CEntrance DACport USB 96/24 Headphone Amp
Published on June 26, 2010
CEntrance DACport USB 96/24 Headphone Amp
Class A amp, adaptive isochronous USB input
USB 1.1 or 2.0 compliant
Works with Mac, PC or Linux OS
No driver software
Output: ¼” stereo phone jack
(¼”-to-1/8” stereo adapter provided)
Sample rates: 44.1, 48, 88.1, 96K
Word lengths: 16 or 24 bits
JitterGuard clock management system
Freq. response at 96K: 20Hz-40kHz
Max. output power: 1.5V
With belt clip, 6’ USB cable, felt carry pouch
Size: 4.5” length x 1” diameter
Weight: 2.4 oz.
8817 Mango Ave.
Morton Grove, IL 60053
With the huge popularity of mobile digital audio devices and computers, the use of headphones for listening is probably becoming as widespread as during the earliest days of radio, when nearly everyone listened via headphones. Headphones have developed radically since that time, and so have dedicated amplifiers for achieving the best possible sonic quality from them. There is a sizable community of headphone fans today who have moved way beyond those poor-quality, hearing-damaging white ear buds supplied with iPods. Many of them congregate at the web site www.Head-Fi.org
The first dedicated headphone amps for mobile use were pretty heavy and bulky. Simpler and lighter ones came out, such as the Boosteroo, but they just amplified the signal with no audiophile pretensions to improving it. HeadRoom and others came out with portable headphone amps that did a better job of offering an improved signal on headphones. Most of them sourced only an analog stereo signal, but recently more USB models have been introduced which operate with computers and mobile digital gear. CEntrance, which develops and licenses different audio and entertainment products, and works with such industry leaders as Benchmark, Alesis and Zoom, has now launched their DACport USB Amp, which is designed to be one of the most compact hi-end headphone amps yet – with Class A architecture – not requiring any other power supply than the USB connection, and totally cross-platform with any computer operating system.
Having no batteries makes the DACport a much more compact unit, and not having to deal with any driver software makes it very convenient to use. I was unable to use my best headphones with the DACport because they are the AKG K-1000s which require much higher voltage, so I used my Grado SR-80s, which though at the lower end of the Grado line I find very close sonically to the previously flagship Grado phones, which I sold some time ago.
You can also use the DACport as a high-quality D-A processor between your computer, an iPod or a USB hard drive, and feeding your home audio system via a cable with stereo RCA plugs at one end and a ¼” stereo phone plug at the other. In that application, it is suggested you turn the DACport level control to maximum and then use your amplifier/preamp/receiver to adjust the volume. There is no danger of the DACport overloading from this.
A great deal of thought obviously went into this fat-cigar-shaped little headphone amp. There are over 200 parts crammed into the silver and black case, which does heat up a bit in use due to the Class A circuitry. An audiophile-grade D-A converter plays most of the current sampling rates (except 192K) – 96K, 88.2K, 48K, standard CD’s 44.1K and MP3 files. As well as either 16-bit or 24-bit word length. It does not upsample or resample, but plays back each audio file at its native rate. However, it has such advanced processing that even data-reduced MP3 files take on a new clarity, with less obvious compression effects. Its AdaptiWave High Resolution USB technology offers true 96K/24bit audio quality from 96/24 files.
By the way, John Siau, CEO of Benchmark, has said that most A-D and D-A converter chips perform better at 96K than at 192K, and that he believes 96K/24 is more than sufficient for the best fidelity. He says the differences between the two may not be audible, but 96K will usually measure better than 192K. Evidently CEntrance feels the same, and I must say I agree.
There is no on/off button on the DACport. Instead, the moment you plug in a USB cable connected to a computer or other digital device, the little On LED lights up. The only control on it is a small analog volume knob. When you plug in the USB cable, the DACport takes over as the main sound card in your digital component. This is automatically a big improvement over almost any computer’s built-in sound card. It removes the card from all the close-by radiating components inside any computer. Plus some PCs downgrade all 24-bit files to play as 16-bit, and this resampling and any artifacts it causes are thus bypassed.
The DACport is direct-coupled and capacitor free, to ensure audiophile quality all the way up to the phones. The low-distortion Class A amp runs on +-9V bipolar supply, which equals 18V rails for plenty of headroom and power to drive any headphones with standard ¼” plugs.
Much attention has been focused on the elimination of jitter in the DACport. This problem has received varying degrees of attention since it came under the spotlight some years ago. It is the time variation of a periodic signal and has become an important concern in digital audio. On an audio sampling clock jitter can cause non-harmonic, non-musical distortion, which is much more audible than harmonic distortion. I was amazed to read that jitter is part of the USB, FireWire and Ethernet cable interface in order to reduce radio interference. This relatively high level of jitter must be attenuated by the converters.
(Speaking of FireWire, why are all these new digital audio products designed for USB rather than FireWire, which can handle more data transfer and is much faster? Even with the latest versions: USB 2.0 and FireWire 800. I may not understand all the technical points, but the emphasis on USB sounds to me like the old VHS vs. BetaMax format war – in which Beta provided better picture and sound but still lost out.)
Anyway, there are two technologies for the clock management system, which hopes to eliminate jitter. The widely-used on is isochronous adaptive mode, in which the host computer controls the data flow. This is used by both the DACport and the Benchmark D-A processors. Another approach is asynchronous mode, in which the DAC itself has the system clock and controls the data flow. This is used by DCS, Ayre Acoustics and Wavelength. There are pros and cons to each method.
