Here's the technical data for my amp but I'm not sure where the headphone plug fits into this;
Technical data (according to manufacturer):
Output power: 2 x 250W/8Ω, 2 x 450W/4Ω, 2 x 800W/2Ω
Total harmonic distortion: <0,02%
S/N ratio: >90dB (1W/8Ω)
Frequency response: 0,2Hz-500kHz (-3dB)
Input impedance: 10kΩ
Dimensions: 570 x 440 x 230mm (amp) + 2 x 460 x 320 x 160mm (power supplies)
Weight: 47kg (amp) + 2 x 32kg (power suppli