What is the reason for classd?

What is the meaning of classd amplification? We all know the answer, it is the increased efficiency which allows us to make smaller amplifiers which consume less energy. The challenges when designing a switching amplifier are tremendous compared to designing a linear amplifier. A major distortion contributor is usually the transition time variation which causes both even and odd harmonics. A way to minimize it is to tune the dead time to a minimum but this leads to more losses and what was the reason for classd again? Is there a point of using classd if the idle losses are as high or even higher than a high quality linear amplifier? Of course, having high efficiency at intermediate or high output powers is always useful to allow for a smaller heat sink and/or lower temperatures but since most amplifiers generate very low output powers most of the time, the idle consumption is key for saving energy. Audio Bricks designs all the bricks for minimizing the losses, especially at idle. Engine-400 as an example, consumes 3W at +/-55V including VA+/- and VDR (2,2W from +/-55V) which corresponds to 0,75% of the rated 400Wrms into 4ohm at that rail voltage. A typical linear amplifier stage is usually biased at 50-100mA in the output stage plus another 15mA in the driver and input stage giving a total of up to 12W.

Category: Classd
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