Yamaha DSP-A3090 AV amplifier

Hard on the heels of Yamaha's first venture into Dolby Digital (AC-3), the RX-V2090 A/V receiver and DDP-1 AC-3 decoder, comes its second-generation AC-3 componentry: the DSP-A3090 integrated amplifier with built-in Dolby Digital decoder. I'm pleased to report that the new unit has solved the bass-management problems we found with the earlier combination. Furthermore, the DSP-A3090 contains quite a few added features that extend its versatility and usefulness as the centerpiece of a cutting-edge home-theater system.

The DSP-A3090's Dolby Digital decoder is the feature of greatest interest to home-theater enthusiasts. What is perhaps most unusual about it is that it can decode signals not only from an AC-3 RF output (available on several recent laserdisc players) but also from any AC-3 bitstream signal fed into the unit's s/pdif digital inputs. And the DSP-A3090 provides five optical connectors and one coaxial digital connector, by far the greatest digital-input capability of any component we have tested. This is one amplifier that will not become obsolete as new program sources with AC-3-encoded digital-bitstream outputs are introduced, such as digital satellite decoders and DVD (digital videodisc) players. The amplifier's VCR3 input, in fact, already carries an alternate DVD designation.

After AC-3 decoding, the DSP-A3090's most important feature is its inclusion of multiple digital sound-enhancement modes, which Yamaha calls Digital Sound Field Processing. In the DSP-A3090 these modes fall into two groups. Although there is some overlap between their functions, one group is primarily for surround-sound enhancement of two-channel stereo music, and the other is for enhancement of video-oriented program material, whether stereo, mono, or surround-sound. In these enhancement modes, digital signal processing is used to generate multiple simulated "reflections" from the original signal. The levels, time patterns, and perceived spatial locations of these reflections mimic the sound fields of the specific performance venues being simulated as the reflection signals are fed through all the speakers in a surround system.

The DSP-A3090's twelve main enhancement modes are selected by individual buttons on the supplied programmable remote control or in round-robin fashion by a front-panel button. Each has two sub-modes. For example, the three Concert Hall modes each provide processing that can simulate the acoustics of two different halls. The three soundtrack-oriented modes - Movie Theater 1, Movie Theater 2, and Dolby Surround - also contain two different sub-modes apiece, and these sub-modes operate slightly differently depending on whether the input signal comes from a standard Dolby Surround-encoded source or from a Dolby Digital AC-3-encoded source. The six remaining modes are Church, Rock Concert, Jazz Club, Concert Video 1 and 2, and TV Theater. The first sub-mode of Concert Video 1 is named Classical/Opera; the manual insists that "it reproduces beautiful sound" and that "you will not be tired from long watching of an opera." (Even Wagner's Parsifal?)

Not only do you get twenty-four surround modes to choose from, but all have at least one adjustable parameter and most have several. Among the things you can change are the temporal spacing of the reflections, the length of time before they are generated, how quickly they decay, and their overall level. Use of the parameter controls is crucial for obtaining best results from Digital Sound Field Processing.

Like the RX-V2090 receiver, the new DSP-A3090 amplifier represents Yamaha's most elaborate realization of Sound Field Processing, with seven channels of amplification. In addition to the five speaker outputs, intended for the primary speakers in a home-theater system (front left, center, and right as well as surround left and right), each rated at 80 watts into 8 ohms, the DSP-A3090 contains a pair of 25-watt outputs to drive two "front-effect" speakers for reproducing frontal simulated reflections. These speakers should be placed, as the manual says, "further apart than the main [front left/right] speakers and on either side and a few feet behind and above the main speaker pair." If you don't have two extra speakers for the front-effect outputs, you can mix the front-effect signals into the front left and right outputs. But I don't recommend this option, which involves throwing a rear-panel Front Mix switch from the 7CH to the 5CH position, since the added simulated reflections in the front left/right speakers can greatly disturb the depth and tonal quality of the stereo image. You might want to leave the Front Mix switch in 7CH mode even if you have only five speakers. Experiment.

Various built-in surround-sound "accessories" are also provided in the DSP-A3090. When playing Dolby Digital material, you can separately adjust the level of the low-frequency effects (LFE) signal that is used, as its name implies, to carry high-level low-frequency sound effects. The adjustment range is from 0 to -20 dB in 1-dB steps, plus full LFE muting. You can also adjust the dynamic range during AC-3 playback from its normal setting of Maximum (the full theatrical dynamic range) down through Standard, suitable for relatively low-level listening, to Minimum, for playback at "extremely low" volume levels. Furthermore, with the Standard setting, you can separately adjust high-level compression and low-level boosting.

Two surround-sound accessories apply to all surround-sound processing. Center Delay adjusts a time delay applied to the center-channel signal so that if the center speaker is closer to the main listening position than the main front left/right speakers, its sound will still reach the listener simultaneously. The manual's explanations of the importance of this feature and of its adjustment are inadequate, which is unfortunately true of its explanations of other important features as well. Center Delay adjustment plays a major role in getting the tightest, most accurate, and most stable front image; increase the setting by 1 millisecond for each foot that the center speaker is closer to you than the main pair.

