December 2002

Aloia ST 15.01i Stereo Amplifier

by Wes Phillips

We Americans tend to forget that high-end audio knows no boundaries. Oh sure, we know the Japanese make hi-fis -- not just the mass-market stuff, but really special components, such as Nakamichi's Dragon and Stax headphones (er, sorry -- I mean ear-speakers). Then there's Britain, which makes great loudspeakers and turntables, of course -- but they speak English real good there, so they're almost 'Muricans. Holland has van den Hul; France has Jadis, JMlab, and Focal. And Dynaudio is either Danish or German, depending on your point of view.

But Italy? Most US audiophiles would be hard-pressed to name any Italian audio manufacturers. That's a pity, because Italy has a happening audio scene, filled with passionate audiophiles and a bumper crop of homegrown audio manufacturing firms. Among Italian manufacturers, Bartolomeo Aloia is a legendary, all-but-revered, figure -- a man many consider the patriarch of Italian high-end audio.

He is well known among the DIY crowd in Italy as the designer of many tube projects, several of which have schematics available on the Internet (and available in kit form in Italy). Most recently, he has been building extremely luxe components featuring stato-solido technology -- and not just solid-state, but featuring bipolar transistors. The line includes several preamplifiers and three power amplifiers: the 60Wpc dual-mono ST 14.01, the 30Wpc ST 13.01, and the 60Wpc ST 15.01. The latter two utilize outboard power supplies -- available in both inductive and capacitive models.

Sanibel Sound, the American distributor for Aloia, piqued my interest in the $5495 USD Aloia 15.01i (the 15.01 coupled with the inductive power supply) when Steve Davis quietly proclaimed it "as good as anything I've ever heard -- at any price." This from a guy who's selling $40k loudspeakers.

Hmmm.

"How could it be so good?" I asked.

Steve startled me by saying something I've never heard from a distributor. "I have no idea. Maybe it's the inductive power supply. You ought to hear it for yourself."

Indeed.

Fine knacks for ladies, cheap, choice, brave and new

What arrived chez Wes several days later was two boxes -- one heavy enough to make the UPS man grunt, the other heavy enough to make him curse. Me too.

That one was the inductive power supply, which sports a honking huge transformer with multiple windings (right and left channels, plus rectification for each channel). Each winding has its own inductive choke, for a total of four -- the chokes are placed before the capacitors, which is the expensive way to do it. Ayre does it this way in the V-1x amplifier (and in the now-discontinued V-3); Jeff Rowland has used this topology in a few of his designs; so has Cello. However, it's not an easy fix and it makes the final product heavy and costly. Musical Fidelity also uses inductive chokes, but the company places them after the capacitors, which allows them to spec smaller chokes.

Heavy? Oh, yes -- but a class act and quite unusual, even in the rarified world of high-end audio jewelry. The audio-circuit chassis measures 18 3/8"W x 13 1/2"D x 4 3/8"H weighs 23 pounds, while the power supply has the same width and height dimensions but is 11 1/4" deep and weighs 68 pounds.

The audio circuit is extremely well executed. It's essentially a fully complementary FET input/bipolar output emitter-follower triple. In other words, the cascoded FET input drives three parallel bipolar devices (emitter-follower driving emitter-follower driving emitter-follower -- and remember, the circuit is complementary, so each channel's parts count needs to be doubled).

The zero-feedback power regulators are also cascoded -- obviously Sig. Aloia likes cascodes. The amp has a DC-sensing protection circuit.

Both chassis are extremely handsome. Their faceplates have large expanses of brushed aluminum interrupted by curved anthracite panels that project bay-window-like from their centers. In the case of the chassis containing the audio circuitry, the panel has a centrally located silver power button, which is surrounded by an indicator that glows red when the power is engaged.

The power supply's back panel has an IEC power socket, the on/off switch, and a hard-wired umbilical sporting an oblong multi-pin connector which fits the 15.01i amplifier.

The amplifier proper has the multi-pin power supply jack, two sets of what appear to be WBT binding posts, and two high-quality gold-plated RCA inputs. The omission of balanced XLR connections might strike some as odd, but while complementary operation unquestionably reduces spurious noises from invading circuits, audio designers disagree on its utility as a connection scheme in home-audio applications. An Aloia Data Link pass-through, utilizing phone-connectors, completes the rear panel's inventory.

