Marantz AV600 AV-receiver

The AV600 A/V tuner/preamplifier is Marantz's second Home THX component, following the compact and versatile MA500 singlechannel power amp. Besides full Home THX enhancement of Dolby Pro Logic processing, an AM/FM tuner, and considerable A/V switching capability, the AV600 has a few features that set it apart in usability and convenience from other Home THX controllers we have tested.

The AV600's most unusual feature is its provision of two subwoofer outputs, selectable via a rear-panel switch to operate in monaural (parallel) or stereo. Although the actual usefulness of stereo subwoofers - particularly those operating only below 80 Hz, as they do in Home THX systems - is still controversial, the AV600 at least will let you decide for yourself. Separate low-pass filtering is provided for each subwoofer output, and 80-Hz high-pass filtering is switched into all channels when the subwoofer outputs are turned on.

Also unusual is the front-panel input-level control, which operates in conjunction with a set of flashing indicator lights. This knob, located along with quite a few other controls behind a front-panel fold-down door, is best considered an input-overload prevention knob. You adjust it so that a red peak-indicator light "only flashes briefly during the very loudest passages." This adjustment helps insure that the peak outputs of your signal source are not overloading the Dolby Pro Logic decoder chip. There has been a de facto standard output level from home CD and laserdisc players for quite some time, however, so when you're playing the digital soundtracks of a laserdisc or using a home CD player you should not have to turn the input-level control more than a couple of "dots" away from its center detent to get the indicators to light up properly. If you do, there is something amiss with the player's output level or its connection to the AV600.

Marantz hasn't forgotten the "standard" A/V tuner/preamp features either. For example, you can separately select audio and video sources to get the FM-tuner audio to go along with broadcast video for that rare stereo simulcast. You can also select the source to be recorded on any attached audio or video deck independently of what is being heard or watched. The tuner comes with more preset memories than you'll probably ever need: thirty, distributable in any fashion over the AM and FM bands.

Besides Home THX processing, several other surround-sound modes are provided. These include straight Dolby Pro Logic, Movie (which allows a very long surround-channel delay time), and Hall and Matrix (for music enhancement). A mono mode feeds everything through the center speaker. The processing mode is selected with a front-panel button that's duplicated on the remote control.

Convenience features include bass and treble controls and a front-panel quarter-inch headphone jack. The front panel also has buttons for activating the useful on-screen display, for turning off the even more useful front-panel fluorescent display, and for setting the preamp's sleep timer, which will also turn off whatever's plugged into the two switched rear-panel AC outlets. The AV600's mute control is available on both the front panel and the remote, which is vastly more convenient than just on the remote. The handset itself has lots of non-AV600 buttons suitable for programming with the commands used by other infrared handsets. It also has a full complement of speaker-balancing controls, including a test signal that, for once, is manually switched between speakers - and switches without interruption or muting. You're also free to alter the speaker balances, including the levels of any subwoofers, separately for the soundtrack modes (THX, Dolby Pro Logic, Movie) and the others (Hall, Matrix, Monaural). The only typical feature lacking in the AV600 is a phono-preamp section, which you probably won't miss.

Connections and switching are provided for eight external sources, three audio only (CD, tape, DCC) and five audio/video with both composite- and S-video connectors (TV, laserdisc, two VCR's, and aux). The auxiliary input is located behind the front-panel door.

Several outputs are available. First, there's the video-monitor output, either composite or S-video. Next there's a line output that feeds out a duplicate of the selected input. Then there are the main preamp outputs, eight phono jacks: a pair each for left and right front, center (in parallel), left and right surround, and left and right subwoofer. A 25-pin D-connector is available for feeding these outputs to a similarly equipped multichannel Home THX power amplifier via a single multiconductor cable. Additional rear-panel connections include one for a remote-control relay that hooks up to other Marantz equipment, a screw-on F-connector FM antenna terminal, and thumbscrew connections for an AM antenna. Back-panel switches that must be properly set during initial setup, or possibly if you change speakers, control the subwoofer status (none, mono, or stereo) and the center-channel bandwidth - "none" (corresponding to the Phantom mode in the more usual Pro Logic nomenclature), "large/ THX" (corresponding to Wide, delivering the same bandwidth to all three front speakers), and "small" (corresponding to Normal, splitting low frequencies in the center channel out to the front left and right outputs).

