Outboard DACs

Lumin's 'Analogue Audio Resampling' is entirely synchronous, so 48kHz inputs have the option to be upsampled to 96kHz, 192kHz and 384kHz while 88.2kHz streams may be lifted to 176.4kHz and 352.8kHz, for example. The impact on distortion is measurable but negligible – actually slightly higher with upsampling – but THD is otherwise as low as I have seen from the ES9028PRO DAC at 0.00005%/1kHz up to 0.00035%/20kHz at the D3's peak 0dBFs/5.03V balanced output [see Graph 1, below]. This is significantly lower than achieved by the WM8741 DACs employed in the Lumin D2 [HFN Jul '20] although the very wide 116.5dB A-wtd S/N ratio and low 10ohm source impedance reflect the similarities in the D2/D3's analogue output stage(s).

But here's where Lumin's upsampling does have a real impact because the A-wtd S/N improves still further to 118.5dB – clearly visible on the jitter spectrum [see Graph 2] – along with a reduction in correlated sidebands from 65psec to 10psec (48kHz native vs. upsampled to 192kHz). Format conversion to DSD64 results in an increase in jitter to 165pec alongside the expected lift in top-end noise [green spectrum, Graph 2] but this falls back to 37psec when converted from 48kHz to DSD128. Meanwhile, although Lumin's chosen filter for the ES9028PRO DAC – the slow roll-off linear phase option – remains in the loop, the responses are still influenced by upsampling. At higher sample rates the top-end response switches from –6.6dB/45kHz to –9.4dB/45kHz (96kHz media) and –15.4dB/90kHz to –19dB/90kHz (192kHz media) with upsampling off (native) then switched on, respectively. Plenty here for the 'fine-tuners'! PM