Yamaha MX-A5200 11CH Amplifier Preliminary Measurements\n\nFound a perplexing issue on the MX-A5200 11CH amplifier. The FFT in bridged mode produces much higher odd order harmonic distortion products. I attached a plot comparing the single amp vs bridged amp modes both tested at 1 watt. This is a shame because the bridged mode produced really impressive power levels as you can see it the plots below the FFT.\n\n\nCH1 (blue) single amp mode\nCH 2 (red) bridged mode\nNote: the odd harmonics are >10dB worse for bridged vs single mode. When the amp is cold, the differences aren't as dramatic as when you let the amp run steadystate for a long period of time. Also, the 120Hz hum (power supply hum after rectifier circuit) gives me pause.\n\nYet, bridged mode belted out some impressive power #s far exceeding the 200watt (8 ohm) rating by Yamaha.\n\n\n\n250 watts\/ch 0.1% THD+N both channels driven, 8 ohms!\n\n\n\n400 watts\/ch 0.1% THD+N, 2CH driven, 4 ohms!\n\nI wish things would be a bit more tidy with the FFT so I could be happy about writing up this review :\/\nIn general, do most amps have increased distortion when bridged?\n\nBut in this case, the bridged-mode distortion is just higher than usual?\n\nIs Yamaha saying that it's expected or acceptable with the bridged-mode?\n\nBut when not bridged, the distortion looks good?