User Manual

4
EEEngine
EEEngine combines the sound quality of Class AB
circuitry while maintaining the efficiency of Class D
circuitry. Combining positive aspects of both Class AB
and Class D may seem simple by concept, but it took
years of extensive engineering efforts to achieve this
technology on a mass production base.
EEEngine overcomes problems conventional amplifier
topologies while providing advantages in all areas,
offering a dramatic leap in power amplifier design. It
realizes efficiency that matches Class D without
compromising the sound quality of a Class AB amplifier.
The patented EEEngine technology is scalable and can
be found on a wide range of Yamaha power amplifiers
from the value class P series to the flagship TXn series.
EEEngine tracks the audio signal to always provide the
minimum power needed for the final output stage,
allowing for surprising improvement in efficiency. It
utilizes Class D operation to provide the power at the
final output stage of Class AB operation. Almost all of
the current energy is output as the audio signal, and just
a small fraction of the remaining energy is emitted as
heat dissipation through the heatsink.
With the final output stage operating as Class AB, the
output signal is of remarkably high sound quality. There
is none of the deterioration of frequency response and
damping factor or unwanted EMC, as conversion of the
audio signal to a PWM signal does not take place. Plus,
EEEngine is designed to operate perfectly while keeping
the power amplifier heat generation to a minimum,
regardless of the load requirements. All together
EEEngine offers Class AB sound quality with efficiency
that matches Class D. EEEngine circuitry was uprated
for TXn and Tn series amplifiers with a new high
efficiency electrical current buffer FET driver circuit to
withstand the power and 2 ohm loads that the amplifiers
will drive.
[ Fig.7 ] EEEngine operational waveform
EEEngine vs competitor technology
There is one well respected amplifier manufacturer with
a proprietary amplifier topology which shares the same
concept of combining Class AB amplification and Class
D power supply operation. Both technologies track the
audio signal to always provide the minimum power
required for the final output stage. Two technologies are
different however, in its tracking operation methods.
Signals of higher frequencies require a higher slew rate*,
and are harder to track. Slew rate is a measure of the
ability of an amplifier to respond to very fast changes in
signal voltage. To compensate for the inability to keep
up with changes in signal voltage, this competitor
technology adds a delay to the input signal. This delay
gives the Class D power supply more time to respond to
sharp changes in voltage, but it must be noted that
manipulating the audio signal will inevitably have effect
on the final sonic quality.
Yamaha’s EEEngine takes a different approach to
compensate for Class D power supply’s limitation in
keeping up with sharp changes in voltage by adding an
auxiliary “high speed buffer” power supply. This high
speed power supply circuit is activated only when Class
D power supply alone is not able to keep up with the
speed. This “high speed buffer” mechanism allows
EEEngine to respond to quick voltage changes without
manipulating the audio signal and degrading sound
quality. The elimination of unwanted and excessive
components to the audio line is a reflection of Yamaha’s
philosophy of delivering natural output signal that is
faithful to the input signal.
* Slew rate affects the ability of an amplifier to accurately
render complex waveforms at high power levels. A higher