any loudspeaker amplifier will work).