oh this is neat, apparently the yamaha dx7 achieved its 15-bit digital audio by using a 12-bit DAC and wiring a 3-bit DAC (actually an 8-to-1 analog multiplexer with a resistor ladder on its inputs) into its reference voltage.
it also ran the DAC at 800 kHz and multiplexed its output across sixteen voices for an effective 50 kHz per voice
-F
@Felthry That's pretty ingenious