Sony STR-DA2ES ES Receivers Technical Background

ES Receivers 2002

Technical Background

Version 3.0; July 29, 200 2

Introduction

From the very beginning, ES receivers have benefited from Sony's
comprehensive expertise in digital source components and Sony's thorough
understanding of digital signals. Those insights led directly to significant Sony
ES innovations:

• The world's first outboard D/A converter (DAS-702E S , 198 5) .

• The world's first Dolby® Surround decoder to operate in the digital domain

(SDP-505ES, 1986).

• The world's first all-digital preamplifier (TA-E1000ESD, 1989).

• 24-bit Dolby Digital® decoding (SDP-EP9ES, 1997).

• Digital Cinema Sound™ processing (STR-DA90ESG, 199 7) .

• World's first floating-point 32-bit preamplifier (TA-E900 0ES , 1998).

The ES receiver line—all new for 2002—is a worthy successor to these
landmark components. The STR-DA7ES, DA4ES and DA2ES offer a host of
new advantages:

• Seven separate channels of amplification (STR-DA7ES, DA4ES)

• Better "downmixi ng "

• More precise control over volume

• Higher-accuracy digital decoding and processing

• Full compatibility with the latest surround sound formats, including Dolby

Digital® EX, Dolby® Pro Logic® II -movie, Pro Logic II-music, dts® ES
discrete 6.1, dts ES matri x 6.1, dts 96/ 24, Ne o6:cinema and Neo6:music.

• Better time-base accuracy

• Better analog direct fa ci l i ti es

These new ES receivers are worthy of the most sophisticated home
theaters and ready for the most dem anding listeners.

Seven-channel amplifiers

(STR-DA4ES, DA7ES)

In the era of 5.1-channel sound, good A/V systems started including five­channel amplifiers to drive the Left, Center, Right, Surround Left (SL) and
Surround Right (SR) speakers. The common practice is to drive the 0.1 Low­Frequency Effects (LFE) channel from the amplifier built into a powered
subwoofer. In this way, five channels of power became the standard for 5.1­channel sound.

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Now 6.1-channel surround sound is available through sources that include
Dolby Digital EX, dts ES discrete 6.1 and dts ES matrix 6.1 encoding. These
systems add a Surround Back (SB) channel, for even greater realism in surround
sound effects and greater three-dimensionality in the reproduced soundstage.

At first glance, it would seem obvious that if five channel amps were best
for 5.1-channel sound, then 6-chann el amps must be bes t for 6.1-channel sound.
However, the reality is slightly more complex. While 6.1-channel sources can be
correctly handled with a single Surround Back speaker, 5.1-chann el sourc es ar e
best served by separate Surround Back Right (SBR) and Surround Back Left
(SBL) speakers, driven by separate SBR and SBL amplifiers. Separate SBL and
SBR channels enable correct spatial imaging of both 6.1 and 5.1-channel source
material. For this reason, the STR-DA7ES and DA4ES have SBR and SBL
channel amplifiers built in.

To appreciate the advance, it helps to consider movie theater sound for
both 5.1 and Surround EX movie sound tracks. As you probably know, movie
theaters feature speakers behind the screen (Left, Center, Right and Subwoofer),
as well as multiple Surround speakers on the left, right and back walls. The
Surround speakers are driven differently, depending on the type of movie sound
track being reproduced.

5.1-channel movie theater reproduction. Note that the back wall
speakers reproduce TWO signals (SL and SR). ,

In reproducing a "conventional" 5.1-channel movie, the Dolby SA-10
steering decoder is bypassed. In this case, the Surround speakers on the back
wall are split into two groups. One group joins the left wall speakers in
reproducing the Surround Left (SL) channel (the blue signal path in the diagram

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above). The others join the right wall speakers in reproducing the Surround
Right (SR) channel (the red signal path in this diagram).

6.1-channel Surround EX theater reproduction is different. Note that the
back wall speakers reproduce ONE signal (SB).

Reproducing the latest 6.1-channel Sur r oun d EX sound tracks uses the
same speakers in a completely different way. Here the Dolby SA-10 steering
decoder is used to create a distinct Surround Back (SB) channel. So our second
diagram indicates three Surround Channels: SR (signal path shown in red), SL
(shown in blue) and SB (shown in green). As you can see from the diagram, SR
signals come only from the right wall, SL only from the left wall and SB only from
the back wall.

