Unlike other offerings in the market, the Huawei CM21 is simply a dedicated DAC/Amp with no buttons. During the review process, I have grown to appreciate the CM21 for my Huawei P20 Pro and simply adore the use of a volume knob in place of buttons implemented by other offerings.
Huawei implemented a Cirrus Logic CS43130 DAC chip in the CM21 allowing it the ability to decode audio formats of up to 384 kHz/32-bit resolution PCM, as well as native DSD decoding of up to DSD128. The CS43130 also features an integrated headphone amplifier with a maximum of 30mW @ 32Ω and 5mW @ 600Ω.
Like most USB Dongle devices, the CM21 does not feature a built-in battery and draws its power directly from the source device. During the review process, it is observed that the CM21 tends to draw more power than Huawei’s CM20 Type-C to 3.5mm audio adapter cable, especially when playing DSD files, however not significant enough to cause concern to the battery life of the source device.
Supporting UAC 2.0, the CM21 can also be used as a USB-DAC, plug-and-play on Linux, Mac OS and Windows, if your computer does not have a USB-C port, an adaptor is required. It is interesting to note that although Android also supports UAC 2.0 plug-and-play, many Android phones are still restricted at 96kHz, some even as low as 48kHz by the software implementation by the respective smartphone manufacturers. One could overcome this by using third-party software, like the Onkyo HF Player for Android. On the Huawei P20 Pro, the CM21 is able to playback HiRes Audio with a HiRes icon at the status/notification bar without the requirement of any third-party application.