Integrated Amplifiers

The Michi X3 [HFN Apr '21] and X3 Series 2's specifications are identical, so are there differences in the (analogue) amplifier performance? Yes... the default 0dB gain configuration now delivers a maximum +21.2dB (balanced) but there's no increase with the +1dB to +10dB settings because the volume control is inoperative from '70' to 'Max'. In practice, +21.2dB gain is more representative of a power amp than an integrated, requiring 3.48V (balanced) to raise the rated 200W/8ohm, so you'll need to check with your streamer/DAC before considering the Michi X3 S2. Otherwise, the reduced gain has improved the A-wtd S/N by ~2dB to 81.2dB (re. 0dBW), but the 2x225W/8ohm and 2x425W/4ohm power output – and 306W, 583W, 1.06kW and 1.76kW (42.0A) achieved under dynamic conditions into 8, 4, 2 and 1ohm loads – are all essentially identical to the X3 S1 [see Graph 1]. The 0.02-0.01ohm output impedance and –0.13dB response limits are unchanged but distortion is fractionally higher in the S2 at 0.005-0.035% (all re. 10W, 20Hz-20kHz).

The S/PDIF and USB ins are now handled by an ES9028PRO DAC in place of the AK4490EQ used in the X3 S1. The 107.0dB A-wtd S/N is a significant improvement over the S1, at the same 2V preamp o/p, but this is now phase-inverting. A 'fast' minimum phase digital filter has been chosen, offering an improved 76dB stopband rejection and a response that reaches out to –0.1dB/20kHz, –1.0dB/45kHz and –4.7dB/90kHz with 48kHz, 96kHz and 192kHz digital files. Jitter is a little lower at 205psec, while distortion is, again, fractionally higher at 0.0025-0.006% at the max/0dBFs output (20Hz-20kHz), falling to 0.00018-0.0016% over the top 30dB of its range [see Graph 2, below]. PM