The AV600 performed very well on the test bench, with good to excellent performance in most areas. Among the best figures were the high stereo FM sensitivity, the low noise in stereo operation, and the low distortion in Pro Logic operation. Only a bit less superb were frequency response, which tended to drop off slightly at the extremes of the frequency range, and surround-channel noise level, which was slightly higher than the best we have measured from an analog Pro Logic decoder. Surround-channel frequency-response tracking was very good, with very small, and essentially inaudible, errors over the 40-dB range of the test. Tone-control curves were typical. The front-panel peak-indicator light came on with an input about 2 dB below the standard maximum CD/laserdisc-play-er output level of 2 volts, which is a sensible threshold level.

The Pro Logic surround-calibration error was zero (within our measure-ment-error range) for Home THX operation, but it was larger for plain Dolby Pro Logic processing, which uses a different reference level. Although not the main reason for its inclusion, the front-panel input-level control can be used to zero-out errors for either mode if you have the necessary measurement equipment. Then again, Dolby Labs believes that results on this test aren't particularly critical, which is a reasonable judgment, at least for the amount of error encountered here. The Home THX surround-channel "timbre matching" equalization error was not measurable because of the THX decorrelation processing, which was applied to both channels.

In listening tests, the AV600's Home THX surround-decorrelation processing added an average amount of "swimminess" or tunnel-like quality to the surround outputs relative to other Home THX processors we have used. This artifact tends to be noticeable mainly with test tones, however, and not so much on most soundtracks.

Otherwise, the AV600 worked just about as well as those other THX units, which is to say very well indeed. Sound steering in straight Pro Logic or Home THX operation was precise, and the corresponding noise levels were low except for the always problematic surround-channel noise, which hovered just at the threshold of audibility. The two music-processing modes were rather gentle in their application of ambience enhancement - better too little than too much here - although you might want to turn down the surround speakers a bit when using them. I preferred the Matrix mode to the Hall because it seemed to produce less of a change in the front-channel sound quality. Both are usable with a wide variety of music.

The remote handled well despite the uniformity of the buttons and the monotony of their layout. The high-visibility labeling helped greatly.

Like most A/V components, the AV600 has its share of minor ergonomic problems. For instance, there's the round-robin surround-mode selection, which prevents the sort of A/B comparison between modes that is essential for quick selection of the one that's best for the program material. I also found the steps of the individual channel-level adjustments slightly too coarse for really precise level matching, though the AV600's 1-dB increments are far better than the 2-dB steps found on some non-THX equipment. The tuner's automatic presetting function was overzealous in its operation in New York City's extremely crowded FM band, assigning "phantom" stations (frequencies in between real stations) to memory. Manual presetting with the remote control was much more satisfactory.

Finally, having gone to the trouble of providing the connections and circuitry for stereo subwoofer outputs, Marantz has practically negated their usefulness by neglecting to supply those outputs with the amenities they require for proper setup. Specifically, even when set to stereo subwoofer operation, the built-in channel-balance test signal plays through both subwoofer outputs simultaneously, the channel-selection and channel-level controls operate on both subwoofer outputs simultaneously, and there is no balance control enabling you to activate one subwoofer channel or the other when using an external test tone, from a test CD, for example.

Stereo subwoofers are, by definition, not going to be located in the same place. Because room acoustics will influence the output of each subwoofer differently, they are thus unlikely to require the same level setting for proper blending with the main speakers. Even if your subwoofer amplifier has its own level control, you need a way of determining how to set it. In the absence of cooperation from the test-signal generator, you have to disconnect the main and subwoofer outputs for one channel while balancing the other, an operation further complicated by the fixed round-robin sequencing of the channel-selection button.

All these concerns, however, will be important only to those drawn to the AV600 because of its stereo subwoofer outputs. Most people will probably have only one subwoofer and will set the subwoofer-output switch to mono operation, which works just fine and avoids a long series of disconnections and reconnections during setup.

Far more important is the gain in "theatricality" afforded by the Marantz AV600's Home THX processing. The surround-channel decorrelation prevents the in-the-head imaging effects that can be distracting with plain Dolby Pro Logic decoding and increases the sense of sonic envelopment by the surround speakers, whether Home THX-type dipoles or not. Home THX re-equalization, which introduces a specifically shaped high-frequency response, helps greatly to reduce harshness on soundtracks - all soundtracks, not just those on THX laserdiscs - especially when they are played loud, which the sound quality of the unit encourages. As if that weren't enough, Marantz is offering free to all AV600 purchasers a copy of Lucasfilm's own Home THX demonstration laserdisc (appropriately nicknamed the "Wow!" disc, after the title of its first track), a program infinitely more persuasive than any product review can be regarding the virtues of the processing offered by this tuner/preamplifier.

Marantz AV600 AV-receiver photo