wide, so those of you interested in purchas- ing should be sure that your equipment rack can handle its 18 5/16-inch depth.
The back panel is somewhat sparsely appointed in terms of digital connectivity. I feel that the number of digital inputs should be larger than provided for a component at this price level, since our systems are intro- ducing more digital sources as time march- es forward. Provided are two TOSLink opti- cal inputs, with default assignments of TV/Sat and CD-R/Tape 1. Two S/PDIF coaxi- al digital inputs are on the back panel, with default assignments of DVD/LD and CD also available. Should you be blessed with a mismatch, a converter will need to be employed. Upping both digital input con- nectors to three of each would likely handle most end-user environments where the VSX-56TXi is used.
Analog-only inputs for line-level audio sources are also a bit shy but not to the point of being troubling. Three stereo ana- log audio-only inputs are provided for CD-R, MD/Tape and CD. In addition, those with LP playback capability will be pleased to find an MM-capable phono stage, with ground- ing also provided. There are four A/V inputs provided and each has stereo audio, com- posite, and S-video connectivity. A pair of assignable component video inputs is also available. A single set of multichannel analog inputs (7.1) are also included so that a single multichannel disc player can be connected via analog input. In addition, a pair of assign- able component video inputs are available.
Analog tape loops are well accounted for with a pair of audio only outputs avail- able. In addition, two video tape loops, with stereo audio, composite, and S-video are provided. A pair of digital audio out- puts via TOSLink are also included with the VSX-56TXi
The VSX-56TXi carries the final “i” in the model designation to indicate i.Link capabil- ity. i.Link (FireWire, IEEE 1394) is a specific implementation of FireWire 1394a, which allows for the uncompressed encrypted transfer of audio streams, including high- resolution DVD-Audio and SA-CD in their native forms. Assuming you have an appro- priately equipped player, a single cable can be used for the transfer of all audio instead of multiple cables. In addition, a USB Audio input, capable of accepting MP3, Windows Media Audio, and uncompressed PCM is also available.
i.Link was a bit troublesome in its opera- tion, and I need to take a few moments out to tell you what the limitations are. When setting up the VSX-56TXi there is a menu option for SA-CD setup, which contains a parameter for SA-CD direct mode. With SA- CD direct mode off, all SA-CD material will
be played back as stereo only, but you gain the ability to use MCACC and bass man- agement when not played back in direct mode. This is even true when playing back the multichannel tracks on surround SA- CDs. With SA-CD direct mode on, you can listen to surround SA-CD tracks, but you lose MCACC. DVD-Audio functions a little bit cleaner, likely due to the ability to direct- ly process the PCM data. MCACC and bass management were available with 24-bit/96 kHz stereo and surround discs and 24- bit/192 kHz stereo discs. For DVD-Audio at 24-bit/48 kHz and 24-bit/96 kHz, all DSP functions were available, however, at 24- bit/192 kHz stereo discs only bass manage- ment was available. This would indicate that DSP horsepower is a limiting factor. Operating on 24-bit/192 kHz data requires four times the DSP horsepower; you have twice the samples to work with and half the time-window for the operations.
The binding posts on the VSX-56TXi are decent, though not outstanding. While it is possible to use bare wire or spade lugs, given the tight spacing of the posts the best candidate is the “good old” banana plug. This isn't a problem for me, as all my loud- speaker cables terminate with banana plugs. The spacing between plus and minus posts is at 1 inch, so attached dual banana plugs generally won't work. Once connected, the banana plugs were gripped tightly, and I never had issues with the con- nectors detaching accidentally.
Digital Topology
Receivers and preamp/processors are brought to audio life by their digital stages. There are a variety of solutions available, and some of the process is in selecting the appropriate components to achieve the intended sonic goals, while not exceeding the overall sonic goal of the product. Digital to analog convertors are the last piece of the puzzle, and they are responsible for tak- ing the output of Digital Signal Processors to convert the signal to an analog voltage, which is used to drive a power amplifier stage. In the case of the VSX-56TXi, there are four stereo DACs employed. For the first six channels (Front L/C/R, Subwoofer, Side L/R) the Asahi Kasei Microsystems AK4383 is used. The AK4383 is a maximum 8x over- sampling Delta-Sigma Modulation DAC capable of decoding PCM input up to 24- bit/192 kHz, as well as natively decoding DSD (from SA-CD). Performance specs on the AK4383 indicate a THD+N of -94 dB, with a signal-to-noise ratio (S/N) of 110 dB. This approximates 19-bit performance. While not quite state-of-the-art for DAC per- formance, the VSX-56TXi isn't priced in the
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state-of-the-art category either. The back surround channels (used only for DTS®-ES [Matrix and Discrete], DTS: Neo6, Dolby® ProLogic® IIx, and Dolby Digital Surround EX™) are handled capably by the AK4382A, which has comparable specifica- tions to the part used for the main channels, but lacks DSD support, which is not neces- sary at present.
Digital Signal Processing is accom- plished by a pair of Freescale (Motorola) 56367 DSP chips. The DSP56367 is a com- mon part and is used by many in the indus- try. In this case, the first DSP56367 is used for traditional DSP functionality (lossy format decoding, matrix decoding, proprietary DSP fields, time alignment, bass management). The second DSP is used exclusively for MCACC, to implement the equalization system.
It is possible to apply DSP to analog inputs, and analog to digital conversion is provided by the Asahi Kasei Microsystems AK5380 ADC. The AK5380 is a stereo delta- sigma modulator ADC, with output sampling up to 24-bit/96 kHz with an S/N ratio of 106 dB and the ability to operate cleanly, even in relatively high temperature environments approaching 200 F. By sampling at 24- bit/96 kHz, this allows for high fidelity to the analog input prior to DSP application.
