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Yamaha Power Amplifier

White Paper

August 2008

Table of Contents

1. About EEEngine ...............................................................................................................2

1.1. Introduction...............................................................................................................................................................2

1.2. Explanation of different amplifier topologies ...........................................................................................................2

2. Yamaha technology..........................................................................................................5

2.1. Dual mono-amplifier structure..................................................................................................................................5

2.2. Full resonance switching power supply ....................................................................................................................5

3. Behavior of the amplifier under heavy load condition ..................................................6

3.1. Importance of stable 2 ohm load capability ..............................................................................................................6

3.2. Comparison of amplifiers at lower impedance situations .........................................................................................7

3.3. Explanation of results of listening test using music source.......................................................................................8

Summary of content (9 pages)

PAGE 1
Yamaha Power Amplifier White Paper August 2008 Table of Contents 1. About EEEngine ...............................................................................................................2 1.1. Introduction...............................................................................................................................................................2 1.2. Explanation of different amplifier topologies ...................................................................................
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1. About EEEngine 1.1. Introduction Yamaha Power Amplifier Philosophy Our approach to manufacturing power amplifiers is simple; pure and natural amplification of the input signal. Mixed audio is sent to the amplifier from the mixing console, to be amplified before final “coloring” or “flavoring” through the loudspeakers. The role of amplifiers in a sound system should not be to add its own color, but to be faithful to the input signal to give you maximum control over the final sonic performance. [ Fig.
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driven with typical program material with occasional clipping (1/8 power), Class AB topology typically achieves around 20% efficiency*, meaning that 80% of power drawn is lost as heat. Various methods have been developed to overcome this drawback which led to the development of Class H and Class D topologies. * Efficiency rate within this document refers to overall efficiency of the power amplifier including its mains power supply.
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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. [ Fig.7 ] EEEngine operational waveform EEEngine overcomes problems conventional amplifier topologies while providing advantages in all areas, offering a dramatic leap in power amplifier design.
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slew rate is however, preferable only to a point. A higher slew rate will give the amplifier a wider bandwidth, and when in excess it will ultimately result in amplification of signals even in the radio frequency range. This will waste energy, create distortion and also put undesirable stress on the speaker unit. channel amplifiers incorporating a symmetrical dual mono-amplifier design, with each mono amplifier having its own power supply.
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supplies employ what is typically called “hard switching,” which induces more noise into the DC output and gives square waveforms rich in high frequency harmonics, requiring an additional filter to remove them. “Soft switching” as seen in full resonance switching on the other hand, produces natural waveforms that are desirable for music playback. 3. Behavior of the amplifier under heavy load condition 3.1.
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3.2. Comparison of amplifiers at lower impedance situations Below are oscilloscope measurements to visualize differences in behaviors of some of the better known power amplifiers available today. The test signal is sine wave (200 cycles of 500 Hz = 0.4 sec) followed by 1.2 seconds of interval (no signal). This frequency can be found in many typical program materials, and an interval was set because continuous playback of sine waves is not realistic in actual sound reinforcement applications. [ Fig.
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[ Fig.17 ] Output signal of an amplifier, “Competitor A”. (2500W @ 2ohms) [ Fig.19 ] “Competitor C” - Rated at 3300W into two ohms, this amplifier muted quickly after its limiter kicked in. (3300W@ 2 ohms) The oscilloscope measurement on Fig. 17 shows strong compression-like behavior on its output signal. The output signal shows no resemblance of the input sine wave. This behavior was not seen when the amplifier was driven only on one channel, but quickly became unstable when driven on both channels.
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reproductions of the oscilloscope measurements. The kick drums on “Competitor A” were heavily distorted, extremely harsh on the ears and harmful to the loudspeakers as well. Its playback level fluctuated after the kick drum, as was observed in the oscilloscope measurement. The amplifier muted for a few seconds before returning. This limiter may protect the amplifier from damage, but this behavior is unacceptable in a live situation. Yamaha’s T5n showed positive results in this test.