Integrated Amplifiers

Burson Audio has specified the popular ES9039SPRO DAC (with USB-C interface) for its Conductor Voyager. This is a 768kHz/DSD1024-compatible DAC that includes seven addressable 8x digital filters which may be bypassed in their 2x and 4x stages. The final 16x IIR filter (before the SRC and noise-shaping) may also be bypassed. The Conductor Voyager enables all these bypass facilities, and even includes access to a 2nd/3rd harmonic suppression algorithm. However, while offering five of the digital filters, our unit would revert to the Minimum Phase Slow roll-off type regardless of the menu setting. This filter enjoys a much reduced ringing, traded for a non-linear group delay, a limited 8.4dB stopband rejection and treble roll-off amounting to –1.6dB/20kHz, –4.4dB/45kHz and –4.5dB/90kHz with 48kHz, 96kHz and 192kHz files, respectively. The only change occurred in ‘BP All’ mode where a ‘NOS’ impulse response was obtained.

Otherwise, the Conductor behaved as expected – the max. output from the balanced ‘DAC mode’ XLRs is a phase-positive 3.78V from a moderate 134ohm output impedance (re. 0dBFs digital input). The A-wtd S/N is a very respectable 115dB and low-level resolution is good to ±0.2dB over a full 110dB dynamic range [red trace, Graph 1]. Distortion falls to as low as 0.0002%/1kHz over the top 30dB of its dynamic range but increases to a consistent 0.004% at all frequencies over the top 10dB [see Graph 1, below]. Jitter is very well suppressed in this design to ≤12psec over all sample rates [Graph 2, below] although bursts of low-level (RFI?) noise, typically <–130dB, were also observed with high frequency signals. For a full reveal of the Conductor’s mighty headphone amplifier performance, [see boxout]. PM