Art Dudley Listening

Reconnecting the review sample to my Apple iMac (OS 10.6.5 at present) was, as they say in Bristol, a doddle. And I prepared for the experience by loading up on high-resolution music files, including some of the great 24-bit/176kHz Rolling Stones offerings on HDtracks.com. But therein was the hoop through which I still needed to jump: Before changing from one music-file sampling rate to another, Mac users must exit iTunes entirely, pull up the Apple Midi utility, manually select the new rate, then launch iTunes—every time. (Good heavens: Next they'll have us flipping our records and plucking the dust from our needles!) For that reason, and to investigate the claims of better sound from hi-rez files, the time had come for me to try some alternatives to Apple iTunes.

Rip it all hairier
When talk turns to Mac-specific playback software, Pure Music, Decibel, and Amarra are the names that come up most often. All three are designed to work with rather than replace iTunes, which retains the job of cataloguing your music; Pure Music, Decibel, and Amarra take over the front-end playback chores.

I began with Pure Music (v.1.74), which sells for $129 and can be downloaded for a no-charge 15-day trial period from Channel D Software's website (footnote 2). Features include Memory Play (a term synonymous with cache or solid-state play, meaning that the file is loaded into memory from the disk before playback begins), and the ability to automatically change sampling rate on the fly, from one file to the next. Pure Music allows sampling rates of up to twice the 192kHz limit of the other two playback programs, and even includes a reverse-play feature for those of you who wish to be reminded that Paul is, in fact, dead.

As with the other two aftermarket programs, downloading and installing Pure Music created its own onscreen icon, which assumed a position on my Mac's application dock; clicking that icon launched iTunes first, after which the Pure Music user interface was added to the left side of the screen. Going from iTunes to Pure Music, the sonic improvement was modest but worthwhile, the most immediately obvious change being a general cleaning-up of the treble range. Cymbals in particular sounded less hashy, and well-made recordings seemed more open and "airy." The piano sound in Jorge Bolet's recording of Liszt's crazy piano transcription of Wagner's overture to Tannhäuser—from Rediscovered: Liszt Recital (CD, RCA Red Seal 63748-2)—was more naturally "stringy" and colorful, and each note seemed to have more acoustic space in which to unfold and die. By contrast, iTunes had a grayish sound—although Apple's free software delivered a satisfying degree of musical momentum and pitch certainty. But before long, Pure Music proved that the latter, too, could be bettered. With live recordings, such as Hot Rize's So Long of a Journey: Live at the Bouder Theater (CD, Sugar Hill 3943), the subtle pitch variations that signal the spontaneous and altogether human sound of live singing were clearer than through iTunes.

Pure Music was easy to use, if not perfectly quirkless. Whereas iTunes changes the central control-button symbol from Play to Pause during playback, Pure Music did not. (To stop a track in Pure Music, one presses Play yet again, upon which the Pause symbol flashes into view for a fraction of a second.) In Memory Play mode there were slight pauses before files began playing—sampling-rate changes were also occasioned by brief pauses—but this was equally true of the other two aftermarket programs, and seemed reasonable enough.

Stephen F. Booth's Decibel (v.1.0.2) sells for $33, and can also be downloaded free of charge for a limited-time demo. Unlike Pure Music and Amarra, Decibel didn't need iTunes to be launched at all: Booth's software has its own graphical user interface—plain, simple, unburdened with luxuries—and the Decibel playback engine found the music in my iTunes library without a hitch. (The main Decibel screen is like a blank sheet of ledger paper, to which I could add playlists and individual songs, as desired.) Memory play and other options were selected from pulldown menus, FLAC files were handled natively, and sampling-rate changes were handled automatically—although in one isolated incident I clicked on a file of higher resolution than the ones I'd been playing and Decibel sulked in silence, requiring me to quit and relaunch the program. On subsequent attempts it worked flawlessly.

In my system, Decibel sounded even clearer and more open than Pure Music. Again: The step up in sound quality from iTunes to Pure Music wasn't enormous, and going from Pure Music to Decibel was a similarly modest move. But when I went back and compared Decibel with iTunes, the difference seemed considerable—and surprisingly so. Compared with Decibel, music played by iTunes sounded smoky and gray, with more artifice and haze attached to the highest treble sounds. Indeed, music files sounded a bit clearer and more open when played with Pure Music, but Decibel opened up them up even further, like an audio prybar. When I first heard Gary Brooker's familiar voice singing "Fires Which Burnt Brightly," from Procol Harum's Grand Hotel, I was astounded by the degree of sonic obfuscation I had subconsciously trained myself to accept and listen through: Decibel scooped away the gray sonic dust filling the spaces that should have been empty, so that pitches and timbral colors alike were clearer and more distinct.

I was so impressed with this crazy-cheap software that I asked its developer, Stephen F. Booth, to explain what makes Decibel so special. Booth replied that his design goal was simple: "Perform as little processing on the audio as possible, and provide the shortest path from the file on disk to the DAC while preserving the file's bits." He continued: "I knew I needed to avoid software sample-rate conversion. This implied that I would need to automatically set the DAC's sample rate for each file. I'm not scared of conversions to and from floating point, but I knew they would need to be accurate, so I decided to use doubles (64-bit floating-point numbers). While all sample sizes up to 24-bit can be converted to and from 32-bit floating-point numbers without loss of accuracy, I decided to use 64-bit for two reasons: they can be faster on 64-bit processors, and future-proofing. Who knows if or when 48-bit PCM will become the norm?" Not me, that's for darn sure.

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Footnote 2: Pure Music offers a subset of the functionality of Channel D's Pure Vinyl program, which Michael Fremer enthusiastically reviewed in August 2010.—Ed.