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Wednesday, November 10, 2010

Personal Audio!
CEntrance DACport USB DAC,
Audiophile Headphone Amp

Price: $399
Likes: audiophile-class sound, small size;
Dislikes: no 192 kHz output.

by John Gatski

Computers are becoming standard fare for serious audio playback and recording. Talk to most ardent audio users, and they are downloading, streaming, ripping, recording, and editing on their desktop or laptop. Without peripherals, however, computer audio quality is mediocre at best — with marginal speakers, internal DACs and headphone amps. You need quality add-ons to really get the best sound out of a computer.
For many audiophiles and pro audio end users, an external DAC makes computer audio come alive. Several audiophile DACs are USB capable, as well as offering connections to optical SPDIF-equipped computers (thank you ,Apple). **However, full-size DAC placement can be a challenge on your crowded desktop. And on the go, an AC-powered DAC/headphone amp takes up room in the brief case and needs that AC umbilical cord. The ideal portable computer DAC should be small, internally powered (or by the computer), and easily connected to a laptop. It should be a product — like the CEntrance DACport.

From the folks who brought you the USB-based AxePort (computer interface for electric guitar) and MicPort (microphone interface), CEtnrance has made the perfect-sized DAC for computers on the go or on the desktop. The diminutive DACport is a 4-inch cylindrical DAC/Class A headphone amp that delivers clean, up-to-24-bit/96 audio, from a USB jack — without any additional drivers.
Priced at $399, the assembled-in-U.S DACport sports a volume control, USB jack, 1/4-inch headphone jack and status light. That’s it. Spec-wise, the DACport boasts a greater than 110 dB signal-to-noise and dynamic range performance. (Check out our lab test measurements).
The DAC chip is supplied from Asahi Kasei Microsystems, and, of course, the CEntrance-developed USB/audio interface (also licensed to Lavry engineering, Benchmark and others) delivers a high-performance, low-jitter signal via the USB port with no external drivers needed.

The DACport quickly becomes a high-quality audio companion for your computer — an indispensable tool for your music to be played back in full fidelity on the road or on the desktop.

The CEntrance DacPort contains a multi-stage power supply that steps up the 5V DC USB bus power to provide enough zip to power headphones in Class A, resulting in exemplary performance for such a small DAC/headphone amp. It quickly becomes a high-quality audio companion for your computer — an indispensable tool for your music to be played back in full fidelity on the road or on the desktop.

I connected the DACport to my Macbook Pro 17-inch laptop and played numerous audio files that I downloaded from high-res sites (HD Tracks, I-Trax) — as well as dubbed-DVD-As and SACDs (DSD to PCM via Benchmark ADC1 A/D). To increase my high-resolution, computer-listening choices, I turned to the Oppo BDP-83SE universal player. Its unencumbered SPDIF digital port allows 24-bit/96 kHz sample rate (or even 192 kHz) DVD-A stereo tracks to be copied to a digital recorder without downsampling.
DVD-A tracks copied for the CEntrance test, included Natalie MerchantTigerlily, Elvis PresleyNumber Ones, Neil YoungHarvest, George BensonBreezin', QueenThe Game, and others. The DVD-As were copied to either a TASCAM DVRA-1000HD high-res HD/DVD recorder or TASCAM HDP2 mid-size portable FLASH recorder. They were then transferred to the computer. I could have copied them straight to my Apple computer, as well, the via the Oppo TOSLlink jack.
I also recorded my own acoustic guitar tracks through a pair of Audix SCX-25 microphones, amplified by the made-in-U.S.A. True Systems discrete P2 mic preamp. The analog signals were recorded to the MacBook Pro using the Benchmark ADC1 A/D converter.
Headphones included AKG K701 and K702s, Shure SRH-840, Grado SR-325s and a couple pairs of Ultrasones. For comparison, I listened through the Benchmark DAC1 Pre DAC, Lavry DA-10 DAC, a Benchmark standalone HP-1 headphone amp, the headphone amp in the MacBook and the headphone amp in the TASCAMs.

