Integrated Amplifiers

In practice, WiiM’s choice of TI’s PurePath Class D amplifier module [see Lab Report, p75] brings it closer to the likes of HiFi Rose’s RS201 E streamer/amplifier [HFN Mar ’22] than competitors using ICEpower’s latest ‘Edge’ technology or anything from the self-oscillating Hypex/Purifi/Eigentakt platform. As a result, the WiiM Amp retains some familiar foibles of ‘traditional’ analogue Class D amplifiers where the module’s inductive output filter causes a rise in output impedance at high frequencies, lifting from a ‘flat’ 0.064ohm (20Hz-1kHz) to 0.43ohm/10kHz, 1.7ohm/20kHz and 28ohm/50kHz [red trace, see Graph]. This means changes in loudspeaker load impact both distortion and response.

Unloaded, with a 192kHz digital input, the Amp has a significant resonance/response peak of +28dB/50kHz [grey trace, see Graph]. Into 8ohm [black trace] it rises to +0.9dB/20kHz before peaking at +3.4dB/48kHz, but rolls away into 4ohm to –0.5dB/20kHz [orange] before drooping further to –3.1dB/20kHz into 2ohm [blue] and –6.8dB/20kHz into 1ohm [green]. So the high treble ‘character’ of the WiiM Amp may also depend on your choice of partnering loudspeaker. PM