Explaining the dCS Ring DAC

By: Robert Harley

THE RING DAC, invented by dCS in 1987, is a brilliant solution to the challenge of converting digital data to an analog output signal. It is particularly well suited to high-resolution digital audio.

To understand the Ring DAC, let’s first consider how a conventional multibit DAC works. You can think of a multibit DAC as a ladder, with as many rungs on that ladder as there are bits in a sample. A 24-bit DAC will have 24 “rungs,” each one a resistor that corresponds to each bit in the digital sample. The resistors are connected to a voltage source through a series of switches; the digital data representing the audio signal open or close the switches to allow current to flow to the output or not. The currents of each rung are summed, with that summed value representing the audio signal’s amplitude.

The arrangement of the resistors and the voltage source result in a “binary weighting.” This means that each resistor lower down on the rung must effectively have double the resistance of the…