Connecting the DACport
To install the DACport, I plugged it in to the MacBook Pro computer via the included USB cable. Since it operates at the USB 1 spec, there are no drivers to install. However, in order to play music from your computer, you must select the DACport as your playback device in the computer’s audio system setup menu, and in the playback program setup menu. Some programs will automatically lock to it, but others need the DACport option manually activated.
Sample rate and word length also must be checked and set in your computer audio system and playback program setups. Since the system and playback program’s sample rate/word length could be different than the music being played, they must be synchronized.
Listening through the AKG K701, I could immediately tell that the CEntrance DACport is a very good DAC/headphone amp. I could hear the air around the cymbals and the voice timber, stereo image detail and plump electric bass were all very similar in sound to my reference DACs.

In the Apple Macbook Pro, the master audio settings are made in the Audio/MIDI utility. So I selected the DACport menu item as the output source, and 24-bit and 96 kHz sample rate as the playback parameters.
Because I used Bias Peak 6.0 as my playback program, (an excellent professional-grade, stereo recorder/editor/processor software that also plays and converts FLAC files, I made sure that its sample rate setting was 96 kHz. Peak always operates in the 24-bit playback mode.
In the Mac, if you do not check and, if necessary, synchronize the sample rate and word length in the system audio and playback program setups, high resolution playback may not occur. Your 24-bit/96 kHz music files could be truncated to 16-bit and the sample rate internally converted to whatever Audi/MIDI setting rate was previously selected. I have had cases with the Mac where a 24-bit recording was truncated to 16-bit and the sample rate converted to 44.1 kHz by the computer because I forgot to check the audio/MIDI master settings. So just make sure you check it every time you play music.

The audition
I plugged the DACport into the MacBook Pro to let it break in for a few hours. Being a Class-A headphone amp, the DACport takes the 5V DC and steps up the voltage to 18v internally, which means the aluminum cylinder gets pretty warm after a half hour or so. After my “break in,” I donned my reference AKG K701 headphones, clicked open Bias Peak and played Natalie Merchant’s mid-1990s single, Carnival. I had digitally dubbed the track from the limited-release 24/96 DVD-A of the album Tigerlily. It is a well-recorded and mixed pop/alternative rock song — with distorted guitars and fairly open air around the drum cymbals. Much better sounding than the CD version.
Listening through the AKG K701, I could immediately tell that the CEntrance DACport is a very good DAC/headphone amp. I could hear the air around the cymbals and the voice timber, stereo image detail and plump electric bass were all very similar in sound to my reference DACs. Versus my standalone headphone amp, I heard no coloration, harshness or noise from the DACport.
I switched music and played the digital dub of George Benson’s Breezin' DVD-A; the DACport again showed its quality quotient. The low-impedance AKGs are not easy to drive, and for many recordings, I turned up the wick past half to hear the music at louder levels on the K701 and K702, but the DACport never complained or ran out of steam. Not only could the phones be played back at higher levels using the DACport, but the stereo imaging, fine transient detail and accurate bass reproduction also held up. The headphone amp is extraordinarily quiet.
The DACport had no problem with different headphones. The Ultrasones exhibited their smooth mid and low treble that I hear on better headphone amps, and the Grado’s SR-325 elevated presence was clearly heard as well. The $200 closed-back, Shure SRH-840 was a perfect match for the DACport, and they became a well-used monitor tandem when recording or editing fresh acoustic guitar tracks.
Computer audio recordists will love the low-fatigue factor when using the DACport for lengthy editing and processing sessions. I recorded and edited 20 acoustic guitar tracks using the DACport, with no complaints or "bleeding" ears.

The DAC and the headphone amp are quite good — even compared to more expensive separates. No AC plugs, no batteries. Just plug it in to the computer, and sit back and listen. I never take my Apple laptop anywhere without it.

