Reviews of Attainable Hi-Fi & Home-Theater Equipment

Reviews of Attainable Hi-Fi & Home-Theater Equipment

Wavelength ProtonGreat BuyWavelength Audio and its founder-owner, J. Gordon Rankin, are known to high-end-audio enthusiasts for their highly regarded tubed preamplifiers and power amplifiers. It may be a surprise that a company dedicated to the optimization of tubed gear would be makers of USB DACs at all, and even more of a surprise that Rankin has become one of the go-to guys for accurate information about setting up and using USB DACs with computers.

Rankin developed Streamlength, an asynchronous USB software that quickly earned considerable respect within the high end. In asynchronous data transfer, the DAC controls the timing of the data sent by a computer, which in theory should reduce timing errors, aka digital jitter. Streamlength is used in Ayre Acoustics’ acclaimed QB-9 and a few other USB DACs, as well as in Wavelength’s own Proton and other DAC models. If you like tubes and USB DACs, Wavelength may have just what you’re looking for -- each of their three more expensive DACs has a tubed analog output stage.

Some USB DACs don’t specify whether or not they use asynchronous data transfer, but it’s a good bet that such DACs are not asynchronous. Asynchronous data control isn’t the only property of a USB DAC that influences sound quality, but Rankin is convinced that you can’t get top-flight sound from a USB DAC without it. He believes that, as USB playback technology continues to develop, all the best USB DACs will be asynchronous.


The Proton USB DAC ($900 USD) is minimalist: It decodes only USB digital audio signals, then converts them to high-quality analog versions for line-level and headphone output. It measures just 4"W x 2.5"H x 5"D and weighs only three pounds. Its case of extruded satin-silver aluminum is trimmed in black, with the oval Wavelength logo in black on the front.

The Proton’s exterior has no controls, and all connections and status LEDs are on the rear panel: a USB input, stereo RCA analog outputs, a mini-jack headphone output, and one red LED for each sample frequency. There’s not even an AC power supply or power cord. It supports bit depths of 16 and 24, and sample rates of 44.1, 48, 88.2, and 96kHz. In keeping with the minimalist theme, the Proton does not upsample, or interpolate 16-bit sources to 24-bit.

The Proton runs on a rechargeable lithium-ion battery in the shape of a coin. The battery should last three years or a little more, and cost around $10 for the owner to replace. Wavelength says that a full charge will operate the Proton for about 30 hours, regardless of whether the analog line-level or headphone output is used. Unlike many battery types, lithium-ions don’t like being completely drained -- the Proton should be recharged after each listening session. Power to recharge the battery is taken from your computer’s USB port, but unless the battery is almost completely drained, the battery is not recharged while music is being played. (Wavelength says you can expect to hear a slight thinning of the sound if the charging circuit is active during listening.) If the battery starts to charge while music is playing, two of the Proton’s LEDs will light up: either 44.1 and 88.2kHz, or 48 and 96kHz.

When the battery is recharged will depend on how the computer manages power to its USB ports. Current Apple computers will recharge the battery when the computer is in sleep mode. If the Mac is shut down completely, no power is supplied to the USB ports, so the battery won’t be charged. There is more variation among PCs. Most will charge the battery in sleep mode, and some desktop PCs will even recharge it when entirely shut down. Check with your PC’s manufacturer to see how your model handles this.

It’s becoming an accepted fact that you get the best USB sound if you dedicate a computer to do nothing but play music. The debate of Apple/Mac/OS X vs. computers running some version of Microsoft Windows is beyond the scope of this review, but I’ll say this: I began playing music using a Toshiba laptop running Windows 7 and J. River Media Center 15 software. It sounded great to me, essentially equal to the $4000 combination of digital components I use to play discs.

When I heard my very familiar recordings played through a Mac running OS X and feeding the Proton through my own system, I was shocked. I’d heard that "Macs sound better," but I’m always skeptical until I can check something out for myself. Fed by the Mac/OS X setup, the Proton was a whole different deal. Within a month I had acquired a Mac Mini and replaced its spinning hard drive with a solid-state drive, its stock 2GB of RAM with 8GB, and installed Amarra and Decibel playback software.

No letters, please -- I have no idea why the Wavelength sounded better with the Mac rig. I don’t even know if the Mac gear I’m using is the very best to use with the Proton. Some feel that a stripped-down Linux platform might be even better than a Mac, but I’ve never heard or used a Linux setup in my system. Since the Mac Mini playback chain produced better sound from the Proton, that’s what I used for my listening. If you use the Proton with a computer running a version of Windows, you may not be able to get the results described in this review -- then again, you might.

