Denon AVR-3600 AV-receiver
To judge from Denon's well-equipped and well-performing AVR-3600 A/V receiver, manufacturers are at last beginning to get the hang of incorporating Dolby Digital (AC-3) decoding into their products. While a few early components have exhibited notable (and easily avoidable) flaws, Denon has done nothing wrong and a great deal very right in this receiver.
The AVR-3600 is second from the top in Denon's receiver line, the top model being a deluxe THX-certified Dolby Digital unit. While the AVR-3600 is not THX-certified, it's a good bet that much of its circuitry is THX-influenced. Certainly the amplifier power ratings hover in the THX region: 90 watts per channel for all five channels in surround mode, 110 watts per channel in two-channel stereo. Equally important, Denon has implemented a good bass-management system consisting of 80-Hz high-pass crossover filters on the receiver's speaker outputs and a matching 80-Hz low-pass filter on its line-level subwoofer output. (Dolby Labs' requirements in this regard are considerably more relaxed than Lucasfilm's.)
The high-power THX heritage, with the resulting need for a large power transformer and large heat sinks, may be the major reason the AVR-3600 is so heavy (over 47 pounds), although the thickness of its outer casing no doubt also contributes substantially to its mass. It is unusually deep, too, which could present a placement problem. Furthermore, to avoid overheating, Denon recommends maintaining about 4 inches of clearance around the top. rear, and sides of the receiver.
Like other high-power A/V receivers, the AVR-3600 provides several digitally processed surround modes in addition to Dolby Digital and Dolby Pro Logic. Its Super Stadium, Rock Arena, Jazz Club, Classic Concert, and Matrix modes all generate delayed artificial "reflections" and feed them out in various timings and levels through all the speakers in a surround-sound system. These reflections can be controlled to some extent in spacing (Room Size) and amplitude (Effect Level) using the remote control and the receiver's on-screen menu system. Your TV screen must therefore be on for these and other adjustments.
In Dolby Digital and Pro Logic modes, a mild high-frequency rolloff can be engaged via the on-screen menu or by pressing the Cinema button on the AVR-3600's front panel. This function is similar in intent to THX's re-equalization processing, which reduces harshness on soundtracks, but its response curve is different. The effect is much like turning the treble control down about halfway. For those Dolby Digital soundtracks that carry the necessary data stream, you can also switch in three degrees of dynamic-range compression, which should help reduce peak sound levels during late-night listening.
The AVR-3600's front-panel styling is conservative and traditional. The central window contains a white fluorescent alphanumeric display that usually indicates the selected surround-sound mode (or normal stereo) and input. This display can be dimmed or shut off altogether using a button on the remote. To its left are small indicators for Dolby Digital operation, digital-input selection, and analog-input overload. The central window also contains a numerical red LED display of volume level, starting from full mute, then jumping to -60 (dB) and running up in approximately 1-dB steps to +18 (dB). This readout, which is always on (bravo!), is necessary because the large, lightly detented volume control rotates continuously.
Directly below the display window is a row of input-selector buttons, one of which selects the rear-panel AC-3 RF input for use with some laserdisc players. The lowest two rows of buttons are used to pick the surround mode, select one of the forty available tuner presets (preset programming must be done with the remote), choose the recording source, and select the source feeding the receiver's line-level multiroom output. The two small knobs are conventional bass and treble controls.
We've seen the AVR-3600's remote control before, as versions of it have been supplied with previous Denon receivers. We can only reiterate here that among conventional programmable remotes it is one of the best. It groups buttons of different shapes, sizes, and colors to vividly differentiate between functions. From a layout standpoint, its only drawback (which for some may not be a drawback at all) is the use of a flip-open door to hide some of the less frequently used controls such as tuner programming, analog-input level setting, and the on-screen menu functions. The remote's principal operational drawback is the round-robin routine required to select surround modes, coupled with the excessively long muting time when you switch between them.
The receiver's rear panel is as conventional looking as the front, with A/V connectors vertically arrayed in several columns. Confusingly, you won't find all the audio jacks for an A/V component right next to its corresponding video connectors, which are equipped with both composite-video and S-video jacks. A/V connections are furnished for two VCR's, a laserdisc player, a cable/satellite decoder, and one auxiliary source. There is one set of video-monitor outputs, with the on-screen display signal superimposed on the composite-video output. The AVR-3600 has audio-only connections for two tape decks (one set labeled DAT), a CD player, and a moving-magnet phono cartridge. Six line-level preamp outputs are available, five corresponding to each of the speaker outputs (three fronts, two surrounds) and one for a subwoofer. The speaker connectors are multiway binding posts.
