PrimaLuna ProLogue Eight CD player
By John Atkinson and Fred Kaplan   •   July, 2008 There's a retro, Heathkit vibe to the curiously capitalized PrimaLuna ProLogue Eight CD player: a shelf of glowing tubes and a chunky transformer case perched atop a plain black chassis. But on closer inspection, it seems there's much more going on here. The chassis is made of heavy-gauge steel, with (according to the manual) a "five-coat, high-gloss, automotive finish," each coating hand-rubbed and -polished. The tube sockets are ceramic, the output jacks gold-plated. Inside, separate toroidal transformers power each channel. Custom-designed isolation transformers separate the analog and digital devices, to reduce noise. The power supply incorporates 11 separate regulation circuits. The output stage is dual-mono with zero feedback. Audio-handling chips include a Burr-Brown SRC4192 that upsamples "Red Book" data to 24-bit/192kHz, and one 24-bit Burr-Brown PCM1792 DAC per channel. Only the tiny silver control buttons (on the otherwise hefty faceplate of machined aluminum) betray a whiff of chintz.

In the early days of CD, a few tube-powered models came on the market; the idea was that the dimensionality and warmth of tubes would drape a cuddly blanket over digital's flat harshness. Digital has come a long way since then, and in any case the tubes in the ProLogue Eight aren't about smoothing over; they are, or purport to be, about greater accuracy. Not only is the Eight powered by a pair each of 12AX7, 12AU7, and 5AR4 tubes; its internal clocking device is a mini-triode tube instead of the solid-state oscillator found in most CD players. The claim is that a tube clock introduces less noise and jitter into the CD drive and the DAC chip, resulting in superior detail, dynamics, and musicality. I have no idea whether there's any technical basis for this claim. Nor could one judge simply by listening, without taking out the triode-based circuit, inserting a conventional oscillator, and noting the difference (if any, footnote 1). Still, based on what I did hear, I suspect there might be something to it.

Fred's setup
I connected the PrimaLuna to the Krell FBI integrated amplifier, which in turn fed the Verity Audio Parsifal Ovation speakers. Nirvana cables were used throughout. The PrimaLuna comes with a cage to cover the tubes, but I listened with the cage removed, mainly because it looked nicer. (I didn't notice any sonic difference.)

A note, perhaps, about quality control. The tubes are said to last 10,000 hours. (They're warranted for six months.) But on my review sample, long before that time span, one of the 12AX7s went bad—one channel suddenly sounded fuzzy with occasional crackling, a problem fixed by replacing the tube. Also, once, when I lifted the front of the player a few inches to place beneath it a Black Diamond Racing Cone (without turning the player off), one of the 5AR4 rectifier tubes started to flare. These instances may have been flukes; tubes are sometimes troublesome.

Speaking of those cones, they made a substantial sonic difference, more so than with most electronic gear. Without the cones, bass sounded considerably flabbier and transients less crisp. I noticed this in what was as close to a double-blind experiment as a person can conduct by himself. After listening for a while to a different CD player, I put the PrimaLuna back in the system but forgot the cones. It sounded worse (flabbier, less crisp) than I'd remembered. Then I noticed the missing cones. I put them back underneath, tips down, et voilà! Back to normal.

Fred on Sound
What was normal for the ProLogue Eight? I'm tempted to say, "About what one would expect of a $2500 CD player powered by tubes." Actually, it was better. The good things we've grown accustomed to hearing from tubes were all there: gorgeous midrange, sweet strings and saxophones, lifelike female singers, a soundstage with acres of depth. The deficiencies common to budget-priced tube units were there, too—tepid bass, rolled-off highs—but not nearly to the degree you might expect. Or, to the extent they were there, they were handled or offset in ways that made them less audible, certainly less objectionable. I think this is where that triode clock comes in—or, at least, some design feature that yields the same alleged effect.

One good test of bass, as I've noted elsewhere to the point of (some readers') exhaustion, is the first minute of David Zinman and the London Sinfonietta's recording of Górecki's Symphony 3 (CD, Elektra Nonesuch 79282-2), during which the double-basses sound out the melody in an octave so low that, on some systems, you can barely hear them at all. With the PrimaLuna, I couldn't hear the actual values of the lowest notes, but I could hear the attack of the bows and the harmonic overtones. In other words, I got a sense of the bass line; unless I'd heard this album on other, better CD players, I might not even have been aware that the bass was rolled off.

Similarly, at the start of "Mood Indigo," on Duke Ellington's Masterpieces by Ellington (CD, Columbia/Legacy CK 87043), I couldn't identify all the lowest notes that the bass player plucked, but I did hear the pluck. And since that pluck has a lot to do with the music's rhythm, dynamics, and emotional drive, I'd rather hear a pluck without the precise note than vice versa. On James Carter's tribute to Django Reinhardt, Chasin' the Gypsy (CD, Atlantic 83304-2), I could hear the guitarist's strummings, even if I couldn't quite hear the full body of the guitar. On the Maria Schneider Jazz Orchestra's Sky Blue (CD, ArtistShare AS0065), I didn't hear the cymbal's full shimmer, but I did hear the percussive edge of the drumstick hitting it. On Lorraine Hunt Lieberson's lovely disc of two Bach cantatas (CD, Nonesuch 79792-2), her slight sibilance on consonants— g, k, ch, and so forth—cut through distinctly. Without such clarity, sung words are unintelligible.

The ProLogue Eight didn't get all the subtlest transients quite right. When Erik Friedlander rapidly plucks the cello on his wondrous solo disc, Block Ice & Propane (CD, SkipStone 371013742), a CD player like the Krell Evolution 505 lets you hear not only his most intricate fingerwork but also the relative thickness of each string and its resistance to his plucking. The PrimaLuna didn't. Then again, the Krell costs four times as much.

The ProLogue Eight's shortcomings are more apparent with some recordings than with others. On the Lieberson disc, the double bass wasn't distinguishable from the organ; that reedy sound of the organ's pipes was obscured by sounds of a similar pitch. And while the depth of the recording venue was nicely captured (the oboe seems to be way back there), there wasn't much sense of air between the instruments from side to side.

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Footnote 1: PrimaLuna's website is bereft of any details about the SuperTubeClock circuit, and a white paper I had been promised by PrimaLuna engineer Marcel Crouse had not materialized by the time this review went to press. In theory, there should be no change in the behavior of an oscillator circuit due to the nature of the active device, other than the higher available gain from solid-state devices allowing a higher Q, or Quality Factor. Looking at the circuit board, there is a crystal directly adjacent to the miniature triode, so I assume the tube is used in what would otherwise be a conventional crystal oscillator circuit.—John Atkinson