Yamaha @PET RP-U100 personal receiver Measurements part 5
Fig.14 Yamaha RP-U100, distortion (%) vs continuous output power into (from bottom to top) 8 ohms, 4 ohms, and 2 ohms.
Fig.15 Yamaha RP-U100, distortion (%) vs 1kHz-burst output power into 8 ohms (black trace), 4 ohms (red), 2 ohms (blue), and 1 ohm (green).
Less power was available in the bass on this test (54.3W at 50Hz into 4 ohms), but, given its nearfield listening use, it's hard to imagine the Yamaha being bothered by any real loudspeaker load. Certainly it worked very well with the Evett & Shaw speakers I used, which dip to just 1.2 ohms between 400Hz and 500Hz.
Considering how little it costs and how many features it offers, the RP-U100 measures surprisingly well, particular regarding its output amplifier stage. Achieving good sound at this price level is all about the product's designers engineering appropriate compromises, and this Yamaha appears to have done.—John Atkinson