Stello Ai500 Integrated Amplifier
Im not quite 30 years old, but
technologically speaking, I feel like a dinosaur. In an age when I can download almost any
song or album I want, Id rather visit my favorite record shop after work on Friday
and sift through the stack of new arrivals to see what treasures are being pressed on
vinyl. When I was saving money last year to buy a turntable, it seemed everyone around me
already owned an iPod. More times than I can remember, friends asked, "Do they still
sell records?" The way I collect music makes me an outlier among my peers.
A friend visited recently and commented that my stereo
sounded good for a two-channel system. It was the first time Id heard someone
apply a caveat to stereo, as if it were obviously inferior to surround sound. I realize
now that, in a 5.1-channel world, some people consider two-channel sound a compromise.
Clearly, something needs to be done to change that perception.
Im a firm proponent of a simple, good-quality,
two-channel system for music playback. This is partly due to the number of high-quality,
superb-sounding integrated amplifiers Ive reviewed. For as little as $500, its
entirely possible to buy a musically pleasing integrated amplifier that can be enjoyed for
many years. If a buyer can spend more -- say, $3000 to $4000 -- he or she can own a
component that will compete favorably against high-end separates with very little
compromise in performance. This is the world of a product such as the subject of this
review, the Stello Ai500 integrated amplifier ($3495 USD), which comes from April Music of
April Music began making audio components in 1998. Before
that, owner Simon Lee had imported high-end audio gear into Korea. Over time, Lee had
grown unhappy with the escalating prices of audio products whose performance was not on a
par with their cost, and had decided to introduce a line of audio components that would
compete with other high-end brands, but at reasonable prices. Today, April Music makes
several product lines; in ascending order of price, these are: the affordable but very
chic Aura products (including the Model One speakers), the Stello 100 series, the more
upscale Stello line, and the state-of-the-art, cost-no-object Eximus series. Based on the
praise Lees products have received from SoundStage! Network writers and others,
hes been very successful at meeting his objective.
In his Stello line, Lee has attempted to offer much of the
performance of his Eximus products at considerably lower prices, and the Ai500 integrated
amplifier is a perfect example. Built as sturdily as any integrated amplifier Ive
ever seen (including some that cost thousands more), its the type of component
youll be happy to display in your equipment rack; its gorgeous, brushed-aluminum
finish and soft curves will make it at home in any contemporary setting.
When I first pulled the Stello from its box, I was struck
by its weight. At 35 pounds and measuring 18.1"W x 3.4"H x 15.7"D, the
Ai500 is a substantial piece of kit, due in large part to the oversized 800VA toroidal
transformer and 90,000mF of capacitance it uses to generate the enormous amounts of power
its claimed to output: 150Wpc into 8 ohms or 300Wpc into 4 ohms. With numbers like
these, the Ai500 seems ready to power just about any speaker youd ever want to
partner it with. Its class-A/B output stage uses matched Hitachi MOSFET power transistors
in a push-pull configuration that, in conjunction with careful ground-isolation
techniques, are said to ensure a high signal/noise ratio.
The Ai500s rear panel boasts numerous inputs for
connecting your entire system. In addition to one set of Neutrik balanced inputs are three
single-ended inputs: one each for a CD player, tuner, and an auxiliary component such as a
phono stage. A Bypass input sends the signal directly to the amplifier stage, allowing the
user to experiment with external two-channel preamplifiers, or to use the Ai500 to power
two channels of a home-theater system. Theres also a Record input for connection
with a cassette deck. The Ai500 also comes equipped with a preamplifier output for use
with an external power amplifier, either separately or in conjunction with the
Stellos own power section. Otherwise, the preamp out can be connected to a subwoofer
to augment the low-end output of a stereo pair of speakers.
Another standard feature is an onboard digital-to-analog
converter (DAC) that allows you to connect to the Stello the digital output of a CD or DVD
player, or a computer. Three digital inputs are provided: coaxial, optical, and USB
(16-bit/44.1kHz only). There are also analog and digital inputs for an iPod docking
station. Using a USB control cable, its possible to scroll through the music on your
iPod using the supplied remote control. However, since the iPod is connected with stereo
analog inputs, the iPod itself converts its digital datastream to analog, not the
Ai500s onboard DAC. Still, if your music is stored primarily on your iPod or the
hard drive of your computer, Stellos Ai500 offers the most simple, direct means of
playing it that I have seen in an integrated amp.
