- Written by John E. Johnson, Jr.
- Published on 11 June 2009
Cambridge Audio has long been known to produce very affordable products that include CD players, DVD players, Receivers, Amplifiers, and Speakers.
Recently, they added something very special. A DAC that has high specified performance, including being fully differential, at an unheard of price of $479. Everywhere I have read about this product, people are raving about it.
So, I decided to get one myself, and not only listen to it, but perform bench tests, which no other review has done. I have a Squeezebox Duet, which is a wireless music streamer that plays music from my media server downstairs. The DAC inside the receiver is pretty good, but I wanted to see if substituting a different DAC - connected to the digital output of the Squeezebox - could improve things. The Squeezebox Duet costs about the same price at $399, so the DacMagic seemed the perfect choice.
- Design: Differential Digital-to-Analog Converter (DAC)
- D/A Converters: Wolfson WM8740
- Inputs: Two Sets of Coaxial and Toslink, USB
- Outputs: XLR and RCA Analog, Coaxial and Toslink Digital
- Output Level: 4.2 Volts XLR, 2.1 Volts RCA
- Digital Input Sampling Frequencies Supported: Up to 96 kHz; 24 Bit
- MFR: 20 Hz - 20 kHz ± 0.1 dB
- THD+N: 0.001% at 1 kHz
- Power Supply: 12 Volt Wall Wart
- Dimensions: 2" H x 8.6" W x 7.6" D
- Weight: 2.6 Pounds
- MSRP: $479 USA (Available from Audio Advisor for $429)
- Cambridge Audio
Most hi-fi components are designed at rack width, about 17", so they will stack or fit into an equipment rack. If you look inside some of these components, there is a PC board in one corner and a lot of wasted space.
The DacMagic is designed as an accessory that can be placed anywhere because it is relatively small. I placed the review unit on top of my CD player and the Squeezebox receiver on top of the DacMagic.
To the left is the power on/off push button, an input selector button, and a filter/phase button which selects the filters. You can select three filters: Lin (Linear), Min (Minimum), and Steep. Linear phase has low ripple and is time coherent, but its impulse response has some pre-ringing. Minimum phase has lower ripple than Linear, and no pre-ringing, but some time coherency is lost. The Steep phase has a very steep attenuation just outside the pass band, so it blocks aliasing at 22 kHz by 80 dB, but it does have pre- and post-ringing. So, in other words, you have choices, each with its advantages and disadvantages. Most outboard DACs don't have these choices. You can also invert the absolute phase by pressing the Filter/Phase button for two seconds. When the Phase LED lights up, the phase is inverted.
Dual stereo Wolfson DAC chips are used, resulting in a fully differential (balanced) circuit. This reduces noise and distortion.
The unit will accept digital signals up to 96 kHz, 24 bit. The input sampling frequency is displayed on six small LEDs at the right hand side of the front panel. They indicate 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, and 96 kHz.
The rear panel has plenty of connections: there are two digial inputs that have the choice of RCA or Toslink, a USB input, and a set of XLR balanced and RCA unbalanced outputs.
I played music from my media server downstairs to the Squeezebox Duet, and the Toslink digital output of the Squeezebox to the Toslink digital input 1 on the DacMagic. I used the XLR outputs from the DacMagic connected to a BAT VK-5i preamplifier, then to a BAT VK-75SE power amplifier. Speakers were Magneplanar and cables were Nordost.
Immediately I noticed - in comparison to the Squeezebox's DAC - an improved clarity in the detail. Instruments were more delineated, and therefore, more easily identifiable in their soundstage location.
Leading edge transients, such as the pluck of a lute or classical guitar, were cleaner as well. Midrange congestion, which was not bad on the Squeezebox, was reduced using the DacMagic.
I did not notice any change in the overall response either at the low end (deep bass) or high end (violins playing in upper registers).
I could not really tell any difference between the three filter choices. They all sounded great to me.
On the Bench
In the 1 kHz and IMD tests, a 24 kHz bandwidth was used. For 10 kHz, bandwidth was 96 kHz. Test signals were recorded at - 5 dB. I used one of the DacMagic's XLR outputs connected to the analyzer. The DacMagic outputs quite a bit of voltage, and when the Squeezebox was turned up to full ouput, I only had the lower 20% of the BAT volume control to work with, because any higher than that was too loud for me. So, I set the Squeezebox volume control at about 75%, which I suspect most consumers might want to use as well because it gives you more room in the preamplifier volume control.
At 1 kHz, THD+N was 0.003%.
At 10 kHz, distortion rose to 0.006%. There are three 10 kHz graphs shown below. The first one was taken in the Linear mode, the second in Min mode, and the third in Steep mode. There are subtle differences above the audible band, but the overall distortion was about the same for all three filters. The hump at 80 kHz is the quantization noise that results from using Delta-Sigma (1 bit) DAC chips. The bits are modulated such that the noise is pushed far out of the audible band. As a side note, SACD is also a 1 bit decoding process, so it also has a hump outside the audible band.
IMD was 0.0025%.
The measured frequency response of the DacMagic was 20 Hz - 20 kHz, - 0.3 dB at 20 Hz and at 20 kHz. For the Squeezebox, the frequency response was 20 Hz – 20 kHz, - 0.7 dB at 20 Hz, and – 0.5 dB at 20 kHz.
So, now let's compare the DacMagic to the Squeezebox. I connected one of the RCA analog outputs from the Squeezebox to the analyzer. The volume control on the Squeezebox was left at 75%.
At 1 kHz, distortion was 0.02%, more than an order of magnitude higher than with the DacMagic.
At 10 kHz, THD+N was 0.05%, again, much higher than with the DacMagic.
IMD was about twice what it was with the DacMagic.
I also measured the Squeezebox at just under 100% output to see if distortion improved.
At 1 kHz, THD+N was 0.007%, improved from the 75% output, but still twice what it was with the DacMagic at 75% output.
At 10 kHz, distortion was a still a full order of magnitude larger than the DacMagic, in fact, a bit more than it was at 75% output.
Squeezebox IMD at full output was just a bit less than it was at 75% output, but still more than the DacMagic.
Cambridge Audio has hit a home run with the DacMagic. At $479, it is a perfect upgrade for DACs in music streamers such as the Squeezebox, but it also is some stiff competition for various high end DACs in the market that are used with the digital output from CD transports. It has been rated very highly in several magazines, and Secrets certainly gives it a thumbs up as well.