To call the Aloia 15.01i impressive-looking would be taking understatement too far -- it's beeyootiful. Its livery is as elegant as anything being produced, and it has a tank-like stolidity that should inspire confidence. It is impeccably constructed and sports a mix of "superstar" audiophile parts with less glamorous components, leading me to suspect that Sig. Aloia chose the parts for the way they sounded in this circuit, rather than simply specifying the most expensive examples in each category (a trait he shares with manufacturers such as Mark Levinson Audio Labs, Conrad-Johnson, and Ayre). And while the 15.01i's circuit certainly owes little to anyone's "amplifier cookbook," it doesn't chuck out the last century of circuit design development, either. Sig. Aloia has obviously called upon his lifetime of audio knowledge to create a product as individual as he is.

Oh, yes, one last detail. You'll note that I called the 15.01i a 60Wpc amplifier -- that comes from Aloia's published specs, which state that the amp produces "60W/minimo per canale (8 ohm)." Apparently Sig. Aloia believes in modesty: the ST 13.01 is rated at 30Wpc minimo, but has been measured producing a clean 75Wpc; Sanibel Sound reckons the 15.01i could easily deliver 125Wpc. Output was certainly never an issue in my audition of the amp. Unless you have a speaker that only a handful of amplifiers can drive (in which case, you know you need to choose carefully), you're probably safe assuming the 15.01i is mighty enough to drive yours.

Choice has always been a privilege of those who could afford to pay for it

I received the Aloia ST 15.01i just days before having to pat the Dynaudio Evidence Temptations on their bottoms and send them home to Chicago, so I wasted no time connecting the amp to the big speakers. Not only are the Temptations the finest speakers I've had in my listening room, they're an interesting test of amplifier fortitude (which, if English were like German, would probably be called something like amplitude) -- it doesn't take much to drive 'em, but it takes grunt to make 'em really sing.

The ST 15.01i made choirboys out of the temperamental towers, transporting the huge sound of Mozart's Requiem (Philharmonia Orchestra, Giulini, cond.; Helen Donath; Christa Ludwig; Robert Lloyd [Angel Classics 73702]) into the room. What a great performance -- both from my hi-fi and the musicians. The more I listen to this 1978 recording, the greater my love for it. It's deeply felt, but its drama only gains power from its extraordinary restraint. The soloists are top-drawer -- in the Tuba mirum, Lloyd actually manages to overpower a particularly rude-sounding trombone.

The sound was burnished and powerful. The bass was forceful and quite deep, while the string sound seemed illuminated from within. The voices, especially Christa Ludwig's, sounded sublime. Without question, the Aloia ST 15.01i was a winner right out of the box.

When the Dynaudios did finally go walk-about, I auditioned the Aloia amp in a variety of system combinations, including ones with the Roman Audio Centurion, ProAc Response One S, and Polk LSi15 speakers; Ayre K-1x and Conrad-Johnson Premier 17LS preamps; and an Audio Research CD3 CD player. I employed AudioTruth Midnight and DiMarzio M-path interconnects and speaker cables, or Shunyata Research Aries and Stereovox SEI-600 interconnects. Shunyata Research's Hydra power-distribution center and Shunyata Research Taipan AC cords handled the power duties.

In choice, ... so oft beguiled

The most distinguishing impressions I developed about the Aloia concerned its creamy presentation and burly bottom end. That sounds a bit like a paradox, but the ST 15.01i reminded me of the classic Krell KSA-50 in that it combined a forceful tonal presentation -- one which had me pulling out disc after disc muttering, "I never heard this sound so powerful!" -- with a sweet, detailed midrange, and seductive upper-frequency sound.

It's one of those amps you could listen to for hours. I'm generally sensitive to amplifiers that tend to add coarseness to upper string tones -- long before I am consciously aware that I'm not completely enjoying myself, my shoulders get tired. After a few years, it finally sunk in that tired shoulders equal shrill sound, so now I pay particular attention to the kinesiology of my upper trapezius. The Aloia ST 15.01I never got a rise out of 'em. (Not only might you react differently, you probably do -- but I believe in working with the tools you've got.)