The front panel has a clean, simple appearance. A small
display tells you, in red text, which input is selected and the volume at which it is set.
The displays brightness can be set to Low, Medium, High, or Off. Under the display
is a row of buttons labeled (from left to right) Balanced, CD, Tuner, Aux, Digital,
Bypass, and Mute. Volume is controlled with a large rotary dial at the far right that
employs a Cirrus Logic CS3310 digital volume control, adjustable in increments of 0.5dB.
The volume can be set and adjusted independently for each input -- a handy feature for a
reviewer who wants to match gain levels to compare different components. The main Power
button is on the far left.
A full-function remote control is included. Made of
aluminum, its divided into three sections: one for controlling the matching CDA500
CD player (as yet the only other member of Stellos 500 series), one for navigating
the music stored on your iPod, and one for controlling the Ai500 itself.
Every aspect of the Ai500s build exudes quality. From
the quality of the connectors to the speaker binding posts (which accept bare wire, spade
lugs, banana plugs, or pin terminals), April Music appears to have thought of everything
to put in the Ai500 -- except for an onboard phono stage. That wont affect most
listeners, but it will affect some, like me. Still, the Ai500 exemplifies the flexibility
possible in an integrated amplifier.
But at $3495, the Ai500 needed to do more than just look
I inserted the Stello Ai500 into a system comprising PSB
Platinum M2 bookshelf speakers, an NAD C542 CD player, AudioQuest Type 4 speaker cables,
and Kimber Kable Tonik interconnects. To test the Stellos DAC section, I connected
the NADs digital output to the Ai500s coaxial input using an AMX Optimum AVC
When I started listening to the Stello Ai500, it
didnt make a huge impression. The sound wasnt bad per se; it just didnt
jump out at me. In fact, I had a very difficult time trying nail down its sound at all --
it took me some time to realize that I was listening for something that wasnt there.
The Stello Ai500 didnt really have a sound of its own. It was dead neutral.
The trouble for a component that produces few or no sonic
colorations is that a listener might ignore it in an audio showroom. It takes time to
appreciate the fact that the lack of a sound of its own is actually a high-end
components best possible attribute. This described my experience with the Ai500.
When at last I stopped fretting over what to write about in the review and just started
listening to music, I found myself picking up a pen and scribbling listening notes.
This first happened when I placed in the CD tray my
well-worn copy of Radioheads Kid A (CD, EMI 5 27753 2). As I listened to
track 1, "Everything in Its Right Place," I was impressed with the size and
coherence of the soundstage. From top to bottom, the Ai500 was one of the
cleanest-sounding integrated amps Ive ever heard. Unless the recording itself was
poor, the Stello provided an amazingly clear, wide-open view into the music. Ive
never heard such crisply defined images outlined in front of me.
As I continued listening to Radiohead, the horn section in
"The National Anthem" was truly raucous, but the shrill screeches and blaring
lines were wonderfully invigorating -- they certainly werent warm or fuzzy, but
neither did they sound piercing or harsh. Rather, they remained clear and comfortable to
hear, and even prompted me to turn up the volume. In fact, the Ai500 is the first
integrated amplifier Ive heard since reviewing the Bryston B100 SST in 2006 (and
which I ended up buying) that consistently had me turning up the volume -- everything that
emerged from the speakers was more of what I wanted to hear, and I never felt the
discomfort that comes when music is too loud. Of course, this isnt to suggest
that the Stellos volume could be turned up indefinitely; sooner or later, things got
uncomfortable. But when an amplifier sounds great at low volumes, and retains the same
sonic virtues without added unpleasantness at higher volumes, its a very good sign.
