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<blockquote data-quote="ahole-ic" data-source="post: 7551459" data-attributes="member: 619324">Class a/b is usually 50-60% efficient. Anything else said is simply untrue. If they were similar efficiencies, there would be absolutely no reason to go with a class d vs a/b since you have degraded signal with class d. Class d amplifiers are usually ~70% efficient and up. The lower the impedence on a class d, the less efficient it becomes. Some companies pad the efficiency rating by using a really high impedence. Don&#039;t be fooled.&quot;Theoretical power efficiency of class D amplifiers is 100%. That is to say, all of the power supplied to it is delivered to the load, none is turned to heat. This is because an ideal switch in its on state will conduct all current but has no voltage across it, hence no heat is dissipated. And when it is off, it will have the full supply voltage standing across it, but no current flows through it. Again, no heat is dissipated. Real-life power MOSFETs are not ideal switches, but practical efficiencies well over 90% are common. By contrast, linear AB-class amplifiers are always operated with both current flowing through and voltage standing across the power devices. An ideal class B amplifier has a theoretical maximum efficiency of 78%.&quot;<a href="http://en.wikipedia.org/wiki/Class-D_amplifier" target="_blank">http://en.wikipedia.org/wiki/Class-D_amplifier</a>You can see there that it&#039;s easy to fudge the numbers and make them seem similar, but in reality class d is ~25% more efficient than class a/b.</blockquote>

[QUOTE="ahole-ic, post: 7551459, member: 619324"] Class a/b is usually 50-60% efficient. Anything else said is simply untrue. If they were similar efficiencies, there would be absolutely no reason to go with a class d vs a/b since you have degraded signal with class d. Class d amplifiers are usually ~70% efficient and up. The lower the impedence on a class d, the less efficient it becomes. Some companies pad the efficiency rating by using a really high impedence. Don't be fooled. "Theoretical power efficiency of class D amplifiers is 100%. That is to say, all of the power supplied to it is delivered to the load, none is turned to heat. This is because an ideal switch in its on state will conduct all current but has no voltage across it, hence no heat is dissipated. And when it is off, it will have the full supply voltage standing across it, but no current flows through it. Again, no heat is dissipated. Real-life power MOSFETs are not ideal switches, but practical efficiencies well over 90% are common. By contrast, linear AB-class amplifiers are always operated with both current flowing through and voltage standing across the power devices. An ideal class B amplifier has a theoretical maximum efficiency of 78%." [URL="http://en.wikipedia.org/wiki/Class-D_amplifier"]http://en.wikipedia.org/wiki/Class-D_amplifier[/URL] You can see there that it's easy to fudge the numbers and make them seem similar, but in reality class d is ~25% more efficient than class a/b. [/QUOTE]

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