Outboard DACs

Lab Report
Violectric has specified Cirrus Logic’s CS43131 DAC (with USB-C interface) for the DHA V226 and various of its digitally-equipped pre/headphone amplifiers. This is a 384kHz/DSD256-compatible DAC that includes five addressable digital filters – linear phase, minimum phase and NOS types – of which Violectric has chosen the fast roll-off minimum phase option. This filter avoids the pre-ringing of a linear phase filter, traded for a non-linear group delay, but offers excellent stopband rejection of >96dB and 24dB with 48kHz and 96kHz media, respectively. Responses are flat and extended to within a tight ±0.02dB from 20Hz-20kHz and with sharp cut-offs of –1.4dB/45kHz and –3.0dB/ 90kHz with 96kHz/192kHz files, respectively. The underlying response of the pre/headphone amp is flat to within ±0.02dB (10Hz-100kHz)!

Maximum output from the single-ended preamp RCAs is a phase-positive 4.7dBV (1.72V) from a peak 0dBFs digital input – these outputs are not included in the ±18dB preamplifier section but still benefit from a vanishingly low 0.15ohm source impedance. The A-wtd S/N is a still-respectable 107.5dB, despite the reduced output, while low-level resolution is good to ±0.4dB over a full 110dB dynamic range. Distortion falls to as low as 0.000013%/1kHz over the top 10dB of its dynamic range but is ~30dB higher at 20kHz over the top 50dB of its range, after which there is a step reduction in 2nd/3rd harmonics and ultrasonic noise. Jitter is very well suppressed in this design with only a suggestion of low-rate phase noise seen as a broadening at the base of the J-test signal. Correlated jitter is typically <10psec across all sample rates.

Dist. vs. 48kHz/24-bit digital signal level over a 120dB dynamic range (1kHz, black; 20kHz, blue

High-resolution 48kHz/24-bit jitter spectrum shows some phase noise but no correlated sidebands