http://stereophile.com/solidpoweramps/804mcintosh/index5.html
The McIntosh's maximum output power depended on the output tap chosen and the load, but when the tap was matched to the load, the amplifier easily exceeded its specified 500W at our 1% THD definition of clipping. The 8 ohm tap delivered no less than 720W into 8 ohms (28.6dBW), for example (fig.4), with similar deliveries into 4 and 2 ohms from their respective taps (figs.5 and 6). Despite the slight increase in source impedance, the MC501's ability to deliver current into the speaker load did increase with the decreasing output transformer tap. The 8 ohm tap was limited to 225W into 2 ohms (17.5dBW), for example, while the 4 ohm tap delivered 1000W (24dBW), the 2 ohm tap 630W (22dBW).
The McIntosh's maximum output power depended on the output tap chosen and the load, but when the tap was matched to the load, the amplifier easily exceeded its specified 500W at our 1% THD definition of clipping. The 8 ohm tap delivered no less than 720W into 8 ohms (28.6dBW), for example (fig.4), with similar deliveries into 4 and 2 ohms from their respective taps (figs.5 and 6). Despite the slight increase in source impedance, the MC501's ability to deliver current into the speaker load did increase with the decreasing output transformer tap. The 8 ohm tap was limited to 225W into 2 ohms (17.5dBW), for example, while the 4 ohm tap delivered 1000W (24dBW), the 2 ohm tap 630W (22dBW).