CEntrance DACport USB headphone amplifier Page 2

I picked up the review sample of the DACport at the 2010 CES, which is also where electric bassist Dean Peer gave me a copy of his new album, Airborne, available as 24/96 WAV files on a USB drive (Cardas Audio). I got to know the album through the DACport—remembering, of course, to exit iTunes, reset the default sample rate to 96kHz with the Mac's AudioMidi setup utility, then restart iTunes. "N'est-ce pas" is currently my favorite track from Airborne, with its melodic arpeggios, picked out on artificial harmonics, contrasted against a simple bass line and off-beat snare-drum rimshots. This recording's startling transients were reproduced without compression or softening, and, even on headphones, where so much of the imaging takes place inside one's head, there was an impressive sense of space. This was especially true with the CEntrance DACport driving the Sony headphones rather than the more laid-back Sennheiser cans.

How do I know it's true?
I compared the DACport with my long-term reference headphone amplifier, the Benchmark DAC1 (non-USB model, $995), which I'd purchased after John Marks' enthusiastic encomium in July 2003. I drove the Benchmark from the TosLink S/PDIF output of my MacBook laptop, matching levels to within 0.1dB with a 500Hz test tone. The CEntrance sounded as clean and transparent in the highs as the Benchmark on "Many Chinas," from Marc Isham's classic 1986 album Vapor Drawings (ALC, originally CD, Windham Hill), but lacked a little LF slam on the synth playing the bass line and the sampled drum sounds. However, the slightly shut-in sound of the accompanying piano on Giora Schmidt's performance of the Franck Violin Sonata, from his 2007 album Vocalise (MP3 download, Endeavour Classics), benefited from the DACport's lighter-balanced low frequencies, and the violin sounded a little airier. And on Elvis Costello's "Shipbuilding," changing to the Sony MDR-7506es gave high frequencies that were too "spitchy" and sibilant through the Benchmark compared with the HD-650s; by contrast, the CEntrance kept the recording's treble under better control.

On the other side of the coin, the low frequencies on Annie Lennox's "Downtown Lights" had better separation from the sampled kick-drum sound and deeper subjective extension with the Benchmark, so that the octave drops in the bass line were better resolved. And paradoxically, even after I'd checked and rechecked the level matching to make sure it was still okay, the DAC1 sounded a little louder than the DACport with both the Sennheiser and Sony headphones (which is why it is fruitless to try to match components by ear). Ultimately, when it comes to subjective bass extension and authority, there's no substitute for a beefy power supply, which the Benchmark has, while the CEntrance has to rely on what the host computer can supply it. Even so, the DACport proved a worthy, if less versatile competitor for the Benchmark, at 40% of its price.

The words I have to say
May well be simple but they're true

In mid-March, I heard of the death of Scottish singer-songwriter Lesley Duncan, at 66. I met Lesley only once—she married Tony Cox, the producer of two albums I played bass guitar on in the mid-1970s—but she was a delightful lady taken too early. Neither Amazon nor iTunes has available "Love Song," the 1969 hit that established her in the UK, but I downloaded from iTunes the 256kbps AAC file of the version Elton John recorded for his album Tumbleweed Connection, on which Duncan duets with him and provides backing on acoustic guitar.

Listening to this version of "Love Song" as I write the conclusion to this review, with the CEntrance DACport driving the Sennheiser HD-650s, the delicate interplay of the voices in the first refrain, where Elton first doubles his line in unison, then Lesley adds a double-tracked line beneath his, then another higher in pitch, was laid bare by the DACport but with no artificial spotlighting of detail. The faint repeat echo in the right-channel click track was also easily audible. The blend of Elton's and Lesley's voices sounded deliciously natural and grain-free, though their hard left/right panning in the mix takes a bit of getting used to on headphones. (The center of the soundstage is perversely reserved for the sounds of children playing toward the song's end.)

This song has no bass energy, so neither the difference in low-frequency behavior between the Sony and Sennheiser headphones driven by the CEntrance, nor that between the DACport and Benchmark amplifiers, was relevant. However, as the Sony's lows continued to be better defined than the Sennheisers throughout my auditioning, I did investigate whether the difference was simply due to the interaction between the DACport's 10 ohm output impedance and the impedance of each headphone. The Sony's impedance at 1kHz is 74 ohms, the Sennheiser's is 320 ohms at the same frequency. Both feature a broad rise in impedance in the midbass, centered on 70Hz, where the Sony reaches a maximum impedance of 95 ohms, the Sennheiser 475 ohms. Driven by the CEntrance, the Sony's response will peak by 1.6dB at 70Hz compared with the level at 1kHz; the Sennheiser will peak by 3.4dB at the same frequency.

While the 1.8dB difference in the midbass boost will be audible, I don't think it entirely explains the different in low-frequency quality I heard between the two headphones driven by the DACport. On the other hand, as the DAC1's output impedance is less than 0.5 ohm, there will be no modification of either pair of headphones' frequency response. The Sennheiser's low-frequency output will be boosted by up to 3.4dB when driven by the CEntrance compared with the Benchmark, which does correlate with what I heard in my auditioning.

The Downtown Lights
Given my prior suspicions about the sonic effectiveness of operating a USB audio interface in adaptive isochronous mode, I was pleasantly surprised by the sound of the CEntrance DACport, especially with 24/96 files (footnote 2). Its clean, grain-free presentation with airy high frequencies provided me with hours of fatigue-free headphone listening. Its bass was better-defined with the Sony MDR-7506 headphones, but that's not to say that I didn't also appreciate the DACport's performance with the smoother-sounding Sennheiser HD-650s. I wholeheartedly recommend CEntrance's DACport: a great-sounding product at a great price!

Footnote 2: CEntrance suggests using the DACport as a line-level DAC/preamp with a ¼"-RCA adapter cable. I didn't have time to try this during the preparation of this review, but I will pass the DACport on to one of my colleagues to investigate this use.
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