Rotel Michi P5/S5 Pre/Power Amplifier Lab Report

Lab Report

The exceedingly powerful and yet 'gentle' sound of the S5 power amp is fully explained by the measurements. The 2x500W/8ohm and 2x800W/4ohm spec. is very conservative as the S5 actually delivers 2x670W/8ohm and 2x1.17kW/4ohm with 691W, 1.39kW and 1.78kW achieved under dynamic conditions into 8, 4 and 2ohm. A 30A current limit gives a dynamic output of 902W/1ohm [see Graph 1]. THD climbs slightly with output, from 0.0015%/1W to 0.002%/10W, 0.0027%/100W and 0.0037% at the rated 500W/8ohm (all at 1kHz). Distortion also climbs at HF, from 0.0003%/20Hz to 0.002%/1kHz and 0.016%/20kHz (all 10W/8ohm) and noise is quite low, yielding a healthy 93dB A-wtd S/N ratio (re. 0dBW). But the response is not flat, shelving down above 5kHz to reach –0.4dB/10kHz, –0.65dB/20kHz and –1.0dB/100kHz. This trend is magnified into lower loads, reaching –0.5dB/10kHz, –0.9dB/20kHz and –2.3dB/100kHz into 2ohm.

The P5 preamp offers a maximum 22.6V balanced output, clipping at vol '90' with a peak level digital input. Tested at a 6V (vol '72') the P5 offers a modest 106dB A-wtd S/N ratio, minimal ±0.1dB error in linearity over a 100dB range and very low THD – between 0.0002-0.0006% through the midrange over the top 30dB of its dynamic range, increasing to 0.001-0.006% at 20kHz [see Graph 2]. Alias rejection is merely 'average' at 69dB because Rotel has elected for the minimum phase/steep roll-off digital filter option of the AK4490EQ DAC – the impulse test showing no pre-ringing but extended post-ringing. Responses extend out to –0.2dB/20kHz, –1.3dB/45kHz and –3.9dB/90kHz with 48kHz, 96kHz and 192kHz media while its source impedance increases from 120ohm and high/mid freq. to 375ohm/20Hz (bass). PM


S5 Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 30.0A


P5 Distortion versus 24-bit digital signal level over a 120dB range (1kHz, black; 20kHz, blue)

Continuous power (<1% THD, 8/4ohm) 670W / 1170W
Dynamic power (<1% THD, 8/4/2/1ohm) 691W / 1.39kW / 1.78kW / 902W
Output imp. (20Hz–20kHz, Pre/Amp) 121-375ohm / 0.016-0.075ohm
Freq. resp. (20Hz–20kHz/100kHz) –0.23 to –0.63dB/–1.05dB
Digital jitter (USB / S/PDIF) 350psec / 370psec
A-wtd S/N ratio (DAC/Amp) 106.1dB (0dBFs) / 92.8dB (0dBW)
Distortion (DAC, 0dBFs/Amp, 0dBW) 0.0006–0.006% / 0.0003–0.016%
Power consump. (Pre/Amp at rated) 28W / 1.65kW (143W idle)
Dimensions (WHD, each unit) 485x238x465mm / 60kg (total)
Prices £3299/£5399 (pre/power)

The Rotel Co. Ltd
Tokyo, Japan
Supplied by: Rotel Europe, Worthing, UK
01903 221 710