I have no major criticism of the DACport. The tracking was a little off at low levels (a little bit more output in the left channel), but at the normal gain, it was identical output on both channels. Also, since the DACport is just a few ounces and round in its shape, it can roll freely on your desktop with just a slight tug on the cable. It needs to be secured with the included cable tie that comes with it. On my desktop, I made an enhanced tie and mounted it to the bottom of my external LCD. With a laptop, it could be fastened to your belt.
Also, It would be nice if the DACport could decode 192 kHz PCM files, but it does not. Maybe in the future? I know that the M-2 Tech Hi-Face interface can output 192 kHz audio from USB-2, so maybe future versions will get such an upgrade.

The verdict
The CEntrance DACport is a versatile, portable, high-resolution playback tool for all computer audio niches: casual listening, audiophile playback and professional engineer/musicians who record, process and edit on the computer. The DAC and the headphone amp are quite good — even compared to more expensive separates. No AC plugs, no batteries. Just plug it in to the computer, and sit back and listen. I never take my Apple laptop anywhere without it. A Stellar Sound Award for the DACport.

Second Opinion!

CEntrance DACport

The CEntrance DACport 1 is the right way to get high quality audio from a computer without all of the inherent clocking and jitter contamination. Computers are notorious for creating jitter in a digital data stream do to all of the simultaneous tasks that a computer is asked to do. CEntrance has addressed this problem by using a 24/96 USB controller chip to feed their proprietary dual stage JitterGuard™ clock management system resulting in 10ppm of low-jitter precision. With that kind of jitter performance from a 24-bit DAC and an all Class-A analog output stage, the listener gets a level of performance found only in the highest-end equipment.

Whether driving my Joe Grado hot-rodded HP-1’s or the new Shure SRH-840 headphones the sound is smooth, full and lush — with all of the detail you would expect from a truly high-end audio component.

—Tom Jung

EAN Bench Test!

Centrance DACport/

USB Headphone DAC

by Bascom King

The CEntrance DACport is a nifty little device that connects to a USB port on one’s computer and drives headphones with a class A driver circuit that delivers surprisingly good sound.

Measurements were made on my lab computer that controls my AP (Audio Precision SYS-2722) measuring instrument. Various .wav files were generated and played back via the Foobar 2000 program that runs on the lab computer. The output of the DACport was run into the analyzer input of the AP for measurement.

Dynamic range was first looked at for full-scale 1 kHz test signals at 16/44 and 24/96 resolution. As is not uncommon, the two channels measured a bit differently at the higher resolutions. Results were for Lch & R-ch for the 16/44 tests, -95.7, -95.3 dBFS, and for the 24/96 tests, -114.0, -104.2 dBFS.

Next, THD was checked for a full scale 0 dBFS 1 kHz test signal run as a 16/44 .wav file both for a high impedance load (like if it was used as a DAC to drive one’s sound system) and for a 50 ohm load. The measurements are in a 22 kHz bandwidth. The unit’s volume control was fully up.

For Lch/Rch, results for the high impedance load were: 0.0028/0.0034%. For a 24/96 .wav file, results were 0.0019/0.0032%. For the 50-ohm load, results were 0.02/0.022%. See Figure 1 for a plot of how 1 kHz THD+N reduces with input level with the 50 ohm load with 24/96 data. With the volume control was set for 6 dB lower output, the full-scale input level distortion reduced to about 0.01%.

Attainable output power into the 50-ohm load was 185 mW. With an 8-ohm load, the full-scale input signal was clipping the output with the volume control fully open. With the volume control reduced to the VOC (visual onset of clipping, about 0.5% THD), the output power was about 110 mW.

Frequency response was quite flat from 20 – 20 kHz at the 44.1 kHz sample rate. For the 96.0 kHz sample rate, a plotted response is shown in Figure 2 and has an approximate -3 dB down bandwidth of about 45 kHz.

A couple of miscellaneous observations on the DACport: The overall digital input/analog output signal polarity for the DACport was non-inverting. Output impedance was about 11 ohms. All in all, very good measured performance from a small DAC/headphone amp.

Bascom King is owner and chief technician for BHK Labs in Satna Barbara, Ca.

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