The Sonifex RB-HD6 Headphone Amplifier is a 1U rack-mount which distributes stereo audio to up to 6 different sets of headphones, or can be used as 6 independent headphone amplifiers, each with their own input and volume control. A typical application might be to provide common headphone feeds for guests in a radio studio, with a separately derived feed, perhaps including talk-back, for the presenter.
 
The main stereo input is on XLR-3 connectors on the rear panel which are electronically balanced and can be wired unbalanced. A stereo/mono input select switch on the rear panel sums left and right outputs to provide a mono feed to the headphones. The unit can receive an override audio signal via a jack socket for each output channel. Plugging in the jack plug will divert the headphone output from the master audio signal to the audio present on the jack plug. The override audio inputs can also be individually configured as parallel outputs of the front sockets, by setting internal jumpers. The master volume control adjusts overall level of the 6 outputs and does not affect the level of channels using the override inputs. The master volume can be disabled by internal jumpers.