One of my new favorite discs for system dissections is Tony Faulkner's recording of Shostakovich's Symphony No.11 by the London Symphony Orchestra under Rostropovich [LSO Live LSO 0030]. I heard the DSD master when I was in London, and while the CD doesn't begin to match that, it's still head and shoulders above most other compact discs. The disc is full of life and power, with huge brass choruses and crisp snare drums rat-a-tat-ing away and tympani creating a forward pulse that sounds almost organic. And the Aloia certainly made the most of the sweep and the life embedded in the CD's pits -- the attack of the sticks striking the heads of the snare drums was crisply articulated, and fast and sharp. And the brasses, particularly the trombones and tubas, sounded incredibly lifelike and present.

However, the Shostakovich highlighted an area where the Aloia did not excel -- for all of the power and life and sheer loveliness of the sound, the soundstage seemed somewhat insubstantial. Not small, not flat, simply less than convincing.

It was time to try different system situations with the Aloia -- and it was time for some comparisons.

Happiness is a choice that requires effort at times

Changing system components certainly did make life more interesting. The ST 15.01i played well with the Conrad-Johnson Premier 17LS, but less so with the Ayre K-1x. Tubes traditionally have done better than solid state at soundstaging, after all.

If you think that audiophiles obsess waaay too much about cables, you'll get no argument from me -- but the Aloia amp made all the claims concerning the vast differences between speaker cables seem completely credible. Not so much with interconnects (although I could clearly discern differences among them), but astonishingly so with speaker cables.

The answer could lie in something that happened when I connected the Aloia to the Roman Audio Centurions. I had been listening to a variety of discs and was wondering if I had managed somehow to fry a tweeter goosing the system to "lifelike levels" on the Barenboim/CSO Le Sacre du Printemps [Teldec 8573 81702-2]. I wasn't at all happy with that morning's sound, which was not nearly so limpid and refined as I had been getting previously. In fact, it was downright harsh.

I walked over to the speakers to examine their large soft-dome tweeters, when I saw that my cat had tried to walk through the venetian blinds and had become entangled in the slats. I leaned over the Aloia's audio circuit chassis to free the dummy and felt waves of heat rolling off the amp's heatsinks. I touched my finger to a sink and jerked it away -- that sucker was hot!

I powered the unit down and spent a few hours trying to figure out the problem. The Centurions worked fine with the Ayre V-5x and the Linn Klimax Twin -- all the harsh hashiness I had objected to earlier faded like the mist on a sunny morning. I ran the Aloia disconnected from the system for a few hours and it remained at room temperature the whole time. I changed cables between the Aloia and the Centurions (from DiMarzio M-Path to Shunyata Research Lyra) and everything seemed fine -- at least the amp didn't throw off unusual amounts of heat.

At the time, I simply wrote the Aloia/DiMarzio/Roman Audio combo as a bad match, but long afterwards I spoke to Ayre's Charlie Hansen concerning his use of bipolar transistors in the V-5x. He used them because he thought they sounded better than FETs, he said, but there was a trade-off designers have to design around.

"It seems that bipolar transistors are inherently unstable devices," Hansen told me. "That doesn't make any sense to me.… A bipolar is an emitter-follower [having] a gain of less than one, so how could it oscillate? Somehow, [bipolar transistors do oscillate] if you hook up a capacitive load, which, of course, is essentially what a speaker and, especially, speaker cable are."

Hmmm. One difference between speaker cables is their capacitance. Hmmm. The Roman Audio Centurions are not your ordinary load -- despite their efficiency, they aren't a cinch to drive. Is it possible that a particular speaker/cable combination could represent a load that could drive a bipolar amplifier into oscillation? Not being able to ask Sig. Aloia, I put the question to Hansen.

"Oh sure, it could happen. But one thing I've learned is that theory doesn't necessarily count as much as implementation." That's the rub, of course, it all comes down to how a product actually works, not how it's supposed to work. And if we've learned one thing in the realm of ultra-high-performance audio, it's that everything makes a difference, and when a designer as experienced as Sig. Aloia chooses a circuit design, output device, or passive component, it's usually the result of careful consideration of performance versus consequences. Let's just leave it, as always, with the admonition to try the amp at home in your system before determining if it's the one for you.