The clarity of the Ai500s sound meant that it was
able to retrieve incredible levels of detail. The rattle of the tambourines metal
plates during the driving rhythm of the apocalyptic "Idioteque," from Kid A,
was as pristine as Ive ever heard. Even the sense of space around the instrument was
tangible -- it sounded as if it were right in front of me. I dont recall ever
hearing such minute detail so clearly, and that summarizes much of my experience with the
Detail never sounded forced or artificially highlighted, as
though a spotlight had suddenly been shone on one aspect of the music. Sometimes a
component will emphasize the highs, thereby exaggerating the level of detail in a
recording. Not only can this become fatiguing over long periods, it also lends itself to a
more analytical sound. The Ai500 was not analytical but eminently musical. Its ability to
clearly delineate the voices of Elliott Smith and Rebecca Gates on "St. Ides
Heaven," from Elliott Smith (CD, Kill Rock Stars krs246), was exceptional. The
solidity and separation of their voices was beyond reproach; again, the musicians seemed
to be in the room with me.
The Ai500 consistently provided rock-solid, unwavering
images across the soundstage. In fact, rock-solid seemed to describe its
performance overall. I cant attest to whether or not the Ai500 met its specified
power ratings -- I lack the appropriate test equipment -- and I was never close to pushing
it to its limits, but it always had heaps of power, and gave me the feeling it had plenty
in reserve. Unless you have a huge listening room, terribly inefficient speakers, and/or
you play your music at volumes that wake the neighbors, its unlikely youll
ever exhaust the Ai500s power capacity.
Typically, a good power supply manifests itself in strong
bass performance, and Im happy to report that the Ai500 was not an exception. Much
like the rest of the spectrum, the low end sounded wonderfully detailed and clean, but it
could also hit with plenty of impact, exhibiting some warmth and bloom in the process. On
the Great Lake Swimmers "Backstage with the Modern Dancers," from Ongiara
(CD, Nettwerk 30691 2), I could almost feel in my chest the thump of the kick drum as the
Ai500 coaxed full, powerful bass from my bookshelf speakers 6.5" drivers. This
was even more apparent with Massive Attacks "Angel," from Mezzanine
(CD, Virgin 45599). The song opens with a bass line that isnt even audible through
my speakers until a few seconds after it begins, so deep are the low frequencies. However,
when they did start to become audible, I could feel them through my whole body as they
radiated out from the speakers and into the room, flooding it with the dark murk
characteristic of this superb trip-hop album.
Overall, there was little for me to criticize about the
Stello Ai500s "sound" -- or lack of it. Some listeners might want a little
more warmth and bloom in the low end, while others may prefer a more forward, more
immediate sound. Not I. This integrated amplifier struck the perfect balance between tonal
neutrality, exceptional transparency, and explosive dynamics, the last likely due to its
beefy power reserves. To my ears, the Ai500 is the best integrated amplifier to come along
since the Bryston B100 SST -- which I discuss next.
|DAC in the Box
Standard equipment with the Ai500 is what Stello describes as
"an ultra high performance digital-to-analog converter capable of elevating your
computer audio files to true high-fidelity performance." Because I never listen to
music directly from my computer (presently, only two CDs are copied onto the hard drive),
I didnt test this claim, although I did play a number of CDs using both the NAD
C542s DAC and the DAC aboard the Ai500.
As I switched between the two DACs, the differences I heard
between them could be described as ones of addition and subtraction. As I went from the
NADs DAC to the Stellos, it was as if there was an added sense of space in the
music -- as if the stage had opened up more in front of me. This made it easier to hear
into the music, and gave the Stello a slightly better see-through quality. Listening to
Spiritualizeds Ladies and Gentleman We Are Floating in Space (CD, Dedicated
07822-18974-2) through the Stello DAC, the stage just seemed to grow out to the sides as
well as to the back. Returning to the NAD, it was as if the music had been scaled down and
shrunken a bit.
The two DACs bass performances were very similar --
both exhibited fully fleshed-out low frequencies. Here again, however, the Stellos
bass was slightly firmer than the NADs, as I heard while listening to the bass
guitar in "If You Could Read My Mind," from Gordon Lightfoots Complete
Greatest Hits (CD, Warner Bros./Rhino WTVD 78287), which was a bit cleaner in its
extension through the Stello.
