The Future of Audio Amplification

Laptop chargers, battery chargers, TV's, you name it.

-Which don't draw any more power than the Berning TF-10, FWIW. I had a USB power supply fail on me when I took it on the Grand Divide Mountain Bike Route, but that was likely due to vibration more than anything else- the Tour Divide (as its known) has a way of doing that.

You can mess up any amplifier operating class. The specific implementation is more important.
Class A implies better quality than D or inverse F, but that "class" system is not a value scale.
Class A sets the zero signal in the middle of the operating range, as to avoid the typical non-linearities at the extremes of the device's transfer curve. This was in started in the tube age. Many later semiconductor devices had poor linearity, which was "fixed" with gobs of feedback, and transistor power amplifier output stages almost exclusively have no gain, they just operate as voltage followers/current amplifiers. So linearity biasing is not the goal here, but avoiding ugly transitions when the voltage crosses the zero point. 
There would be more work getting a D amp to perform well, but of course as this thread has shown it is possible. The digitizer must be very good, operating at a high frequency and have good filters for the output. Higher frequencies will be easier to filter out and will have more resolution. 
The bit stream output from a DAC could be used to drive an output stage, perhaps skipping some time middle pieces. Change the power supply voltage and the gain changes. 
Obviously junk in the power supply will end up in your ears.

@atmasphere 

How do you figure? A laptop charger outputs several amp. It has to charge 6 or 8 3000mAh batteries in a couple of hours. Ain't no solid state pre-amp on the planet that has those kinds of power demands. 

@kosst_amojan
The Berning TF-10 is a tube preamp with about 10 tubes in it. It draws about 60 watts; that's about the same as my laptop charger.

Panasonic came out with a new formula for electrolytic capacitors some years back that allowed them to be a lot smaller with good performance. Chinese copies of that part proved to be unreliable but due to their price found their way into a lot of consumer gear- laptops, chargers, that sort of thing. So I've become hesitant to blame electrolytics for failures generally speaking, until I know more about the actual part used. If its one of those knock-offs, its going to fail no matter what.

Funny, I haven't read anyone comment about having owned both class d and a-a/b. I'm very interested in what they think. This thread, as well as the entire audiogon forum, is populated with either/or, one or the other, with very strong advocates in both camps.