Outboard DACs

There are clear comparisons between the M8x DAC and Musical Fidelity’s Nu-Vista DAC [HFN Mar ’24], both of which are based around the same ES9038Q2M-based circuit. The M8x DAC is solid-state throughout, of course, with a lower 0.0001-0.0004% distortion (re. 20Hz-20kHz, 0dBFs) at the same 4.1V maximum output, albeit phase inverted. THD falls even lower over the top 20dB of its dynamic range to 0.00008-0.00017% [see Graph 1], better reflecting the potential of the ES9038 DACs with nuvistors ‘out of the circuit’. That said, the A-wtd S/N ratio is unchanged at 101.4dB [see boxout] while the source impedance is a flatter 96ohm (re. 20Hz-20kHz). Jitter is exceptionally low at <8psec via all sample rates and is unaffected by either the ‘reclocking’ or ‘upsampling’ modes. The responses, meanwhile, are determined by your choice of digital filter which, in turn, are only enabled once the ‘upsampling/oversampling bypass’ option is switched off. The latter mode causes the M8x to clip with 0dBFs (full digital scale) inputs and should probably be avoided.

The digital filters [see Graph 2] include four linear phase types that offer a constant group delay, yielding a time-coherent output, and two minimum phase options that free the impulse response of any unnatural, acausal pre-ringing but increase post-ringing and incur a non-linear group delay. Linear phase fast [black] offers responses out to –0.05dB/20kHz, –0.2dB/45kHz and –1.4dB/90kHz with 48kHz, 96kHz and 192kHz files, and a stopband rejection of 83dB. Minimum phase [red] trades a mere 18dB rejection for limited ringing and responses of –5dB/20kHz, –2.2dB/45kHz and –8.1dB/90kHz. Hybrid [blue] reaches –12.3dB/20kHz, –23dB/45kHz and –25dB/90kHz, respectively. PM