So when a 6.1-channel soundtrack plays, the back wall speakers
reproduce ONE signal. And when movie theaters reproduce 5.1-channel sound,
the back wall speakers reproduce TWO signals. That's why home theater
systems require TWO Surround Back speakers to do full justice to both 5.1 and

6.1-channel sound. And that's what the STR-DA7ES and DA4ES are designed
to support.

Analog downmix

As more and more customers discover the benefits of 5.1-channel home
theater, the market is growing vigorously. However, there is also a population of
two-channel stereo systems that are being upgraded to surround sound. These
may include high-end full-range stereo speakers that the customer has chosen
carefully and simply loves.

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If the stereo pair can reproduce deep bass, the customer may not feel the
need for a subwoofer. In addition, the customer may not want a center-channel
speaker that could never match the sound quality of the existing stereo pair. For
this customer, the best transition to home theater may well be to buy a pair of
surround speakers only. In this case, the customer will be using four speakers to
reproduce material designed for 5.1 speakers. The customer needs to
"downmix" the 5.1 channels to four.

Fortunately, most A/V receivers—and even some DVD players—anticipate
this need. They offer bass redirection circuits that accommodate the full range of
potential playback systems. However, these downmix functions take place in the
digital domain, and that can be a problem.

The problem: how to downmix the L, C, R and SW channels for
customer systems that have no Center channel speaker and no
Subwoofer. (This is often the case for customers migrating from high
quality stereo speakers to multi-channel sound.) The conventional
answer: digital downmixing circuitry. The -6 dB and -3 dB processes
shown here are necessary. But they do tend to muddy the low-level
sound quality. Signal-to-noise performance is also sacrificed.
(Surround channels not shown.)

In order to maintain the correct output level, digital downmixing circuits
must reduce the input volume levels. Otherwise, the downmixed signal would
end up too loud, exceeding the digital full scale level and causing gross clipping
distortion. For this reason, digital downmixing circuits always reduce the input
volume levels. And in the digital domain, reducing the volume means
manipulating the data. Unfortunately, this necessary step muddies some of the
important low-level detail, especially during the quiet passages in music and
movie sound tracks. This loss of information strips away some of the musical
nuances, as well as the sense of soundfield and presence. And noise is also
increased.

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Sony has a better way. Our Analog Downmix accomplishes the goal
without any manipulation of the digital data. So there's no degradation
in sound quality. (Surround channels not shown.)

Sony was determined to offer a better way. With our new receivers, the
data is not manipulated at all. It goes straight into the Digital-to-Analog
converter, preserved in its original form. There's no data loss, no degradation in
signal-to-noise ratio, no loss of nuance or acoustic presence.

Even Sony's multi-channel Super Audio CD players include on-board bass
redirection/downmixing circuitry. These players have the advantage of operating
on 1-bit Direct Stream Digital® signals, as opposed to the multi-bit Pulse Code
Modulation signals of DVD players. However, even the 1-bit digital downmix can
degrade the signal. The Analog Downmix of these Sony ES receivers is a better
choice—no matter what your multi-channel source may be!

For listeners making the transition to multi-channel playback and using
less than five speakers and a subwoofer, high-quality downmixing circuitry is
essential. That's one more reason to choose the new Sony ES receivers.

Optimum Preamplification (OP) with 0.5 dB resolution

Sony's Optimum Preamplification (OP) design varies the preamp negati ve
feedback according to the volume control setting. In this way, Sony balances
gain and volume control settings to achieve a 10-dB improvement in signal-to­noise ratio across most of the volume control operating range. So high resolution
audio is reproduced against a background of silky silence.

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Optimum Preamplification is made possible by Sony's proprietary
CXD9725 integrated circuit.

Sony's Optimum Preamplification (OP) circuit improves the signal-to­noise ratio across a broad range of volume control settings. The latest
version of the OP design controls volume with twice the resolution of our
previous design—0.5 dB steps instead of 1 dB.

In Sony's original OP design, users could vary the volume in 1-dB steps.
Since 1 dB is the threshold of hearing, 1 dB steps are considered the smallest
that people can hear as volume increases. But listening tests have confirmed
that smaller differences are perceptible. That's why Sony's latest OP circuit now
achieves higher volume control resolution. You can increase the volume in 0.5
dB steps, for exquisite sonic control.

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