I have my choice: who can wish for more?

Since I was reviewing the Ayre V-5x for SoundStage!, I concentrated on comparing it to the ST 15.01i. With chamber music, such as the delightful Music for a Glass Bead Game [John Marks Records 15] by Arturo Delmoni and Nathaniel Rosen, the two were extremely well matched and, in some ways, such as its deep, sonorous portrayal of Rosen's earthy tone, the Aloia was slightly more ravishing.

But although Delmoni's violin tone was far from astringent through either amplifier, it was marginally sweeter on the ST 15.01i -- sweet, yes, but robbed, albeit ever so slightly, of some of its natural brightness. And, in the Bach Two-Part Inventions, which are textbook examples of the varieties of touch and tone at the disposal of these two master musicians, the Italian amp missed some of the subtle shifts in texture and emotion, ever so subtly flattening the tonal and dynamic palettes.

"Jungle Man" from The Very Best of the Meters [Rhino 74642] built upon this impression. The song is pure funk -- basically it's a chant repeated over a bass and drum groove embellished by piano and guitar fills. There's not much happening melodically, harmonically, or dynamically -- what's fascinating is the way Ziggy Modaliste continually shifts the downbeat behind George Porter, Jr.'s bass line. The fluidity of that rhythmic interplay, however, is phenomenally complex, and the sinuously inventive energy of that initially repetitive-sounding groove is comprised entirely of fits and jerks that very few musicians could re-create.

Not many hi-fis can, either. This sort of nimble dance of contrasting elements is something the V-5x is almost unrivaled at. It just skitters along, riding the changing dynamics and temporal relationships. In other words, it makes you want to dance.

And the Aloia didn't. For me, at least. Nod my head, tap my foot, waggle my finger -- well, yes. Quite subtly, it flattened the affect ever so slightly. But when dealing with such an ephemeral question as who put the bomp in the bomp-she-bomp?, it doesn't take much to turn something real into something insubstantial.

The Aloia ST 15.01i is powerful and delivers music almost entirely intact. Harmonically and timbrally, it is an extremely refined performer. I think it tends to lose just a smidge of resolution compared to amps such as the Ayre V-5x or the Linn Klimax Twin. The sweetness or creaminess or seductive sound it delivers is, I suspect, not so much a coloration (for it doesn't sound colored at all) as it is the loss of extremely minute details such as the shadings in Modaliste's and Porter's constantly shifting interplay or the extremely soft high harmonic overtones of Delmoni's fiddle strings. Of course, it all depends on what you value in musical reproduction.

Some of those evanescent details that I feel the Aloia discards are the same ones that can cause notes to clang and chitter against one another. No matter how mellow the fundamentals of two notes might seem, the relationships between their overtones can get downright noisy -- and while I take that as a sign of low-level resolution and actively seek out equipment that reproduces that clangor, you might just as rightfully claim that it's noise and choose not to have to hear it.

Important decisions should be governed by the deep inner needs of our natures

I liked the Aloia ST 15.01i. It is as well built as anything I have ever auditioned, and it certainly has the look and feel of the very first rank of high-end audio componentry. It has a powerful, smooth, easy-to-like presentation of music that will appeal to many listeners. Bartolomeo Aloia has built an unusual and thought-provoking amplifier in the Aloia ST 15.01i, one that, I suspect, shares many traits with its progenitor. I've never met the gentlemen, but based on the ST 15.01i, I would guess he is deliberate, strong, and always pleasant.

In almost every comparison I've cited, the differences between the Aloia and other high-performance power amplifiers have been extremely subtle. Just as every listener is different, every system is also different. The ST-15.01i's sound quality seemed more synergistically interactive with its companion components than most amplifiers I have auditioned, but what that means is best left to each listener to assess. By necessity, a large number of products pass through my audio system each year; some listeners might very well decide to build a system to play to the Aloia's strengths of listenability and suavity.

After all, even in audio, there's a big world out there. It's nice to see more of it than just our tiny corner.

...Wes Phillips
wes@soundstage.com

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