Outboard DACs

The Gold represents a marked improvement over the previous Stellar DAC [HFN Apr '20]. Gone are the idiosyncratic 'Gain Cell' modules to be replaced by a fully discrete, balanced Class A preamp capable of delivering a full 4.08V from a moderate 188ohm source impedance. The older ES9018 DAC is replaced by an ES9038PRO in the Gold, this single 8-DAC chip operated in double-differential mode to deliver a wide 116dB A-wtd S/N ratio with THD held to just 0.0003-0.0006% at peak (0dBFs) output, falling to a minimum of 0.00008-0.0002% (all re. 20Hz-20kHz) over the top 20dB of its dynamic range [see Graph 1, below]. There are mere ±0.3dB errors in low-level linearity over a wide 110dB dynamic range while the dual-mono analogue layout confers a wide 129dB channel separation. However, some low-level 'warbles' are present, deep in the noise floor, as interference from – I presume – the PIC microcontroller or other housekeeping logic. These are visible, averaged over time, as 'waves' in the jitter spectrum [see Graph 2] which otherwise illustrates some ~140psec of PSU-induced sidebands.

Frequency response, and stopband rejection, are a function of sample rate and choice of digital filter. The Linear and Min. Fast filters offer the flattest responses of –0.3dB/20kHz, –0.1dB/45kHz and +0.25dB/90kHz with 48kHz, 96kHz and 192kHz media, respectively, trading this, and good 83dB/75dB stopband rejection(s), for more aggressive ringing. Of the seven filters included in the ES9038PRO DAC, PS Audio's default is Minimum Slow. This has very little 'ringing' but a reduced 18dB stopband rejection and a rolled-off treble at –5.0dB/20kHz, –7.0dB/45kHz and –6.8dB/90kHz. It is ideally suited for 96kHz+ music files. PM