The 2.1 amplifier in question could have turned out to be an excellent product were it not for an annoying mid-high frequency hum audible at low volume on the left and right channel speakers. At high speed the tone on the subwoofer is quite satisfactory.
The amplifier is producing a weird hissing noise. Even when the volume is at 0. Tried different power adapters, with and without speakers connected, but the weird hissing sound remains. The higher the amperage of the adapter, the louder the hissing noise. It's coming from the PCB. It kind of sounds like the components are under a lot of strain. It's unuseable since it's very noticeable when there's no music playing. Throwing it away. Too bad.