Rogers Ravensbourne Stereo Lab Report

As discussed in our review, the Rogers Ravensbourne is unusual - for the era - in being DC-coupled at the output, relying on a a series of manual presets to manage any offset at the speaker terminals. This takes a short time to stabilise so I would advise speakers not be connected for the first five minutes after switch-on, allowing DC levels to reduce from ~750mV to a final (low) 4mV. DC-coupled or not, the bass response is 'pre-filtered', peaking at +1dB/25Hz before rolling steeply away to -1.8dB/20Hz and -30dB/11Hz. The top-end response is well extended, again for the era, to -1dB/20kHz and -8dB/100kHz, while the 'Slope' control offers a 20kHz notch of -16dB (mid position) and -35dB (full position) when set in the '9kHz' mode. This is ideally set to null an FM pilot tone, for example, while its severity (slope) can be tuned against its impact on the perceived brightness of HF detail. The 0.47-1.05ohm output impedance (20Hz-20kHz) will also exert some influence on system response according to the uniformity of the attached loudspeaker load.

Rogers rated this smart-looking amplifier at 2x25W/8ohm via its 8/15ohm connection and this was met into 8ohm despite falling to 2x13W/4ohm. There is sufficient headroom to accommodate 43W, 29W, 16W and 8W into 8, 4, 2 and 1ohm loads, respectively, under dynamic conditions [see Graph 1] but this is still no powerhouse. Rogers also claims that its 36dB feedback reduces distortion from 3% to 0.05% at 10W output and this is largely true through the midrange [see Graph 2, below] although it increases to 0.85%/20Hz and 1.85%/20kHz. Otherwise, the 75dB A-wtd S/N ratio (re. 0dBW) is on target, but low by modern standards, as is the >37dB stereo separation. PM

Rogers Ravensbourne Lab 1

Dynamic power output vs. distortion up to 1% THD into 8ohm (black trace), 4ohm (red), 2ohm (cyan) and 1ohm (green) speaker loads. Max current is 2.83A

Rogers Ravensbourne Lab 2

Distortion versus frequency from 20Hz-20kHz at 1W/8ohm (black) and 10W/8ohm (red)

Power output (<1% THD, 8/4ohm)26W / 13W
Dynamic power (<2% THD, 8/4/2/1ohm)43W / 29W / 16W / 8W
Output imp. (20Hz-20kHz/100kHz)0.47-1.05ohm / 5.68ohm
Freq. resp. (20Hz-20kHz/100kHz, 0dBW)-1.8dB to -0.95dB/-7.9dB
Input sensitivity (for 0dBW/25W)32mV / 159mV
A-wtd S/N ratio (re. 0dBW/25W)74.7dB / 88.7dB
Distortion (20Hz-20kHz, 10W/8ohm)0.055-1.85%
Power consumption (Idle/rated output)18W / 90W
Dimensions (WHD, inc case) / Weight378x149x290mm / 7.9kg