EEEngine Technology

Introduction

Yamaha's EEEngine (Energy Efficient Engine) technology makes power amplifiers more energy efficient than ever possible before. Along with energy efficiency, their light weight and compact size make them the perfect choice for S/R systems where a wide variety of instruments used in various facilities and large-scale systems can result in very high power consumption.

When conventional power amplifiers drive loads, they make use of only 20-30% of the electrical power they consume. In contrast, Yamaha's EEEngine technology is approximately twice as efficient. In other words, an EEEngine driven amplifier can obtain the same output as a conventional amplifier with only half the power consumption.

High Power No Longer Means High Heat Dissipation

In a conventional amplifier, a class-B SEPP (Single Ended Push-Pull) circuit is generally employed, but the output transistor is always driven at a source voltage that allows the amplifier's maximum output (+/-B) to be achieved. For this reason, even when the input level is low, the output stage's power loss (heat generation) is high.

The following three technologies have been developed to achieve higher efficiency in conventional power amplifier system.

• Drive Voltage Switching Amp
• PWM (Pulse Width Modulation) Amp
• SSR (Switching Series Regulator) Amp

Voltage Switching Amp

In the drive voltage switching amplifier system, the power supply voltage is switched according to the input signal level. This improves the transistor's power loss characteristics when the input signal level is low, but when the signal level becomes high it functions in the same way as a conventional system. Changes in music signal level are large and frequent, so even if the average power is low the system switches the voltage too frequently to achieve a big improvement in overall efficiency. In order to improve on this system, one can imagine a multi-stage voltage switch that increases the number of voltage changes, but more switches only serve to increase power losses and make the circuit larger and more complicated. So this solution is impractical.

PWM (Pulse Width Modulation) Amp

In the PWM amplifier system, a PWM signal is created according to the signal level of the audio signal waveform at each point in time. This arrangement results in a small power loss when output is large, making it possible to improve efficiency. However, a low pass filter must be inserted in the output stage in order to recover the original audio signal waveform from the PWM signal. This makes it impossible to avoid deterioration in the signal's frequency response, distortion, etc.

SSR (Switching Series Regulator) Amp

In the SSR system, the supply voltage is lowered to the minimum level necessary to obtain sufficient power from the amplifier by switching the SSR on and off at intervals that very according to the amplifier's output or input. In this way, the SSR's output voltage changes in accordance with the power amplifier's output voltage, so losses at the output transistor can be kept at a small fixed value regardless of whether the amplifier's output transistor can be kept at a small fixed value regardless of whether the amplifier's output value is high or low. However, since the SSR supplies the switching output waveform by leveling, it is equipped with a leveling circuit. Because of this circuit, the power supply cannot follow the steep rises in the audio signal that occur when the amplitude change is large (especially at high frequency). The results is clipping of the amplifier's output.

Switching Drive System Reduces Power Requirements

By means of a switching drive system, Yamaha's EEEngine technology reduces AC power requirements and heat loss while maintaining output power and sound quality.

Input power is supplied through a high-efficiency current buffer. During low requirement periods, it transparently switches the input power on and off automatically as needed. As the signal becomes large, an independently responding auxiliary power line supplies the additional power, as required. The output isn't compromised because the auxiliary power line is driven by the power supply voltage, which can maintain the maximum output to the speaker load. The amplifiers make more efficient use of the AC power than conventional amplifier technology.

Yamaha's EEEngine Technology incorporates the following structure:

A main power supply line that supplies driving power to the speakers. A high-efficiency current buffer combining a switching element that switches the main power supply line on and off with a leveling circuit. A control circuit that varies the on/off switching frequency according to the input signal level. An auxiliary power line that supplies power independent of the main power supply in quick response to the input signal level. A high-speed voltage buffer and current detector that adjust and control the auxiliary power supply level.

EEEngine (Energy Efficient Engine) Technology Block Diagram

This arrangement ensures efficient and highly accurate power amplification even when the input signal amplitude rises steeply.