Stello Ai500 imponerar!

[Transient Design]

Efter ett bra test på 6Moons av Stello Ai500 så kom nu också reaktionen i form av en Blue Moon Award till både Ai500 och CD500!

De går så långt som att kalla Stello Ai500 för "Super Integrated Amplifier".

Citat:

"On features and appearance, the Korean also trumps the boxy Krell S-300i and Metronome's MT One. Meanwhile the coaxial digital input becomes the cat's meow to upgrade an aging CD player without having to reinvest in a dying category. In short, Bryston, Hegel, Krell, simaudio et al must now account for April Music. The Koreans have raised the bar in this sector on functionality and luxury without shortchanging performance."

Sedan finns nu också ett test av Stello Ai500 i The Absolute Sound nr 4! Se nedan:

Edited March 15, 2010 by Transient Design

[Transient Design]

Test av Stello Ai500 i The Absolute Sound nr 4:

In the past I've rarely used integrated amplifiers because they create a location conundrum I haven't been able to solve. In an average-sized room you have to choose whether to have a long run of speaker cable from your integrated amplifier to your speakers or place all your gear close to (or behind) your speakers so you can use shorter speaker cables. The first option can be inconvenient and expensive (to the point of negating any savings over separates). The second option puts your front-end gear in a less than acoustically benign environment, next to the very objects that cause physical and acoustic resonances. In most rooms integrated amplifiers don't float my boat. It wasn't until I set up my first desktop system that I had a listening environment that fully exploited an integrated amplifier's virtues. In a nearfield system all the components are within three feet of each other so short cable runs are a given. Combining two boxes (preamplifier and power amplifier) or even three boxes (dlgtal-to-analog converter, preamplifier, and power amplifier) in one box makes perfect ergonomic sense. How did I come to this startling realization? The April Music Stello A500 helped me see the light.

Korean audio distributor Simon Lee created April Music in 1998 after he decided that the brands he imported had become too expensive for his customers to afford. His goal was and is simple -make components that preserve what he calls "the nature of music." To achieve this end Lee uses Korean manufacturing facilities and top-echelon international product designers such as Britain's Kenneth Grange. As a founding partner in the interdisciplinary design firm Pentagram, Grange has worked for B&W, Kodak, and the Parker Pen Company. Grange's design philosophy can be summed up by the simple phrase "a well designed object should be a pleasure to use." Although some of April Music's original products were rather prosaic black boxes, such as the Stello DA 100, the current Aura line and the Ai500 have a visual flair and elegance not often found in audio devices, regardless of price. The Ai500 sports elegantly curved sides and a bold yet simple front faceplate. There's a single large circular volume knob on the right side of the front, a compact oval LED display in the center above a row of source-selector buttons, and a small on/off button on the left with a small white LED. The overall look is clean, modern, and unintimidating, even to a neophyte.

The Ai500's remote control continues this clean modern aesthetic. Its solid-feeling aluminum casing features the same satin finish, oval shape, and symmetrical button layout as the Ai500 itself. The remote was designed to also control the companion model Stello CDA500 CD player, so only the bottom twelve of its thirty-two buttons are functional with the Ai500. Its weight and size make it hard to misplace and also make it an excellent defensive weapon for close hand-to-hand fighting.

While the front panel of the Ai500 may be Spartan, the wellpopulated rear panel includes a complete and well-thought-out set of inputs and outputs. One balanced XLR input joins five unbalanced RCA analog inputs along with S/PDIF, TosLink, and USB digtal inputs. The Ai500 has separately marked iPod analog and USB inputs. This USB "input" did not do anything on my review unit, not even supply power to the iPod, so I can only surmise it was broken or not yet fully implemented, but the analog input worked fine. The Ai500 has only one pair of speaker outputs. If you require sound in a second zone or room, the A1500 does have a pair of single-ended variable RCA linelevel outputs as well as a pair of single-ended RCA fixed-level outputs. I used the variable-level outputs for a subwoofer, but a second power amp could just as easily be attached to them.

