Pre/Power Amplifiers

The published specification for Onkyo's M-80 differs by territory but for the UK it is rated at 150W/8ohm, with a –3dB response limit of 100kHz, and no formal numbers given for distortion. So how does the M-80 perform against its peers? In practice it delivers 2x175W/8ohm and 2x270W/4ohm (re. 1% THD at 1kHz) while the PSU has sufficient in reserve to accommodate an increased 248W, 469W, 760W into 8, 4 and 2ohm loads, respectively, under dynamic conditions [1kHz/10msec to 1% THD, see Graph 1 below]. Output into 1ohm is protected at 250W but the maximum 19.5A current capacity will still be sufficient to wrestle with most likely partnering loudspeaker loads. The frequency response, meanwhile, meets expectation at +0.0dB to –0.2dB (20Hz-20kHz) and –3.2dB/100kHz (all re. 10W/8ohm), while the relatively flat 0.1-0.14ohm output impedance (20Hz-20kHz) will cause some further slight modification of the amp/speaker system response where the load impedance is both tough and quite variable.

The M-80's output stage is not especially richly biased so distortion is highest at low power, decreasing thereafter from 0.02%/1W to 0.008%/10W and 0.002%/100W before rising again to 0.03% at the rated 150W (all re. 1kHz/8ohm). This trend broadly holds with frequency [see Graph 2], reaching a minimum of 0.0016%/300Hz and increasing to 0.01%/20Hz and 0.013%/20kHz [all re. 100W/8ohm; red trace, Graph 2]. Hum is low and the A-wtd S/N ratio above average at 88.5dB (re. 0dBW) while the overall gain via the balanced XLR inputs is a sensible +22.5dB, requiring 2.6V to raise the rated 150W/8ohm. And the meters? The needles accurately represent power into 8ohm. PM