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

620rotel.lab1

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

620rotel.lab2

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)

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