Unlike many contemporary power amplifier designs, which have migrated to ICE or other Class D switching amplifiers, the A500 is a more traditional Class AB circuit based around Hitachi MOSFET output devices, coupled to a large 800VA toroidal transformer and 90,000uF capacitor banks. The Ai500 delivers 150Wpc into eight ohms and doubles its output to 30OWpc at four ohms. Even at idle the Ai500 generates a certain amount of heat and needs some space around it for proper ventilation. It gets warm enough to make me suspect that it actually runs in Class A mode for the first five or ten watts of its output. Under my desktop the A500 was a welcome heat-augmentation device during cold winter months, but, come June, the Ai500S thermal contribution to my desktop environment will be less well received.

The Ai500's dual-differential Class A preamp has 35dB of gain. It utilizes a Cirrus Logic CS3310 volume-controller chip coupled to a precision stepped-resistor array for level attenuation. If you have a source with its own bullt-in preamp, you can easily convert the Ai500 into a basic power amplifier by attaching a pair of single-ended RCA connections from your variable output source to the "Bypass" inputs on the back of the amplifier and then choosing "Bypass" as your input on the remote. This bypass input can also be used in conjunction with an AV pre/pro to rout its signals through the Ai500.

Setting up the Stello Ai500 in my desktop system was easy. In addition to one pair of speakers, I attached inputs from the USB output from my computer, the S/PDIF connection from the Empirical Audio Off-Ramp 3, and a balanced analog signal from a Weiss Minerva D/A. I wished the Ai500 had an AES/ EBU digital input, but since it doesn't, occasionally during the review I had to remove the Empirical Audio's digital connection so I could attach my CEC TL-2 CD transport via its S/PDIF outputs. Once it was installed, I let the A500 burn in for a couple of days before I began serious listening. My initial impressions of

the Stello's sound were all positive. This is one very quiet piece of electronics. It generates no physical or electronic hum and very low levels of hiss from the tweeter. In this respect the Ai500 was superior to the Adam A5 active speakers I reviewed recently. The Adams had noticeably higher levels of hiss from their tweeters. Probably 99% of Ai500 users will use the Ai500 as an integrated

amplifier, not as a basic power amplifier. But since it has provisions to be used as a power amplifier, I used it this way for some of my listening, connected directly to the unbalanced RCA outputs of the Weiss Minerva Firewire DMZ. Using the Weiss also made it possible to listen to 192/24 digital files in their native mode. As a power amplifier the Ai500 was impressive, easily matching the overall performance of both my Accuphase P-300 and Edge Electronics AV-6 power amplifiers. In some sonic parameters I preferred the Ai500 to both of these other amplifiers. The Ai500S rendition of spatial information and focus bordered on the supernatural. The Ai500S ability to control speakers with complex crossovers, such as the new Joseph Audo Pulsars, was exemplary. Also the Ai500 ranks among the least grainy solidstate amplifiers I've heard. Grain? It's not even talcum-powdersized. In this respect the Ai500 power amp section even matched my reference Pass X150. Complex musical textures, such as the accordion, fiddles, electric guitars, and percussion parts on the Woody Guthrie song "Pastures of Plenty" from the live JhLas Reunion CD retained all their textural individuality. Many systems, including the recently reviewed Adam A5 system, homogenized many of these subtle detds. A couple of years ago Sean Watkins, one of the founding members of the acoustic super-group Nickel Creek, released the solo album 26 MiLes. It includes the instrumental "Chutes and Ladders," a fast, harmonically rich, and dynamically complex piece that requires a system that can stop and start on a dime. The electric bass can't be sludgy or heavy, or many of the music's micro and macro-dynamic subtleties are lost. The Ai500's power amplifier section mated with the Joseph Audio Pulsars revealed all of "Chutes and Ladders" musical micro-details with ease. [i

heard the Ai500 at the most recent CES driving, of all things, a pair of Magneplanar 20.Is. I was shocked by the Ai500's authorig and dynamics with this notorious difficult load, along with the Ai500's overall musicality. ]

Why Not Stello Ai500?

