Venkat, when I went to audition V663 in BB, the sales person said, Yamaha quotes the Peak power and not the continuous power (like Denon). Is that a pblm? how does the receivers actually operate on the different power ranges?
Not really as issue if you understand the terms.
As I have explained elsewhere, when you compare two amplifiers, you have to remove all external factors that could alter or affect the measurements. Generally two amplifiers are compared by sending a steady tone at a particular frequency (1Khz) and into identical speaker impedance (say 8 ohms) for a particular period of time. This is called continuous power.
When you are playing a movie or music, such ideal conditions do not happen. Frequencies vary from 20 to 20,000 Hz. An amplifier needs more power for lower frequencies. If the sound coming out has more lower frequency sound, the amplifier will be stretched to handle it at the same amplitude.
Peak power is needed to handle sudden spurts in sound such as an explosion, a gun shot, or a scream that needs more momentary power. Peak power is always more than continuous power but lasts for a very short time. What is needed for peak power is the capacity of the power unit inside the amplifier to deliver additional current instantaneously. This is misused by manufacturers to represent that their equipment has more power.
But this can be handled easily. Multiply the peak power specified by 0.707 to get continuous power. In other words continuous power is 70.7% of quoted peak power. So if a unit is quoted as delivering 100 watts peak power, it can deliver roughly 70 watts of continuous power.
Most reputed manufacturers will specify both figures as required by the laws of various countries. In addition, for multi channel amps, they have to specify how much power can all channels deliver when they are all driven at the same time. That means I am pushing 1Khz tone with a impedance of 8 ohms into all
the channels at the same
time. This is termed as 'all channels driven'.
All this is specified at acceptable distortion levels specified as THD. An amplifier may be able to deliver many times it rated power, but all you will hear is noise.
Many retailers may not understand these terms well and say anything to glorify or a kill a particular brand or a product. For actual details, look at the detailed brochure of the product as specified by the manufacturer.