<font color='#000000'>I will be very surprised that Yamaha receivers use Class B since it is rarely in audio. Most likely it is Class AB.
And following is an excerpt from AudioAsylum which describes the technology is most concise and user friendly form:
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Quote </td></tr><tr><td id="QUOTE">Class A amplifiers often consist of a driven transistor
connected from output to positive power supply and a constant
current transistor connected from output to negative power
supply. The signal to the driven transistor modulates the
output voltage and the output current. With no input signal,
the constant bias current flows directly from the positive
supply to the negative supply, resulting in no output current,
yet lots of power consumed. More sophisticated Class A amps
have both transistors driven (in a push-pull fashion).
Class B amplifiers consist of a driven transistor connected
from output to positive power supply and another driven
transistor connected from output to negative power supply. The
signal drives one transistor on while the other is off, so in a
Class B amp, no power is wasted going from the positive supply
straight to the negative supply.
Class AB amplifiers are almost the same as Class B amplifiers
in that they have two driven transistors. However, Class AB
amplifiers differ from Class B amplifiers in that they have a
small idle current flowing from positive supply to negative
supply even when there is no input signal. This idle current
slightly increases power consumption, but does not increase it
anywhere near as much as Class A. This idle current also
corrects almost all of the nonlinearity associated with
crossover distortion. These amplifiers are called Class AB
rather than Class A because with large signals, they behave
like Class B amplifiers, but with small signals, they behave
like Class A amplifiers. Most amplifiers on the market are
Class AB.
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