I performed a complete set of measurements on the WiiM Amp with my Audio Precision SYS2722 system.1 Before I did so, I installed the WiiM Home app on my iPad mini and connected the amplifier to my network with a CAT-5 Ethernet cable. The app (version 2.9.5.24041612) recognized the Amp, and I performed a factory reset.
Because the amplifier has a class-D output stage, I inserted an Audio Precision AUX-0025 passive low-pass filter between the test load and the analyzer. This filter mitigates noise above 80kHz and eliminates noise above 200kHz that would otherwise drive the SYS2722’s input circuitry into slew-rate limiting. Without the filter, 470mV of ultrasonic noise with a center frequency of 460kHz was present at the amplifier’s output terminals. I used the Audio Precision filter for all the tests other than frequency response. Because
