Max input level: +19dBu.
There is no recommended input level. The input level that works for a particular installation depends on gain staging throughout the signal chain which should be optimised to avoid noise and clipping. A good starting point for the level control is the 0 dB setting in the middle. If the loudspeaker is too sensitive then turn the knob in the -dB direction, however be very careful not to introduce clipping in the preceding equipment when trying to achieve the desired listening level. If the loudspeaker is not sensitive enough then turn the knob in the +dB direction, however be very careful not to be amplifying source noise.