Playback software, too, must be carefully selected. J. River’s Media Center 16, when WASAPI Event Style is used to communicate with the USB DAC, is generally accepted as the best you can currently get for Windows 7. For Mac OS X, the software most often cited as the best available are Amarra, Decibel, and Pure Music. The playback of music by computers and/or USB DACs is still very much an emerging technology, so expect the answer to the question "What works best?" to change often.

Because the Proton’s line-level outputs and headphone jack require some means of adjusting their volume, Wavelength has provided an internal analog volume control that is set via the USB port. According to Wavelength, digital volume controls lose more and more resolution as the level is reduced, so analog volume control is the best solution. When you connect the Proton to a computer, the Proton identifies itself as an audio device that wants to see the full bitstream, unaltered by the computer’s operating system (OS) for the purposes of adjusting the volume. When you set the OS’s volume control to 90%, the Proton sets its internal analog volume circuit to standard line-level voltage, as if it were a device with a fixed output level, such as a CD player. When you use the Proton’s headphone jack, the internal analog volume is controlled by the OS’s volume-control slider. When you adjust that, the OS sends the new setting to the Proton via USB, and the Proton adjusts its analog volume control appropriately.

If you use headphones that need an input level a little higher than line level, the Proton will amplify the input signal when the OS’s volume control is set above 90%. Settings below 90% will attenuate headphone playback volume. Playback software usually includes a volume slider that links to the OS’s slider, but the software may not show the numbers you need to see to ensure that you’ve selected 90% for line-level playback. In that case, opening the Windows speaker volume control or Mac OS X Audio Midi utility will reveal the volume-setting number.

Wavelength Proton


As with other audio components, anything you do to and/or with the Proton DAC makes a difference: which USB cable you use, whether or not you set the Proton on a good equipment rack and/or footers, or if you damp or mass-load the Proton’s top panel -- and, of course, which analog interconnects you use.

Beginning in the 1970s, I dreamed of the day I would be able to hear music without the limitations and sheer fussiness of playing LPs. I preferred listening to LPs rather than CDs until about 2000, when I was finally able to get CD playback that was roughly the equal of analog, though still not the same as analog. It was like the difference between an SUV and a car: both will get you to the same place via the same route, but the journeys will feel very different. Something was still missing from digital playback that wasn’t missing when I listened to LPs -- something nice, something real, something alive. For lack of a better term, I’ll call it soul: that indescribable something that made analog music resonate with me in a way that digital music couldn’t. My $4000 disc-spinning system sounds great, but it lacks the soul I hear when I play LPs.

My Mac-based playback system plus Wavelength Proton was the first digital playback system I’d heard that captured that special something I get from playing high-quality LPs. I felt as if I were listening to the best LPs ever recorded and pressed, but with none of vinyl’s drawbacks: the cleaning, the static, the off-center holes, the various types of warps, the limited channel separation, the vinyl rush, the tracking error, the azimuth error, etc. I now have digital music with soul, and I’m on a huge listening jag. It doesn’t even take the very best recordings to recognize that the missing soul has been restored. It’s there with Country Joe & the Fish, Phoenix, Jefferson Airplane, Coldplay, Joe Cocker, Smashing Pumpkins, the Doobie Brothers, and KT Tunstall. And it’s there with every resolution, from 16-bit/44.1kHz to 24-bit/96kHz.

Thirty years of analog-vs.-digital bickering apparently come down to this: We haven’t had good enough playback gear to hear how good digital recordings can actually sound -- at least not at prices that middle-class audiophiles can afford. I love the Proton DAC because it revealed that digital music can possess the soul of analog sound. It is one of the most significant and revolutionary audio components I’ve experienced since being bitten by the audiophile bug in the early 1970s. The Proton has made the hours I’ve spent ripping CDs to digital computer files on my music-library hard drive worth every minute, and has inspired me to renew my efforts to keep ripping more every day, until every disc I own has been converted.