The differences between the NAD and Stello werent
enormous. The NAD still achieves most of what the Stello does, although any disparities
between them favored the Stello. If I owned a Stello Ai500, Id definitely choose its
digital conversion over that of the NAD C542. However, the Ai500s DAC will probably
be even more appreciated by listeners who store their music on a hard drive and want to
improve the sound from their computers. Given that the Ai500s DAC comes standard, it
gives the Stello a big edge over some of its competitors.
. . . Philip Beaudette
Regular readers will know that Ive been a big fan of
the Bryston B100 SST ever since I reviewed it three years ago. In fact, I liked it so much
that I spent the year following that review saving up enough to buy one for myself.
Ive spent considerable time listening to many high-end integrated amplifiers since I
began writing for the SoundStage! Network, and during that time nothing has impressed me
as much as the Bryston -- until now. The Stello Ai500 plays in the same league as the
Bryston and, to my ears, improves on it in some areas.
The Stello and Bryston are similarly priced. The basic B100
SST costs $2995; adding a remote tacks another $400 onto the price, while the optional
onboard DAC costs an extra $1000. That brings the total cost of the Bryston to $4395 --
$900 more than the Ai500. I prefer Brystons remote because it fits better in the
hand and is backlit. However, for $400, I would expect a remote control to be something
special. In terms of power, the B100 cant quite match the Stellos 150Wpc
output, instead delivering 100Wpc into 8 ohms, and not quite doubling that into 4 ohms, to
180Wpc. On paper, the Stello is the beefier integrated amplifier, although in practice
power is not an issue for either design. If youre able to drive either into
clipping, then you listen to music at far higher volumes than I do. I wouldnt buy
one over the other based simply on power ratings.
One respect in which the B100 has a clear advantage is
Brystons famous 20-year, transferable warranty. Even if April Music cant go to
that length, for $3495 they should give their customers at least five years of peace of
mind, instead of the two they do offer.
I spent considerable time listening to Great Lake
Swimmers Ongiara, in particular "Backstage with the Modern
Dancers," through both integrateds. Both created very wide soundstages across the
front of my listening room, although the Ai500 was more adept at communicating a tangible
sense of depth. The B100 wasnt bad in this regard, but with the Ai500 it was just
easier to sense toward the back of the stage.
In terms of transparency, both performed exceptionally
well, providing the most see-through sound of any integrateds Ive ever reviewed. As
I switched back and forth between them, the Stello seemed to convey detail with a touch
more ease than the Bryston, but they were so close in this regard that a blind listening
test would be the only way to confirm this observation. I dont anticipate that
anyone will buy one over the other based solely on transparency.
In the bass department, both the Ai500 and B100 sounded
full and weighty, although the impact of the kick drum on the Great Lake Swimmers album
was greater with the Bryston, with a bit more weight that provided a more visceral
experience of the low frequencies spreading into the room. Bryston components have a
reputation for strong bass; as good as the Stello was, it didnt match the Bryston in
In the end, I found I preferred whichever integrated I was
listening to at the time. This was a sure sign that both were performing to a very high
level, and that Id be happy with either taking up residence in my listening rack.
Prospective buyers will need to spend a good bit of time auditioning both before deciding
which is right for them.
Its taken a long time for an integrated amplifier to
come along that Ive enjoyed as much as the Bryston B100 SST, but the Stello Ai500
has finally arrived, and with it, April Music has a clear winner on their hands. Although
its not cheap, I suspect that significantly improving on its performance would
require spending many multiples of its price, and in this sense the Ai500 offers excellent
value. But more than that, the buyer of the Ai500 will be rewarded with an extremely
high-quality, very flexible, and solidly built component that looks great and will give
pride of ownership for years to come. To paraphrase what my friend said about my system,
April Musics Stello Ai500 doesnt just sound good for a two-channel
integrated, it sounds good period. Highly recommended.
. . . Philip Beaudette
|Stello Ai500 Integrated Amplifier
Price: $3495 USD.
Warranty: Two years parts and labor.
894-18 Alpha Bldg, Bangbae-Dong
Seocho-Gu, Seoul 137-829
Phone: (82) 2-3446-5561
Fax: (82) 2-3446-5564