Outboard DACs

MSB's entry-level Discrete DAC employs just two of its gold-anodised 'Prime DAC' modules, unlike the Premier product [HFN Aug '19] that features four in a dual-differential configuration. These sealed modules employ precision-matched resistor ladder networks that convert incoming 'bits' into sequential steps of current. In this R-2R, or ladder-style, DAC the LSB (Least Significant Bit) is represented by the smallest current source, with each subsequent 'bit' requiring twice the output of the last (a ratio of 1:65,536 over 16-bits). The relative 'size' of each resistor must be exact and precise if each step in conversion is to be truly monotonic, otherwise errors will occur and both linearity and distortion will suffer at low (digital) signal levels.

Rising to the challenge, each Prime DAC module includes a discrete ladder DAC that's designed, manufactured and trimmed by MSB's engineers. The partnering digital filter is a high-order linear phase type with unusually long pre/post echoes [see impulse, inset Graph]. It's executed in DSP to deliver a 30kHz cut-off for all sample rates between 88.2kHz and 768kHz, but each rate is handled separately so there are subtle differences in HF response [see inset Graph – 96kHz, black trace; 192kHz, red trace]. PM