I looked at a random TI headphone amp chip [1] for portable gaming systems. It's tiny (3mm×3mm) and uses CMOS for low power consumption. Internally it has a charge pump to generate the voltages it needs from a wide power supply range. The charge pump also allows the output to be centered around ground so DC blocking capacitors can be omitted. The chip includes click and pop suppression. Inexplicably it is Windows Vista compliant. So audio chips have progressed a lot since this Nintendo chip.