Outboard DACs

Is this a textbook implementation of the ESS Sabre 9038 DAC? Well, yes, but not without a suggestion of panache (colour) that distinguishes the AAdac from the host of other ES9038 solutions on the market. Distortion is very low indeed and also consistently so at ~0.0005% or less over the top 30dB of its dynamic range from 20Hz-20kHz [see Graph 1]. This is a function of the DAC and also the excellent overload/slewing performance of the fully balanced analogue stage that delivers a maximum 3.475V from a moderate 46ohm source impedance at just 0.00045%/20kHz. The A-wtd S/N ratio is a wide 114dB too – via USB and S/PDIF inputs – while low-level linearity is within a tight ±0.04dB/ –100dBFs and just ±0.2dB over a full 110dB range. Jitter is inherently well suppressed by the ES9038 DAC's firmware so the 100-250psec of ±100Hz, +200Hz, etc, sidebands measured here may be either PSU-induced jitter or PSU-related IM distortion [see Graph 2, below]. In any case, the subjective impact – a very minor and often pleasing warmth at LF – will be the same.

Now to those seven digital filters... In the absence of a manual or online specification, I have identified the built-in ESS options as follows (in anti-clockwise LED order around the main dial): Brickwall; Corrected minimum phase fast; Apodising Fast; Minimum phase slow; Minimum phase fast; Linear phase slow and Linear phase fast. The 'Slow' options trade a greatly reduced transient ringing for an earlier HF roll-off (–5dB/20kHz Minimum, –3.5dB/20kHz Linear phase) and poorer stopband rejection (18dB Minimum, 14dB Linear phase) and are better used with 96kHz+ sample rate inputs. The Brickwall and 'Fast' filters offer >75dB stopband rejection and very flat (–0.1dB/20kHz) responses albeit with more extensive ringing. Take your pick! PM