Finally, when it comes to surround-sound accessories, the DSP-A3090 luxuriously provides three (!) types of digital equalizer. One is a five-band graphic equalizer that adjusts sound only in the center channel, with a +/-6-dB range in frequency bands centered at 100 Hz, 300 Hz, 1 kHz, 3 kHz, and 10 kHz. The other two equalizers adjust signals separately to the main front speakers, the front-effect speakers, and the surround speakers. One is a glorified treble control with gains adjustable from +6 dB to -9 dB and "turnover" frequencies from 1 to 12.7 kHz. The other is a nifty single-band parametric equalizer offering a +/-6-dB boost/cut range and center frequency variable from 1 to 12.7 kHz. Adjustments to all these equalizers can be made using the useful on-screen display, or, after some practice, with just the front-panel display (which can also be used to adjust all other settings of the DSP-A3090). Unfortunately, none of the equalizers is usable in plain two-channel stereo operation.

Except for the presence of multiple analog and digital inputs for some components, hookup is straightforward. The rule of thumb here is to connect as many source outputs to amplifier inputs as possible. For example, a laserdisc player with an AC-3 RF output should feed that signal as well as its standard analog stereo signal and the signal from its optical digital output to the DSP-A3090. The amplifier will decide which input to use when you switch to the laserdisc player (this decision can be overridden).

Audio-only connections are provided for a moving-magnet phono cartridge, a CD player, a tuner, and one recorder. A/V connections (including both S-video and composite-video connectors) are provided for a laserdisc player, a set-top Digital Satellite System or cable box, two record/play VCR's, a VCR3/DVD play-only source, and a front-panel video auxiliary source. Speaker connections are via two-way binding posts that accept stripped wires or single banana plugs. There are also pre-out/main-in connections for the three main front channels, separate mono and stereo line-level subwoofer outputs, line-level outputs for the front-effect and surround channels, and three AC convenience outlets, one unswitched.

A flip-down door on the front panel hides the bass, treble, and balance knobs (which I'd leave centered during Dolby Pro Logic decoding), a bass-extension switch, and a standard headphone jack. Minimal controls are also provided here for nonremote operation. The remote is essential for adjusting the DSP parameters and for speaker balancing, which is even more critical than usual in a full seven-speaker setup.

Lab measurements showed the DSP-A3090 to be a topnotch performer. Within our margin of error, its output powers met or exceeded Yamaha's specifications in both stereo and surround-sound modes. Note that while 80 watts per channel may not sound as impressive as 100 watts, it represents a maximum volume level only 1 dB lower. Furthermore, the DSP-A3090 could deliver this maximum power to all five primary channels simultaneously, which might required by Dolby Digital (but not Pro Logic) program material. That's a total of 400 watts being pumped into your home-theater speaker system. Used with speakers providing adequate bass response or, better yet, with a powered subwoofer or two, the DSP-A3090 is capable of generating prodigious amounts of sound, especially with AC-3-encoded soundtracks.

Good old Dolby Pro Logic processing was excellent in lab tests, with very low noise and distortion and unusually high channel-separation figures. Nonetheless, our measurements of AC-3 decoding once again demonstrated the overall superior cleanliness of the Dolby Digital process. And so it proved in listening tests. Despite my daily exposure to AC-3 decoding, I could not get over the system's outstanding improvements in imaging, dynamic range, noise, distortion and frequency response compared with even the best Dolby Pro Logic decoding, which the DSP-A3090 provides as well. (The Dolby Digital frequency-response spans we measured are limited because these signals on the Dolby Labs AC-3 test disc are not well suited to our measurement equipment.)

The only problem I encountered was that the output from a pink-noise test signal swept across the front speakers (Delos "Surround Spectacular," Disc 2, Track 36) increased in the upper bass and lower midrange when it reached the center speaker. I sometimes heard this effect with soundtracks as a slight heaviness on male voices. It may have originated in an interaction between the crossovers provided in the DSP-A3090 and the bass response of the speakers I used, but it was also measurable as a +6-dB mound in response centered at 80 Hz when the front-speaker and subwoofer outputs were added at equal levels in a mixer. I was able to reduce the problem considerably by dialing in a -4-dB correction at 100 Hz with the cen-ter-channel graphic equalizer. Your speakers may not need any correction.

As for Yamaha's trademark Digital Sound Field Processing, it again proved its worth for all manner of music from classical to pop, although acoustic music, as usual, fared better than electronically manipulated productions. The default settings as a rule produced exaggerated effects, and I recommend lowering Room Size, Room Liveness, and Effect Trim with the DSP parameter controls and possibly also reducing the level of the front-effect speakers.

I was far less impressed with Sound Field Processing applied to surround-sound material, particularly soundtracks and especially Dolby Digital soundtracks. After all, the purpose of the multiple channels in such material is so that the producers can record or create a specific acoustic environment, as opposed to two-channel stereo material, which by definition doesn't carry its own surround-sound ambience - hence the effectiveness of DSP with stereo music and its image-blurring echoeyness with multichannel soundtracks. Still, some people might like the effects produced with soundtracks - it can create a sensational showroom demonstration - and with the DSP-A3090 you can create and adjust them (even turn them off!) to your heart's content.

If you've been waiting for the opportunity to jump into the AC-3-en-coded future, Yamaha's extraordinarily versatile and excellent-performing DSP-A3090 is by far the best Dolby Digital integrated component we've tested. Very highly recommended.

Yamaha DSP-A3090 AV amplifier photo