TAS 194: ATC SIA2-150 Integrated Amplifier

A Sensational Debut

For over thirty years, ATC Loudspeaker Technology has built a sterling reputation for engineering self-amplified or active speaker systems for professional applications—from recording studios and mastering facilities to ritzy music venues like Disney Hall. ATC consumer gear, though less well known, places the same sharp emphasis on tonal realism, dynamic freedom, and bulletproof reliability. Over the years I have owned a couple of ATC passive two-ways, including my current reference SCM20-2, and I can vouch for these attributes. The SIA2-150 is the first integrated amplifier I’ve reviewed from ATC. In all candor, I have to admit that I was especially interested to see how this amp would mate with my SCM20-2s—a passive version of the bi-amplified studio monitor.

The SIA2-150 is a Class AB solid-state design with a considerable amount of toasty Class A bias. It outputs 150Wpc into 8 ohms. The SIA2-150 uses the same gain-reduction and protection circuits ATC packs into its bi- and tri-amped active speakers to prevent amplifier clipping at high output levels—which can damage loudspeaker drivers. It’s also a proudly minimalist amp with only basic input and volume wheels and a “Standby” button bedecking its titanium-anodized aluminum front panel. There are no glowing front-panel displays, tone and balance controls, or—perish the thought—re-namable inputs or iPod accommodations. It’s just the facts, mum. ATC products are like that; they’ve got a job to do. In a concession to contemporary realities however, a basic remote control is standard. I spoke with founder/designer Billy Woodman about the provocative retro-look and he commented, “The visuals were inspired by my fondness for Art Deco industrial design as expressed in the interior design of automobile dashboards of the 30s and the visual appeal of professional electronic gear of the 50s and 60s. I have tried to give the SIA2 a modern interpretation whilst retaining some of that style.”

As an advocate for the revitalized integrated amplifier, I’d been looking forward to taking on the ATC. One thing is certain: There’s nothing passive or Old School about its performance. It’s a paradigm of balance. Across all the conventional sonic criteria that reviewers take into account, from dynamics and speed to tonality and transparency, the SIA2-150 performs without fanfare and is never caught napping. Its sonic signature is an unwavering midrange forthrightness and fluidity. Its neutral to warmer tonal balance allows for the most critical listening, yet doesn’t cross the threshold into the starkly clinical. Musical fundamentals and overtones are expressed like continuous liquid waves of energy. When Shelby Lynne sings “How Can I Be Sure?” [Lost Highway], the energy of her voice is forceful—you can hear it pressurizing the microphone. Upper-mid and lower-treble information is smooth, and biased to the sweeter side of the spectrum. Listening to solo piano I found that treble transparency does reveal a little shading and doesn’t seem as unfettered or open as it could be, but this is far from an attention-grabber.

Bass response is excellent with precise pitch and plenty of slam, although its style is a more diffuse one­—with a larger degree of romantic bloom and warmth. This character was revealed most often with soundboard instruments like acoustic bass or piano or the explosive close-miked guitar of Laurence Juber [LJ Plays the Beatles, Solid Air]. Warren Bernhart’s piano [So Real, DMP] sounded fuller and less contained in the upper bass, even if it doesn’t seem as firecracker-quick off the line. Similarly Edgar Meyer’s stand-up bass [Appalachian Journey, Sony] conveys a more primal mood rather than a purely calculated one, throwing generous resonances onto the soundstage—a presentation that suggested to me more of what a real bass does in a live performance. There’s plenty of headroom macro-dynamically but the SIA2-150 was equally dogged expressing the low-level micro-dynamics and harmonics of the lead acoustic guitar and rhythm section during Elton John’s “Madman Across the Water.” (This is the raw, “original” version that only made it onto the recent SACD reissue of Tumbleweed Connection [Island/Rocket].)