Obviously, most people who buy an Ai500 will use it as an integrated amplifier and probably want to use its USB and

S/PDIF digtal inputs, so I spent a good deal of my reviewing time evaluating these inputs. Sonically the Ai5003 USB input

ranks somewhere between the High Resolution Technologies Musicstreamer+ and the Empirical Audio Overdrive DAC. The

Ai500's USB circuits have slightly better depth recreation than the Musicstreamer+, as well as superior dimensionality and lateral

focus. But the Empirical Audio Overdrive DAC surpassed the A500 in every meaningful sonic parameter. Given the Overdrive's

price and highly focused feature set, this isn't surprising. Since I've been using the Amarra software package on

my computer, I've spent a good bit of time conducting what I've come to refer to as "The Amarra Test." This consists of

turning the Amarra software program on and off while music is playing to see if I can detect a difference. With some DACs,

such as the older Stello DA-100 or High Resolution technologies Musicstreamer, I can't detect any changes between 'Amarra on"

and "Amarra off." With others, such as the Weiss Minerva or the Empirical Audio Overdrive DAC, the differences are quite

noticeable. The Ai500S USB input is sufficiently revealing that I could hear some changes between "Amarra on" and "Amarra

off." With Amarra turned on, the overall image had greater three-dmensionality and lateral focus as well as a more cohesive

dynamic character. The coaxial S/PDIF input on the Ai500 can deliver especially good sonics; it all depends on what it's hooked

up to. The combination of the Empirical Audio Off-Ramp 3, which converted USB to S/PDIF, and the A500 coaxial input was on

a par with the Weiss Minerva on Red Book digital files. The Off-Ramp 3/Ai500 combo reminded me of the Off-Ramp 3/ Overdrive

in dynamics, dimensionality, and musicality. Compared with the Weiss, the Off-Ramp/Ai500 combo is a hair more musical, but

also ever so slightly less detailed.

On analog sources, such as the Weiss Minerva's analog outputs the Ai500 can deliver h i g h l y musical and detailed sound. The Ai500's analog preamp's transparency is almost as good as my Reference Line passive preamp. On my own 192/24 recording of the Boulder Philharmonic, the Reference line seemed to create a slightly more spacious soundstage, especially when it came to delineating the rear-wall reflecdons behind the orchestra, but the A500 generated a bit more dynamic contrast. The horn sections in my recent recording of Berlioz's Symphonie Fantastique had more dynamic energy through the Ai500. Just prior to installing the Stello Ai500 in my system I'd been using Peachtree Audio's Nova integrated DAC/preamp/ amplifier. Thts $1295 tube-output integrated amplifier has similar input capabilities (actually the Nova has two coaxial digital S/PDIF and TosLink inputs to the AI500S one), and also works beautifully in a desktop system. While the Nova is highly musical, its power amplifier section lacks the Ai500's

ability to control a speaker's drivers as precisely The Joseph Audio Pulsar's bass and dynamics were substantially better when driven by the Ai500 than by the Nova. In comparison the Nova had a tendency to homogenize micro-dynamics, compress macro-dynamics, and slightly smear textural details, while the Ai500 delivered everything with uncanny ease. I'm sure many audiophiles looking for an integrated amplifier would like to know how the Ai500 stacks up against the current offerings from Krell and Simaudio, but since I haven't heard these units I can't give you the scoop. However, what I have heard from the Ai500 leads me to surmise that any other integrated amplifier would be hard-pressed to surpass its sonic capabilities. For $3495 the April Music Stello Ai500 is a killer product at an attractive price.

I'm Now an lnteqrated Convert

At the beginning of this review I revealed my biases against integrated amplifiers in room-based systems. Those concerns haven't changed. But after living with the Stello A500 for several months in my desktop system, I have been thoroughly converted-integrated amps rule for desktop use, and the Ai500 is one heck of a good integrated amplifier. For most music lovers the April Music Stello Ai500 can deliver a completely satisfying one-box solution for a highend nearfield desktop system. But for audiophiles who require the ultimate in resolution from their digital music files, the Ai500 needs to be mated with a topechelon USB signal-converter or DAC, or a Firewire DAC, such as the Empirical Audio Off-Ramp 3, Empirical Overdrive DAC, or Weiss Minerva DAC. Finally I would be remiss if I did not direct your attention once more to the Stello Ai500's overall fit, finish, and visual style. Unlike most mid-priced audiophile gear, which tends to be either stylishloohng or stylish-sounding, the Stello Ai500 succeeds at being both.

Edited March 15, 2010 by Transient Design