NuPrime STA 9 Power Amplifier - Silver Single End Class A + D amplifier design Bridgeable allowing switch between stereo or mono mode Power: 2 X 120W at 8 & 4 Ohms / 1 X 290W @ 8 ohm and 4 Ohms Peak Output Power: 2 X 280W / 1 X 320W @ 8 Ohms and 4 Ohms 600 KHz switching frequency for accurate reproduction of musical signal