While trying to get a handle on some concrete things to report about the sound of the Proton DAC, I began to notice differences. "Sing, Sing, Sing," from Erich Kunzel and the Cincinnati Pops’ Big Band Hit Parade (CD, Telarc CD-80177), includes a drum break in which the cymbals are hit so often that a haze of resonances builds up around the discrete sounds of the cymbals being struck by the drummer’s sticks. When I play the CD, that haze of resonances is way down in level; it’s there, but not nearly as clearly and precisely -- I have to listen carefully for it. Playing the ripped track through the Proton revealed just how well Telarc’s engineers captured that haze or bloom (if you prefer) around the cymbals. I’ve listened to that CD for 22 years, but never has the sound of those cymbal resonances been so realistically present.

Through the Proton, the horns on Blood, Sweat & Tears’ first (and, by far, greatest) album, Child Is Father to the Man (CD, Columbia/Mobile Fidelity Sound Labs UDCD II 746), had an indescribable rightness I’d never heard before from this CD. It was as if the horns were glowing with an aural light that just wasn’t there without the Proton. But it wasn’t just the horns. Jim Fielder’s Fender bass walking up and down the scale had a solidity of presence that’s missing with other methods of playback I’ve heard. Even Al Kooper’s piano, which was not recorded nearly as well as it could have been back in 1968, had an indisputable organic presence that is part of the allure of analog, and that I simply couldn’t hear in any digital playback systems I could ever consider buying -- until now.

Another of my favorite recordings is Wrong Way Up, a masterpiece of melody and arcane lyrics by Brian Eno and John Cale (CD, Opal/Warner Bros. 26421-2). Loaded with experimental instrument sounds, this 1990 recording is eminently musical, but the Proton revealed clarity and subtle detail, and such a wonderfully liquid sense of pace that I enjoyed this album even more than before.

The YBA Design WD202 USB DAC ($879), which I reviewed in January, costs nearly as much as the Wavelength Proton, but is more of a digital control center with multiple digital inputs, plus headphone jack and variable volume control. The YBA sounded more or less identical to my disc-spinning front end -- that is, quite good -- but it lacked the Proton’s analog feel. The YBA sounded fine -- until I listened to something I’d just heard through the Proton. The YBA got every digit right, but the Proton got the digits and more right -- something that should be impossible in the bits-is-bits view of digital sound that some digital proponents try to convince us of. One place I heard a difference was in Eno and Cale’s "The River." The YBA so homogenized the harmony vocals that they sounded almost like a single voice; the Proton clearly revealed layers of individual voices.


Wavelength Audio’s Proton USB DAC is not for everyone -- it has only a USB input and stereo analog and headphone outputs -- but it could be a solution for those looking for something to make digital music sound as soulful and right as analog. With the Proton installed, my system, for the first time, made digital music sound like analog, but with none of analog’s drawbacks. Now that I’ve heard this transformation of my system, I will never again be without it.

It’s difficult to heap enough praise on this $900 DAC without sounding like an employee of Wavelength’s PR firm. But if you want your digital recordings to thrill you the way you’re thrilled by a fantastic analog front end, while retaining everything that’s good about digital playback, the Proton is the least expensive way I know of to get there. It delivers ultra-high-end digital sound at a price that’s realistic for audiophiles who can’t consider products that cost many times as much. For its high ratio of performance to price and for its level of innovation, the Proton DAC gets my highest possible recommendation.

. . . Doug Blackburn

Associated Equipment

  • Speakers -- Vandersteen 3A Signature and 2Wq subwoofers (2)
  • Preamplifier -- Belles/Power Modules 28A
  • Amplifier -- Belles/Power Modules 350A Reference
  • Sources -- Pioneer DV-525 disc transport, modified; Perpetual Technologies P1-A/P3-A upconversion-dejitter-DAC combo with Monolithic power supply; Roksan Xerxes turntable, SME-V tonearm (rewired), Cardas Heart MC cartridge
  • Speaker cables -- Audience Au24 e
  • Interconnects -- Audience Au24 e, Nordost Quattro Fil, AudioQuest Carbon USB
  • Power cords -- Audience powerChord e and Au24 e
  • Power conditioner -- ExactPower EP15A feeding Audience aR6-TS
  • Computers (music playback) -- Mac Mini with Intel X-25M Gen2 SSD, FireWire 800 external hard disk, 8GB RAM, running Amarra 2.2; Toshiba laptop running Windows 7, J. River Media Center 15 software
  • Headphones -- AKG K702

Wavelength Audio Proton Digital-to-Analog Converter
Price: $900 USD.
Warranty: Two years parts and labor (nontransferable).

Wavelength Audio, Ltd.
3703 Petoskey Avenue
Cincinnati, OH 45227
Phone: (513) 271-4186