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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
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