Once properly configured the DacMagic Plus performed perfectly throughout the review period. But the DacMagic does have one ergonomic quirk: its volume control. Unlike most volume controls, which are in some way directly connected to an attenuator, the DacMagic Plus control is more like a switch. When you turn it, it feels loose and sloppy before it engages. Once engaged, it takes a moment for the volume knob to respond. To some prospective users this volume control will feel cheap. But the reason the volume control feels the way it does is because it isn’t an analog or bit-reduction digital controller but a DSP driven digital domain gain stage using Anagram Q5 adaptive time filtering to accomplish gain reduction without bit-reduction.
With no dots, numbers, or indicators to tell a user what the relative volume level is, doing repeatable, matched-level comparisons between inputs with different levels was nearly impossible. Some potential users will not care for the volume knob’s feel and lack of level calibration, but for normal everyday use I didn’t find they were a serious issue.
The DacMagic Plus offers three different digital filter settings that can be changed via a front panel button: linear phase filtering, minimum phase filtering, and steep filtering. According to Cambridge Audio, “The Linear Phase filter is a highly regarded audio filter offering low ripple in both the pass and stop bands, and what is known as constant group delay. Constant group delay means that audio signals of all frequencies are always delayed by the same amount when passing through the filter. All audio is therefore fully time-coherent at the output. The trade-off with this type of filter is that due to internal feed-forward in the DSP, its impulse response will exhibit some pre-ringing.” The minimum phase filter “offers even lower ripple in the pass and stop bands. Unlike the Linear Phase filter, group delay is not constant so some time coherence is lost; however, phase shift is low and the particular benefit with this filter is that the impulse response exhibits no pre-ringing.” Finally the Steep filter “is a linear phase filter that has been optimized for stop band attenuation of close-in aliasing images. Here we have traded a little attenuation of the very highest frequency response (-2dB at 20kHz) and a little more pre- and post-ringing for a very steep attenuation just outside the pass band. The Steep filter is able to attenuate aliasing at 22kHz by some 80dB.” Cambridge Audio encourages users to experiment to hear which filter setting sounds best with different material. Each input can have a different filter setting so when a given input is selected a particular filter will be employed.
The DacMagic Plus includes one more adjustable sonic parameter: absolute phase. If a user holds down the digital filter button for more than a second it becomes the phase switch so you can go from positive phase to inverted phase. For those who haven’t heard of a phase switch before, it’s not the same as the phase button found on early stereo gear, which switched one set of speaker leads on only one channel to compensate for improperly wired speaker cables. The phase switch on the DacMagic Plus changes the positive and negative leads on both channels so the absolute phase is reversed. A signal that would have caused a speaker cone to move outward now will make it move inward.
For audiophiles who want to know exactly what the sampling rate is for every piece of music they play through their computer’s playback chain, the DacMagic Plus includes a set of blue LEDs that inform you of the current rate. Since some players and computers will automatically downsample higher resolution digital streams if not configured properly, these notification LEDs can be especially useful to make sure that your new 192/24 music file is actually being played back at 192/24.
As I mentioned earlier, the DacMagic Plus lacks a remote control. Adding a remote is not even an extra-cost option. If you must have a remote control you are out of luck unless you couple the DacMagic Plus with an amplifier or powered speaker system that includes its own remote.
Some cynics will tell you that the only difference between a $5000 DAC and a $649 DAC is the size and weight of the cabinet and thickness of the faceplate. The Cambridge Audio DacMagic Plus is one of the DACs they will probably champion as a prime illustration of their point. It is a very good DAC, with the kind of performance that will keep many audiophiles content for a good long time.
And which of the three filter settings will guarantee lasting sonic nirvana? After over a month of listening I still have no idea which setting is best. For 320 BPS MP3 files I used the steep filter settings, but with full rez and higher rez music files I vacillated between the linear and minimum phase settings. While I did hear differences between the two, neither proved to be a consistent preference. On some recordings linear phase seemed to have better depth recreation, but on others the minimum phase presented the most cohesive and well-defined soundstage. On my own recordings I could definitely hear the reduction of high-frequency air with the steep filter, but as to which of the other two was a better match, it was a toss-up. Let your ears be your guides.