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Old 17th May 2020, 2:16 pm   #1502
Craig Sawyers
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Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,942
Default Re: The Audiophoolery Thread.

The only thing that class A (and class D for that matter) is no crossover distortion. But efficiency for class A is dire. For 100W into 8 ohms pure class A needs a standing current of 2.5A. With +/-45V rails that is a standing power dissipation of 225W per channel. So on a programme average level of 2W (which is typical) the Self 1% efficiency is about right. On programme peaks and transients of course the power will be much higher.

Self's position on subjectivism is well known. I have all his books, because there is a lot of sense in them. And Self in his role as design consultant has produced some landmark designs. But he does bang on a bit in the first chapter. Let's not forget that he was historically vocally against capacitors degrading sound quality, until he measured the distortion introduced by polyester capacitors, that they "ran in" with distortion reducing over time and remembered the running in behaviour.

At least he has the good grace to admit when he was wrong.

Of course most of the original material for the Blameless principle in the Power Amplifiers book, he originally published in eight articles in Wireless World in late '93 to early '94. So 26 years ago, including the term "blameless".

He has refined the Blameless class B designs a bit since '94, but not by a massive amount.

Craig
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