Adcom GFA-555MS Operating Instructions Manual page 19

Power Rating (To FTC Requirements)
125 watts continuous average power into 8 ohms at any frequency between 20Hz and
20kHz with both channels driven at less than 0.04% THD.
200 watts continuous average power into 4 ohms at any frequency between 20Hz and
20kHz with both channels driven at less than 0.05% THD.—
400 watts continuous average power into 8 ohms at any frequency between 20Hz and
20kHz at less than 0.09% THD, bridged.—
IM Distortion (SMPTE)
1 watt to 125 watts into 8 ohms
1 watt to 200 watts into 4 ohms
IM Distortion (CCIF, Any Combination from 4kHz to 20kHz)
125 watts into 8 ohms
200 watts into 4 ohms
THD + Noise at 125 Watts into 8 Ohms
20Hz
1kHz
10kHz
20kHz
THD + Noise at 200 Watts into 4 Ohms
20Hz
1kHz
10kHz
20kHz
IM Distortion, Bridged (SMPTE)
1 watt to 400 watts into 8 ohms
GFA-555ms SPECIFICATIONS
≦0.009%
≦0.009%
≦0.002%
≦0.003%
0.004%
0.003%
0.006%
0.020%
0.005%
0.004%
0.020%
0.030%
≦0.05%