Integrated Amplifiers

Its quartet of substantial feet lift the H390 sufficiently off the deck that the meatiest of audiophile hands can still reach the on/off rocker switch located beneath. Discount those pins and the H390 is uncommonly svelte for what is a hugely capable design. In practice, it delivers in excess of its 250W/8ohm rated output to the tune of 2x270W/8ohm and 2x490W/4ohm with 279W, 544W, 1.04kW and 1.16kW available at <1% THD under dynamic conditions into 8, 4, 2 and 1ohm loads [see Graph 1, below]. This power is delivered through a low 0.014-0.048ohm source impedance and a response that's flat to within –1dB from 6Hz-75kHz (–1.6dB/100kHz). Noise is very low too, the H390 matching the H590's sensibly 'low' +32.6dB gain (balanced inputs) and contributing to a generous 90dB A-wtd S/N ratio (re. 0dBW). Distortion is equally low and climbs only gently with increasing output from 0.0022%/1W to 0.003%/10W, 0.008%/100W and 0.015%/200W through bass and midrange. Versus frequency, THD increases beyond 5kHz although it still only reaches 0.02%/20kHz at 10W/8ohm.

The digital board, based on the H590, features the same AKM AK4490 DAC with its minimum phase/fast roll-off filter. Distortion is just 0.0004-0.0028% (20Hz-20kHz, 0dBFs), with a minimum of 0.0001% [see Graph 2, below] and with response limits of +0.1dB/20kHz, +0.3dB/45kHz and +0.5dB/55kHz (to –1.7dB/90kHz) with 48kHz, 96kHz and 192kHz media, respectively. The fixed preamp offers 2.43V from a high 951ohm source impedance, but the 106dB A-wtd S/N ratio is creditable. With all digital inputs routed through via the USB DSP section here, jitter is fabulously low at <10psec with all sample rates. PM