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Positioned
between the DSP circuitry and the power amplifier stage, the High Performance
Digital Circuitry makes a large contribution to the DSP-AZ1’s
outstanding audio performance. It exemplifies the Digital ToP-ART concept
of maximizing the quality of the digital circuitry while minimizing
analog circuitry, and also adheres to the ToP-ART philosophy of logical,
straight-line circuit layout for optimum signal purity. Yamaha’s
superior LSI technology as well as our long experience in designing
both home and professional audio circuit boards are responsible for
the high performance and reliability of this circuit. It is composed
of a DAC block, a volume control block and the Processor Direct circuitry.
Superior
Digital-to-Analog Converter System
For the important digital-to-analog converters, Yamaha has chosen the
PCM1704 manufactured by the high-end audio expert, Burr-Brown. The DSP-AZ1
uses 10 of these DACs, for the eight main channels and the two subwoofer
outputs. The PCM1704 is a high-performance, precision 24-bit BiCMOS
Sign-Magnitude DAC with ultra-low distortion of only 0.0008% (K-grade
THD + N) and S/N ratio of 120dB. It offers superior low level linearity,
with excellent full-scale performance under varying operating conditions.
Its major benefit is performing accurate sound field reproduction for
high quality multi-channel reproduction such as Dolby Digital and DTS.
For two-channel stereo, the PCM1704 provides outstanding separation
and accurate musical delineation. An additional advantage is its 192kHz/24-bit
conversion capability, making it compatible with the latest (and future)
high resolution digital audio sources.
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Digitally
Regulated Volume Control
Digital volume controls have become popular in home audio products, but
for various reasons, analog is the better choice for this key component.
Yamaha has combined the best of both by designing a high precision digital
device (Crystal Semiconductor CS3310 LSIs) that controls an analog signal.
This provides two benefits. First, a digitally controlled device is more
accurate for balancing levels between channels and offers much finer control
than an analog device. In the DSP-AZ1, the control range is from 0dB to
-99dB in extremely accurate 0.5dB steps throughout the entire range, with
negligible gang error. This wide range and narrow steps mean that greater
attenuation is possible, with precision even at low volume levels. Second,
an analog volume control permits good signal resolution of very low signal
levels. This is important for subtle signals that are often masked by
louder signals and are not resolved as clearly.
The DSP-AZ1 also features an improved rotary knob axis that provides a
superior tactile sensation as the knob is turned. Finally, the selected
volume level and a bar graph display are both shown on the front panel
display and the on-screen display. Processor
Direct Switch
The DSP-AZ1 has a Processor Direct Switch that when engaged, provides
a direct signal connection between the processor board and the power
amplifier section. As a result, the regulated digital volume device
avoids the wiring on the circuit board, thus bypassing all control circuits.
This shortens the signal path, feeding the pure, robust signal directly
to the eight amplification channels for cleaner, more efficient operation
and higher quality sound.
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