Power Amplifiers

Rotel RB-1092 Stereo (500 Watts/Channel) Class D (Switching) Power Amplifier


On the Bench (JEJ)

We have a lot of graphs to go through here, so let's get started. For the tests, I used an Audio Precision AUX-002 switching amplifier filter, which reduces the amount of switching frequency noise getting into the Audio Precision test instrument.

At 1 kHz and 5 volts output into 8 ohms (a little over 3 watts, which is a typical listening power), THD+N was only about 0.03%.




At 4 ohms, THD+N went up a bit, but not significantly.




At 20 volts into 8 ohms (50 watts), THD+N was still low.


And at 4 ohms, still less than 0.04&perc;.


IMD was also low, only 0.004&perc; with the standard SMPTE/DIN test, using a combination of 60 Hz and 2 kHz at an output of 5 volts into 8 ohms. The test measures the resulting peaks ± 250 Hz around the upper test frequency.


At 4 ohms, IMD went up, expectedly, but it was still reasonably low.


Even at 20 volts output into 8 ohms, IMD was low, at 0.006&perc;. As the chart indicates, the amplifier needed 1 volt input to produce the 50 watts output into 8 ohms.


And at 4 ohms, less than 0.02&perc;.