SPL HPm, Headphone monitoring amp with the Phonitor Matrix 500 module, Two separately adjustable headphone outputs, each with their own separate amplifier stages, Phase reversal of L and R channels, as well as stereo / mono / mute switching, Electronically balanced, Impedance: 10 kOhm, Max. input level: +21 dBu, Max. output level: +18 dBu @ 600 ohm, +15 dBu @ 300 ohm, +5 dBu @ 32 ohm, Frequency range: 10 - 10,000 Hz, Noise floor: -92.3 dBu (A-weighted), Total harmonic distortion (THD): 0.00024% (at an output level of 0 dBu and 600 ohm), 0 dBu = 0.775 V, Dual slot 500 series rack module, Weight: 0.8 kg