Rotel's flagship RB-1590 power amp is conservatively rated at 350W/8ohm but achieves closer to 490W/805W into 8/4ohm in practice. Nevertheless, hugely capable though it is into these moderate impedances, the RB-1590's output into lower impedance loads is limited to 455W/2ohm and 235W/1ohm - that's just 15.3A - under dynamic conditions [see Graph 1, below]. Ordinarily it would not be unusual for a 400/500W amp to deliver in excess of 1 -2kW into low impedances. THD hovers at a consistently low 0.001-0.0016% across its full 350W range but increases with frequency from just 0.0006%/20Hz to 0.011 %/20kHz [see blue trace. Graph 2 below]. The response is wide and flat at -0.03dB/20kHz and -0.3dB/100kHz into 8ohm but with a treble roll-off that increases with decreasing load, reaching -0.8dB/20kHz and -2.5dB/100kHz into 1ohm. The ～63dB stereo separation (20Hz-20kHz) is slightly weak but, and despite the physical size of the PSU, noise is low and the A-wtd S/N ratio an impressive 92dB (re. OdBW).
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