The DACport uses a military spec clock oscillator with 10ppm precision in their proprietary JitterGuard clock management system, which they have also licensed to Benchmark, who have their UltraLock clock system. John Siau says that audible jitter artifacts are usually heard in the midrange frequencies, which get muddy and lack clarity. The clock systems both use are claimed to be immune from any jitter, thus improving the clarity of digital audio at all the different sampling rates.
The other headphone outs which I had around were first of all my AKG headphone amp – designed especially for the high output required for the K-1000 headphones, the headphone jacks in both my Sunfire AV preamp and my new iMac, my Benchmark DAC1 headphone amp connected to my main audio system, a Boosteroo multi-headphone battery amp, and Headroom’s battery-powered Total BitHead portable. My sources were MP3 files in my iTunes on the iMac, standard CDs played on the iMac, some xrcd and K2HD CDs, 88.2 FLAC audio files of an M*A piano album, and several 96K/24bit classical DVD-Rs from the HDTT label. (I should reveal that I don’t own an iPod, iPad or iPhone and don’t intend to.)
I should also reveal that for me nothing equals the fidelity of the now-discontinued K-1000 phones with their large dedicated amp, although I haven’t sampled any of the latest ultimate headphones from makers such as Grado, Stax and Ultrasone. I think we can also drop the built-in Sunfire headphone amp and the Boosteroo from the equation. (In fact the latter had terrible distortion, and forget Dolby Headphone on the Sunfire, which sounds awful.) The HeadRoom – which is either analog or USB input – provided some enhancement from my portable CD player, but nothing noticeable when being fed the analog signal from the new iMac in comparison to simply plugging my Grados directly into the iMac. (I don’t recall the headphone output was such good quality on my previous iMac.) However, when using the USB input on the BitHead – same as the DACport – there was a definite increase in clarity and detail, but not to the level of the DACport. The DACport had a cleaner and more focused overall quality. This was on the Scherzo from the Shostakovich Piano Quintet in G minor with the St. Petersburg Quartet. Violin tone can easily sound steely and raspy with poor amps, and there was no hint of that with the DACport.
With MP3 files of all sorts the DACport provided an improved fidelity over plugging directly into my iMac. There was more detail, a richer and fuller sonic, and greater overall clarity. I enjoyed running thru my sizeable library of tracks in iTunes (which are all AIFF files), which I realize now I have been collecting for years – ever since I stopped making what I called “Cassamplers” – 90-minute cassettes of tracks on various discs which I wanted to highlight and save. I stopped doing that with No. 168 in 2000, but they all still play fine and I have a combo cassette/CD player in my car – with Circle Surround yet. My thousands of cassettes and CDs are the reasons I’ll never want an iPod.
I had a DVD-ROM from M•A Recordings of the Mathias Landaeus Trio’s album Opening, with both 88.2K/24bit FLAC and 176.4K WAV files. I converted the FLAC files using the app Max, and compared the original 44.1K CD with the 88.2K files. Clearly, just as with 96K/24 audio files, the 88.2 files had greater clarity, detail and depth, with no hint of digititus. Using the direct output of my iMac for the CD source vs. the DACport for the 88.2 processing, the enhancement of the latter was even greater.
Turning to the highest-res audio files I had on hand, short of the 192K files, I tried several of the 96K/24bit DVD-Rs produced by High Definition Tape Transfers (HDTT). Although I immediately heard the greater detail and resolution of the 96K files vs. the standard CD sources I had been auditioning, I was surprised by the rather dated-sounding sonics of this particular recording, which came from a 1960 London 4-track prerecorded tape. (Bruckner’s Fifth Symphony, with Hans Knappertsbuch conducting the Vienna Philharmonic Orchestra.) I didn’t recall noticing that when playing back on my main system using the Benchmark DAC1 and speakers. I moved it to the other room, played the DVD-R on my Oppo player and plugged my Grado phones into the DAC1. Yes, this was clearly not a modern recording, but now there was an additional heft and impact to Bruckner’s symphony that I wasn’t hearing via the somewhat lighter sonics of the DACport. Perhaps the heftier power supply of the DAC1 was a factor here, vs. the DACport drawing all its power off the USB cable from the iMac. (Of course the DACport is about ⅓ the price as well.)
I turned next to HDTT 96K DVD with the wordy title “The National Orchestra of Spain – Rafael Fruhbeck de Burgos.” Also from a London 4-track tape, this one is of a less dated sonic and the Spanish melodies sound terrific via either the DACport or DAC1. I also got out the F.I.M. xrcd24 of the same conductor doing the Suite Espanola of Albeniz with the New Philharmonia. Both masters would date from London/Decca of the 1960s and sound equally rich and exciting, though with slightly different timbre. Perhaps a bit more high-frequency clarity on the DVD-R transfer, even though it just came from a commercial pre-recorded 4-track tape.
The DACport sounded far better than any of the portable headphone amps. It think it is understandable considering the vast difference in price and the heftier power supply of the Benchmark DAC1, that that would sound somewhat better, with greater bass support. However, all in all, I believe DACport has achieved an enviable super-compact and portable Class A headphone amp that should find wide usage for those into mobile digital audio.
- John Sunier