Audiophilepure

https://hometheaterhifi.com/reviews/audio-player/portable-audio/astellkern-kann-cube-digital-audio-player-and-billie-jean-iem-review/

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There are no user-selectable digital filter options for the Astell&Kern KANN CUBE. The above digital filter test is based on a protocol suggested by Jurgen Reis of MBL Audio. This noise test shows the characteristics of a sharp filter that is flat to 22 kHz (with a 44k sample/sec input) with a steep roll-off thereafter. The reconstruction tone of a 19KHz signal is down 65dB. This is as it should be. Some products have filters that can produce a high-end droop and minimal rejection of the 19kHz reconstruction tone.

All in all, from an objective standpoint, the Astell&Kern KANN CUBE produces impressively low THD+N numbers and has excellent linearity characteristics. One should have no qualms using it as a source component in a high-end stereo system let alone in its intended portable use.”