Gear & technology
R2R/ladder DAC
Also called R2R, ladder DAC, multibit DAC, resistor ladder
An R2R, or resistor ladder, DAC converts each sample directly through a network of precisely matched resistors, one step per bit. It was the original way to build a DAC and has returned as a boutique alternative to delta-sigma chips.
Each bit switches its leg of the ladder between the reference voltage and ground, and the ladder weights each bit by half the one before, so the output voltage is the binary-weighted sum. The approach is simple in concept and hard in practice: the resistors must match to a few parts per million, which is why discrete R2R DACs from makers such as Denafrips and Holo Audio cost more than delta-sigma designs.
Supporters describe a more natural, less "digital" sound, especially when the DAC skips oversampling and filtering, a mode called NOS. Measurements usually show higher distortion and noise than a good delta-sigma design, so the debate is a clear case of preference against figures. Listeners disagree.