Integrated Amplifiers

The object of this lab report is not only to answer the question 'does the RA-1592MKII meet its specification?' but, more intriguingly, 'does this perform like a Michi X3 [HFN Apr '21] in a lower-cost case?'. The answer to both questions is 'yes, most definitely!'. Like the Michi X3, the RA-1592MKII is rated at 200W/8ohm and succeeds in delivering 2x225W and 2x425W at <1% THD with sufficient headroom to support an identical 307W, 585W, 1.08kW and 1.76kW (41.9A) into 8, 4, 2 and 1ohm loads under dynamic conditions [see Graph 1]. Similarly, gain is uncommonly low at just +24dB, allowing better use of the volume control with today's (balanced) line-level sources. The A-wtd S/N ratio is 1dB wider than the X3's, but still below average at 80.7dB, while the output impedance is fractionally lower via the RA-1592MKII at 0.029-0.042ohm (vs. 0.025-0.11ohm re. 20Hz-20kHz) and the response slightly flatter at –0.1dB/20kHz to –0.5dB/100kHz (vs. –1.0dB/100kHz). Distortion is unchanged at 0.0013-0.018% (10W/20Hz-20kHz), the trend, again, broadly consistent across a 1W-200W/8ohm output.

The RA-1592MKII and X3 diverge at the DAC/preamp stage, the latter offering a superior performance. Instead of the X3's AK4490EQ DAC with steep minimum phase digital filter, the RA-1592MKII uses a TI DAC with a short linear phase filter that offers a limited 44dB stopband rejection but very flat response out to –0.05dB/20kHz, –0.6dB/45kHz and –1.3dB/90kHz with 48kHz, 96kHz and 192kHz media. Jitter is a little poorer at 675psec but the 103dB A-wtd S/N and ±0.3dB/100dB linearity are comparable. Finally, THD is uniformly higher (eg 0.0036-0.017%, max/0dBFs output, 20Hz-20kHz) [see Graph 2, below]. PM