Accuphase DG 28 Brochure

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DIGITAL VOICING EQUALIZER

DG-28

o Vaicing equauzer wxm tuuy dlgital signal processing a 64 filter cells
connected In parallel o Htgh-preclsion adjustment in 64 lrequency bands,
using tle~oclave spacin OLarge d>splay panel shows graphical lrequancy
response curve IBuill-in analyzer and sound field compensation tunctions
0 Automatic measurement and adjustment 0 Oplton boards allow
connection at analog equipment 0 Supplied remote commander

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The Digital Voicing Equalizer DG-28 has the power to effectively reshape your
listening environment. It uses ultra high-speed DSP chips and super advanced
digital signal processing technology to measure the sound field at the listening
position and to compensate for any acoustic deficiencies. Internally, the DG-28
operates entirely in the digital domain. Highly precise pin-point adjustments are
possible thanks to 64 parallel-connected filter cells per channel, yielding 64
frequency bands spaced only 1/6 octave apart. A large LCD panel provides an
intuitive graphic view of frequency response and adjustment settings. Rear-panel
option board slots allow connection of analog equipment as well.

What ls a Voicing Equalizer?
This somewhat unusual term was chosen to
symbolize the advanced capabilities of the DG-
28. While this product is a full-fledged high-
precision graphic equalizer in its own right. it also
incorporates a sophisticated system for
automatic sound field compensation.

It divides the audible frequency range into
distinct bands (voices). and lets the userchoose
a target response curve that is then expressed
(voiced) by the unitthrough a process of precise
measurement and adjustment steps.The result
is full control over frequency response
characteristics at the listening position.

Development of the Digital Voicing Equalizer 06-28
was made possible by Accuphase's advanced
knowledge of digital signal processing technology
for pure audio applications. Without suffering any
degradation in signal quality. precise sound field
control has now become a reality. And whats more.
the DG-28 is amazingly simple and intuitive to use.
To achieve truly superior music reproduction in a
home environment, the characteristics of the
speakers as well as the listening room itself have to
be taken into consideration. Only when these aspects
are under control. the stereo sound stage will come
alive in all its splendor. The 06-28 lets the natural
ambiance and musical presence of the source
material emerge with unrivaled clarity and authority.

The DG-ZB not only has the power to adjust and
line-tune frequency response. it also incorporates a
signal tone generator and comes with a dedicated
measurement microphone of high quality. allowing

sound field measurement and compensation. lf ana-
log circuits were employed here. a number of
problems were bound to arise. such as component
aging. changing circuit characteristics due to
fluctuations in ambient temperature, circuit tuning
imprecisions. sound quality deterioration depending
on adjustment position. etc.The digital approach on
the other hand does away with all these problems. It
also is highly impervious to externally induced noise.
The type of narrow and precise filters that are
required for frequency adjustment can be designed
very effectively. using DSP (Digital Signal Processor)
chips. To assure absolutely top-level performance.
the DSP data path in the DG-28 is 24 bit wide for
input/output and 48 bit for internal processing. The
ultra high-speed DSP chips require no more than 40
nanoseconds lor an arithmetic operation. Two such
chips are used per stereo channel, resulting in a to-
tal complement of tour processors.

64 Filter Cells per Channel Connected in Paral-
Iel

Filter cells are a vital area of any equalizer. because
they determine characteristics such as center
frequency and level range.The DG-28 uses a lull 64
cells per channel. In lhe world of automobiles. it might
be likened to a 64-cylinder engine. which is why
Accuphase likes to call this part the "lilter engine".
Within this analogy, the DG-28 can be described as
having two filter engines. one for each channel.

Internally. the lilter cells are connected in parallel.
as illustrated by Figure 2. This type of connection
has various advanlages for a multi-stage filter.
Calculation errors will not add up. and any tolerances
will be averaged out. thereby reducing noise.

Accuphase has developed special algorithms for
linking and controlling operation of the filters.

mm +

46" r

donor

22.0er
- } nun our. x 6

Figure 2 Filter englne with 64 flltercells connected In
parallel (one channel)

Currently unused tiltercells are removed entirely from
the signal path. to preclude any possibility for signal
quality deterioration.

High Precision Adjustment From 16 Hz - 22.400
Hz in lie-Octave Steps (54 Frequency Bands) or
1/3-Octave Steps (32 Frequency Bands)

Almost all listening rooms are shaped in rectangular
fashion. with walls meeting at right angles.This gives
rise to standing waves which are an acoustically
highly undesirable phenomenon. Especially in the
area of 200 Hz and below. drastic frequency
response irregularities are very common. In the
medium and high frequency range. often the speaker
units themselves have response curves which look
like a succession of peaks and dips.The DG-28 can
even out such irregularities. bringing the response
curve much closerto the ideal shapeThis is possible
because the audio spectrum is divided into 64 bands.

automated adjustment of overall response
characteristics. Ultra-precise digital filters
provide 1/6-octave resolution. dividing the
audio spectrum into 64 frequency bands.

something that invariably involved a mfpmm
quality penalty when implemented in the

analog domain. A large liquid-crystal l-M
display panel shows response in graphical out...

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form. making adjustments immediately
evident at a glance.

In conjunction with the Digital Preamplifier
DC-SOO. the DG-28 comes really into its
own. With this combination. the signal
remains entirely in the digital domain. right
up to the preamplifier outputs. Signal

degradation is totally absent, Optional WI
5

option boards can be used to
accommodate a wide variety of analog
equipment as well.

Fully Digital Equalizer

As can be seen from Figure 1.
sophisticated digital signal processing
technology is used in the DG-28 in order
to integrate two main functions. namely

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Figure i Block diagram of 06-23