As befits a Dolby Digital device, the AVR-3600 has three means of receiving Dolby Digital signals: an AC-3 RF jack for the output of certain laserdisc players and both coaxial and optical digital connectors. The coaxial and optical jacks can also accept two-channel digital signals in the S/PDIF format. The manual's instructions for the coaxial and optical connections are confusing. To hook up a laserdisc player, we recommend using either the optical or coaxial input as well as the AC-3 RF and analog laserdisc inputs. That way you'll get sound from every type of laserdisc regardless of audio format. The unused digital jack can be connected to a CD player.
We used the digital-input connectors in some of our lab tests in order to gain direct access to the internal digital-to-analog converters (DAC's), which are employed in most of the receiver's operating modes. We applied to the DAC's our battery of special CD-player DAC tests. The performance of the DAC's - at least of those connected to the front channels, which were the only ones we could get to in this way - was very good, if not state-of-the-art. Excess noise at the 16-bit level was deceptively good because of the negative linearity error measured at -90 dBFS (decibels referred to digital full scale). Otherwise, excess noise was average.
The rest of the lab-test numbers for stereo, Dolby Digital, and Pro Logic operation were also very good. Output power was more than adequate for very loud playback (extremely loud playback if you use a subwoofer), and noise levels were adequately low. As with our other tests of Dolby Digital components, the frequency-response measurements in Dolby Digital mode were limited at the high end by the contents of the only official test disc available from Dolby Labs (which was really not intended for the kind of testing we do). Tuner performance was average for today's A/V receivers.
Our experience with other Dolby Digital components has proved to us that setting up the system correctly is at least as important as good lab-test performance for obtaining good sound. The setup facilities furnished with the AVR-3600 are sufficiently versatile to produce good results with the kinds of home-theater speaker systems we normally review.
For instance, in the speaker-configuration menu, you are allowed to choose between the use of "large" or "small" front left/right and center speakers. Large is for speakers that can reproduce frequencies below 80 Hz "with sufficient volume." Choosing "small" engages a high-pass filter so that frequencies below 80 Hz are sent to the subwoofer, which presumably has the ability to produce "sufficient volume" at the lowest frequencies.
Provided you use both a subwoofer and a separate center speaker, the "safest" settings for these two controls is "small" for both front left/right and center speakers. High-pass filters are always active in the surround-channel signal paths, which is why the measured surround frequency response falls off below 80 Hz in both Dolby Digital and Dolby Pro Logic modes. Depending on the "size" of the front left/right speakers, the surround-channel deep bass will come out of either the front speakers or the subwoofer. Any front-channel filtering is removed when the "Direct" two-channel playback mode is selected. We recommend using only the "Stereo" mode for two-channel playback because your subwoofer balance may be thrown off when the filtering is removed in the Direct mode.
Getting the subwoofer balance right is immensely aided by incorporating the subwoofer output in the speaker-balance test-tone sequence, a THX-like feature that Dolby Labs does not require in Dolby Digital equipment. While a nifty on-screen thermometer-scale display shows channel balances, presumably so that you can set levels by ear, we recommend using an inexpensive sound-level meter for the most accurate results. The Denon manual actually mentions this and even suggests the meter settings you should use for measurement (bravissimo!).
Once we got the AVR-3600 set up in our listening room, which was easier than usual because of the well-thought-out setup features Denon provides, we achieved extremely good results. Dolby Digital performance was as spectacular as always, and Dolby Pro Logic was decoded with unusual clarity, probably because of the digital processor's low noise and distortion compared with typical analog Pro Logic decoding.
None of the auxiliary surround-sound modes added reverberation to the signal, just ambience reflections. But in some modes these reflections could extend through a rather long interval (more than a second). The resulting sound quality, as usual, varied with the program material and with the ambience adjustments. The main problem with these modes is that the added reflections are identical on each side (left/right), although they are different for the front and surround speakers. In some setups this could produce an annoying in-the-head "mono" image for the surround-speak-er reflections. I did like the AVR-3600's "party" mode (unimaginatively called 5CH-Stereo), which sends signals without added ambience reflections to all five speaker outputs, and also the equally useful Matrix mode, which sends a single reflection to the surround channels. I also admire Denon's bravery in not including specifically labeled ambience-enhancement modes for soundtrack playback. These generally do more harm than good by screwing up dialogue intelligibility.
Such knowing restraint is perhaps the hallmark of the AVR-3600, which in its quietly conservative and competent way is one of the best receivers containing Dolby Digital processing that we've tested.
