Integrated Amplifiers

If your loudspeakers are either insensitive or present a cruel load then Rotel's Michi X3 is almost 'Hobson's Choice' at sub-£5000. Rated at 200W and 340W into 8/4ohm, respectively, it succeeds in delivering 2x225W and 2x425W at <1% THD with sufficient headroom galvanised by that huge PSU to support 307W, 585W, 1.1kW and 1.78kW (42.1A) into 8, 4, 2 and 1ohm loads under dynamic conditions [see Graph 1, below]. Gain is rather lower than specified at just +24dB but allows full use of the volume control with today's 4V+ (balanced) line level sources. The A-wtd S/N ratio is also below average at 80dB, albeit from a subjectively pleasing white noise than any hum from that custom toroidal transformer. Output impedance is usefully low at 0.025-0.035ohm (20Hz-5kHz) while the response reaches out to ±0.1dB from 20Hz-20kHz (and –1dB/100kHz). Finally, distortion is also low at 0.0013–0.021% (20Hz-20kHz) and tracks this trend consistently from 1W-200W/8ohm output.

Measured via the preamp RCAs at 2V output (the internal power amp clips at much above this level) the S/PDIF and USB inputs are all routed via a default, steep minimum phase digital filter that has long post-echoes, a moderate 69dB stopband rejection but a very flat response that reaches out to –0.05dB/20kHz, –0.7dB/45kHz and –1.6dB/90kHz with 48kHz, 96kHz and 192kHz digital files. Jitter is acceptable at 250psec, the A-wtd S/N, again, slightly lower than expected at 103dB but low-level resolution remains true to a tight ±0.2dB over a 100dB dynamic range. While distortion is a low 0.0015-0.0045% at max/0dBFs output (20Hz-20kHz), it falls lower still to 0.0003-0.00056% at –15dBFs [see Graph 2, below]. PM