DacMagic's Filters

The DacMagic’s 32 bit DSP runs Cambridge Audio’s own proprietary digital filter algorithms with three different filter options available: Linear Phase, Minimum Phase and Steep. Controlled from one switch on the front panel, they are extremely clever audiophile topologies specifically developed for audio playback and all offer excellent sound quality but differ slightly to appeal to a wide range of listening tastes.

Linear phase is the same as used in the flagship Azur 840C upsampling CD player. It uniquely features ‘constant group delay’ which delays all audio signals at all frequencies by the same amount meaning all audio is fully time-coherent at the output.




Minimum phase meanwhile does not feature constant group delay but rather the co-efficients have been optimized without feed-forward so that the impulse response exhibits no pre-ringing in the time domain. Some commentators have argued that the pre-ringing as seen in nearly all digital filter designs may affect the transient attack of percussive instruments. Minimum phase implementation eliminates this and is a technology only seen previously in some extremely highend CD playback systems.


Lastly, the steep filter removes close in aliasing artefacts by re-calibrating the co-efficients for a very slight roll off at 20kHz but an ultra steep drop to the stop-band just after 20kHz.

These three filters are all of the highest quality but offer subtle differences for the user to enjoy. The type of filter chosen is remembered for each input individually so that it is possible to use one for PC playback via USB and another for CD playback via SPDIF.