Outboard DACs

With its dual ES9039Q2M DACs, 4.3V balanced output and neat production engineering, the Preciso has all the makings of a very high-value, high performance unit. Volumio publishes a THD+N spectrum on its website showing 0.000074% at 1kHz/ 0dBFs, but the 3rd harmonic was fractionally higher from our sample at 0.00016%. That said, distortion falls to 0.00003% over the top 20dB of its dynamic range [see Graph 1]. But some extra polish and QC is required – the L/R channels were reversed in our box, the sample rates were misreported with S/PDIF, and digital filters #1-8 defaulted to the slow/minimum phase (#4) option regardless of setting.

The USB input provides correct access to the digital filters which include #2 (slow linear phase) and #4 (slow minimum phase), both trading a poor ~7dB stopband rejection and early treble roll-off (–4.1dB/20kHz, –5.3dB/45kHz and –6.1dB/90kHz with 48kHz, 96kHz and 192kHz inputs) for much reduced time domain distortion. By contrast, #1 (fast linear phase) and #3 (fast minimum phase) offer >120dB stopband rejection and flat responses (–0.06dB/20kHz, –0.6dB/ 45kHz and –1.4dB/90kHz with 48kHz, 96kHz and 192kHz inputs), albeit with a more pronounced time domain ‘ripple’.

Volumio also makes mention of a ‘single high-accuracy MEMS clock driving both DACs’ although the Preciso still exhibits a high-level, low-rate (±10Hz) jitter of 4000-5000psec with all sample rates and digital inputs. The USB-B input also shows an extended PSU-related jitter [black, Graph 2] that is absent with the same 24-bit data via the S/PDIF input. Otherwise, the 116.5dB A-wtd S/N ratio is excellent, as is the ±0.3dB resolution over a full 110dBFs dynamic range. As I say, there’s potential here. PM