| Onkyo TX-DS989 Version2 Receiver |
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| Friday, 01 November 2002 | |
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Introduction Onkyo
actually produces two separate lines of consumer audio equipment. Like
Panasonic and Technics, Onkyo has an eponymous line and a higher-end
line sold under the Integra name. But this should not give the
impression that the regular Onkyo products are anything less than high
quality – in fact, the TX-DS989, the top of the Onkyo receiver line at
around $3,500, is an excellent component all round.Since the unit was originally reviewed in AudioRevolution in the fall of 2000, the 989 has lived up to its “future-proof” promise, initially with the addition of DTS-ES, Neo 6 and Dolby Pro Logic II decoding in 2001 and now with version 2 firmware and some hardware updates -- which are available to existing owners as well as being provided as standard on new units -- offering THX Ultra2 and DTS96/24 capability. At the heart of the TX-DS989 is a beefy seven-channel power amp offering up to 130 watts RMS per channel, driven by a power supply with a hefty power transformer, which is always a good sign when evaluating a receiver. The unit is THX Ultra2 certified, meeting the stringent THX specs for low distortion, frequency response and other criteria. The unit features 192 kHz, 24-bit D/A converters, which on the face of it is a complete waste of time. Unless you have a very unusual Firewire (IEEE1394) connection from your DVD-Audio player, you won’t ever be giving it higher sample rates than 96Hz (or even 48 kHz a lot of the time) from an external source, as this is the maximum sample rate the majority of manufacturers will give you from the digital outputs of their DVD players – although 96 kHz outs are increasingly common (even my cheap Sampo has it – see review). However, it’s possible that those cool digital-to-analog converters are not such a waste of time: the Onkyo is firmware-upgradeable via a built-in RS232 serial port: there’s no reason why future upgrades shouldn’t provide some nice surprises, such as encrypted high-definition audio to link to a DVD-Audio player, or even upsampling to 192 kHz. Only time will tell, but several possibilities are there. An interesting design feature of the amplifier is included in its “Wide Range Amplifier Technology,” or WRAT, which includes particularly low negative feedback. Negative feedback is a common process for improving the performance of an amplifier – however, if over-used, it can produce problems. Negative feedback compensates for errors in the amplification process by feeding a correction signal back from output to input, and this is all very well if the signal is cyclic, or repetitive, like a sine wave. But unlike a test signal, music generally is not truly cyclic: in particular, transients such as drum beats or note attacks just happen once, and negative feedback essentially causes a distorted transient to be followed by a distorted space. In addition, the back-to-front impedance of the amplifier can be reduced if the feedback loop extends across the whole unit, and this can make the system very sensitive to the acoustic environment. Imagine this: a sound comes out of the speakers and bounces around the room and then gets picked up by the speakers (acting as microphones), is fed back round the feedback loop due to its low impedance and is presented, incorrectly, at the amp input as an error signal in need of correction. Matti Otala at the University of Finland identified this problem in the 1970s, calling called it “Interface Intermodulation Distortion.” Those of us who discovered it in the studio called it “Ricochet Effect.” High levels of overall negative feedback are believed to be one of the main reasons why some tube amps (with low overall negative feedback), now as in the past, can sound better than many early solid state amps (with high levels of overall feedback): this effect can also make a system very sensitive to the quality of loudspeaker cables, and cause an amp to change its sound quite dramatically in response to small changes in room acoustics. But that’s a subject for another time. There are also plenty of A/V features. There is THX Surround EX to add two rear surround channels to permit 7.1 operation, built-in DTS ES, Dolby and Pro Logic II decoding, a 7.1 analog input for SACD or DVD-A players with analog outs, and an up-sampling capability that doubles the sample rate of digital input signals at 44.1 or 48 kHz sampling up to 88.4 or 96 kHz. Done correctly, upsampling can reduce jitter and improve sonic accuracy. In addition, the TX-DS989 has a comprehensive system for handling multi-room/multi-source activity. |
