The latest from TI called Equibit, uses a PCM-PWM converter followed by a digital amplifier stage to take digital signals directly. The output of the amp is still PWM, but before arriving at the speakers, the signal is sent through a simple LC circuit which TI calls a "demodulator" circuit. The speakers take care of the rest.

To input analog audio into these amps, you actually have to use a analog to digital converter first.

Sharp makes 1-bit digital amps (SM-SX1 and SM-SX100) that take a DSD stream as opposed to PCM. I'm not sure what they are doing to get the PWM out of the DSD, but it's probably interesting.

Stu
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If you want it to break, buy Sony!