The Short Form

Price $1,400 / audioplusservices.com / 800-663-9352

Snapshot

Though this receiver is short on the latest features, its elegant simplicity conceals top-flight audio performance.

Plus

•Outstanding sound and power •3 HDMI inputs •Simple operation and elegant looks

Minus

•No video-scaling or one-cable HDMI option •A few crossover/delay setup restrictions •A-BUS only for multiroom audio - no RCA outputs

Key Features

•6-source/6-zone system •Expandable to 30 listening zones •60-watt per channel amplifier •Four different control options •Modular, card-based architecture •XM, Sirius, AM/FM, or all three •iPod integration •GXR2: 17.4 x 5.8 x 18 in; 54 lb

Test Bench

The 640R consistently delivered expected behavior and declined to snap fuses, smoke circuit boards, or require resetting, despite the usual abuse. Its stereo power could almost sneak by on a "150 watts x 2" model, and it did indeed deliver in excess of its full rated power with five channels driven - and very nearly with seven. It also set new receiver benchmarks for PCM-stereo (and Dolby) linearity at -90 dB (perfect!), real-world S/N ratio, and "excess noise." Full Lab Results

SETUP Hooking up the 640R was straightforward. Nice color-coded speaker outputs, a dedicated coax and optical digital-audio input for every component, and basic but logical onscreen displays. Menu response using the handsome, billet-aluminum remote was a little jumpy, but the process was easy.

I encountered a few oddities, such as the receiver's inability to set different delays between left and right front or surround speakers or to set center or surround-back distances greater than the for fronts or surrounds, but these won't trouble most setups. Only a single crossover frequency is assignable for all speakers; it forbids "large" center with "small" L/R, but it's otherwise very flexible, being adjustable by 10-Hz increments from 40 to 150 Hz, plus 200 Hz. The 640R's dual-zone multiroom function is also unusual, in that it lacks the traditional RCA or speaker outputs for the secondary zones and instead uses Cambridge's Incognito connectivity, a version of the A-BUS system that sends audio and composite video via RJ-45 cabling to in-wall keypad/amplifiers in your remote rooms.

MUSIC AND MOVIES As I expected, straight-through video remained pristine through the 640R. While (as noted) the receiver doesn't upscale any signals, it does cross-convert from the S-video or composite inputs to the component-video output (not to HDMI). But image quality suffers noticeably, so it'd be best to make both S-video and component connections to the monitor if you regularly use any S-video sources. Both HDMI and component signals looked perfectly unaffected by their journeys through the Cambridge receiver.

I was not surprised that audio quality was of the same high order. This is a very fine-performing audio component, with ample, pristine power and outstanding surround decoding and processing. Stereo listening via moderate-sensitivity, high-end compact monitors yielded honestly high-end results (at least, from audiophile-grade recordings), with the clarity, transient precision, and textural transparency I expect of a top-flight system.

I confirmed the excellence of the 640R's amplifier with a handful of favorite multichannel DVD-Audio and SACD recordings, among them a newly discovered Naxos album of little-known "theater music" from 20th-century Russian composer Dmitri Shostakovich. This proved a delightful surprise both sonically (outstanding clarity and simple, un-hyped surround perspective) and musically (who ever dreamed Shostakovich wrote an entrance for slide guitar? Not I!). I was rewarded with the striking clarity of timbre on solo instruments and the defined, three-dimensional texture of massed strings and woodwinds that only fully transparent playback offers.