Equipment Review No. 1   September 2001
red line

Onkyo USB Digital Audio Processor for computers

Connects to Universal Serial Bus ver. 1.1 of PC or Mac

Analog or digital inputs

Digital input rates: 32, 44.1, 48 KHz

Digital output rate: 44.1

S/N Ratio: 100 dB

Output level: 1.0 Vrms

Power supply: uses USB power supply, but optional 7.5v AC adapter available

Size: 1 15/15" x 8 1/2" x 6 9/16"

Weight: 1.5 lbs.

SRP: $249.95



Some years ago I bought a Macintosh with "AV" added to its number designation, intended for audio and video recording and editing. I had assumed being entirely a digital computer that it would have digital inputs and outputs for audio - so that I could, for example, feed my DAT tapes in and edit them in the digital domain. Not so, I soon learned. Only analog I/Os, meaning all digital signals had to go thru extra steps of processing: Digital-to-Analog, then Analog-to-Digital and finally Digital-to-Analog yet again. Each step meant further degradation of the original signal, however subtle.

Now things are different and both PCs and Macs have digital I/Os, plus we also have USB and FireWire for more advanced connecting options. However, one can't expect the highest quality out of a D-A built into a small home computer, especially one as tiny as my new iBook laptop. Also, there are the electronically noisy crowded innards of any computer that can't possibly provide the best environment for clean digital sound processing and delivery. It's surprising they sound as good as they do. What we have at hand is a better alternative to the Mac and PC internal sound cards. This little processor moves the D-A, connecting and control functions outside of the computer via the single USB connection which handles both the power supply and the digital signal output. (There is also an accessory wall wart available for situations away from the computer or where an older computer lacks the current necessary for operation of the unit.)



The SE-U55 is first set for either Windows or Mac operation with a small slide switch on the bottom. Then the USB cable is connected, and if you're using only headphones, that's about it. Plug your phones in the front jack and you're in business. There is also a mic jack. There are both line in and line out analog jacks, so you would input an outboard audio system from the outputs or go directly to a pair of powered speakers. If you want to feed any analog signal into the processor you would use the analog inputs. The small unit boasts two more pairs of jacks: digital coaxial in and out plus digital optical in and out. A typical CD, MD or DAT player would go into one of these inputs and recording would be done from the outputs. The SE-U55 also is supplied with two PC-only music software applications: FUSE and CarryOn Music - Mac owners will usually already have their own software - likely either Sound Jam or iTunes.

Speaking of software, the above really wasn't entirely it after all. You must set up your Mac to recognize the SE-U55 using the Apple System Profiler. You also need to access the Sound control panel and select USB as both the input and output and then quit and restart your audio player software before you'll get sound. You may also need to make some changes to your audio player software as well.



To record from an analog source with the SE-U55 (using a Mac), you go into the analog line in or use the mic input. The function selector is turned to either line or mic as appropriate. In the Sound application on the Mac you select the sampling rate you want - probably 44.1 16 bit and stereo for most purposes. You then bring up the recording screen, adjust the input level on the SE-U55 to get a good reading on the software meter display, and then click on Record. Recording from digital sources is similar except that you then patch to either the coax or optical digital inputs and set the selector on the SE-U55 for Internal.



I compared a number of different digital sources three ways, using my Grado headphones into either the analog audio jack on my iBook or the headphone jack on the SE-U55. The two options at the U55 were either feeding it an analog signal from the same audio jack of the Mac used with the headphones, or using the digital feed via the USB cable (after selecting USB on both input and output in the Mac Sound panel and quitting and restarting iTunes). I also used the analog outs on the Onkyo unit to feed the auxiliary IN of my JVC mini stereo system with its speakers on either side of my monitor. (It would have been silly to make any comparisons with the half-inch-wide stereo speakers in the iBook.)

First up was a new Dorian CD, Madrid 1752. The vocal soloists had a fussy and edgy sound with only the iBook electronics and headphones. The instrumental ensemble seemed distant and out of focus. Switching to analog in and out on the U55 improved the sonics somewhat, even using it just as a sort of booster amp on the way to the Aux input of the JVC system. The U55 may have a superior headphone op amp to that in the iBook. The last step involved disconnecting from the analog out on the iBook and using the USB cable to not only provide the power but also the digital out from the computer to the U55. Now the instrumental ensemble came into improved focus and the vocalists lost their edgy quality almost completely. Similar improvements were heard using the new JVC xrcd2 release of Beethoven's Seventh Symphony conducted by Fritz Reiner. The wonderful sonics of this early stereo masterpiece came thru with much greater transparency and impact using the digital I/O - with both the headphones and the small speakers.

A recent Sony Classical reissue of more Glenn Gould Bach piano performances sounded alright directly on the iBook with the Grados. Gould was singing as usual and I realized his recordings are the last thing anyone should be listening to on headphones, but the extraneous sounds were still primarily in the background. With digital processing in the U55 however, one could hear not only the singing with greatly improved clarity but also a sound like ticking on one track and Gould actually talking to himself sotto voce on another track! Also, the sonic differences from one track to another (recorded at different times and venues) now stood out strongly whereas they were minimized before. The exciting live duo performance in Montreal by bassist Charlie Haden and pianist/guitarist Egberto Gismonti (ECM) was already enjoyable strictly on the iBook with phones, but switching to the external digital processor and speakers provided an almost surround sound experience in putting one right in the concert hall - in spite of the lack of low frequency support for Haden's bass. That, by the way, was a disappointment in the unit - seeing that it had no subwoofer out jack, since most computer speaker systems now include at least a semblance of a sub.

I find I seldom listen to the online audio streaming from stations because the quality seems so poor on most of them, even with a broadband cable connection and a 500 MHz Mac. The iBook with iTunes makes it easier to access some of the huge supply of online streaming available. I tried some electronica, which was streamed at only 40 kpbs and sounded muffled and constantly varying in high frequency content in the two channels something like an old open reel tape that was pulling away from the tape deck's playback heads. Switching to digital in and out on the U55 cleaned up the music amazingly and while inconsistencies could still be heard clearly on the headphones, it sounded great via the speakers.

Next sampled was a channel playing film soundtrack material at 56 kpbs, called Cinemascope Radio. The music was a sort of piano concerto and quite muffled and uneven at the analog out of the iBook. After digital processing in the U55 it cleared up beautifully and sounded quite close to actual CD quality. The few netcasters offering 128 or 160 sampling rate sounded even better of course. It made me think perhaps there is hope for MP3 after all (and surely for the greatly improved MP4 codec which is next up). In a way it's not unlike the situation of the first CD players sounding so bad with their cheap and cheerful analog circuitry, and the first outboard D-A processors offering a substantial improvement in their sonics.



The U55 would be a very sensible upgrade to the audio quality of any computer - not just for playback but for improved quality in stored MP3 files and in burning CDs. I've long had a very lengthy interconnect cable running from my Mac to an input on my main audio system's preamp. One could go directly from the digital out of a computer to an outboard D-A at your main audio system, but that would require a super-expensive lengthy digital cable which may not even exist. Using the U55 near the computer means you have more of a boost on its analog out to send an improved signal with less loss to your preamp or receiver.

- John Sunier

Back to top of this page

To Next Equipment Review

To Index of Equipment Reviews for this month

Return to SEPT 01 Home Page