T+A Elektroakustik DD 1535 R Operating Instructions Manual Download

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The



surround system

Multi-channel

reproduction

based

surround

technology  does  indeed  open  up  new  worlds  of
experience,  but  the  technical  implementation  of  a  multi-
channel  surround  system  does  involve  a  number  of
potential  pitfalls.  Many  existing  surround  systems  have
gained  a  reputation  for  no  more  than  moderate  sound
quality, especially when used in normal stereo mode.

The  reason  for  this  lies  in  the  tiny  magnitude  of  the
sensitive  analogue  stereo  signals.  These  signals  are
measured  in  the  range  of  just  a  few  Millivolts
(thousandths  of  a  Volt),  and  unwanted  interference  to
these  signals  can  be  perceived  by  the  human  ear  even
when  a  thousand  times  smaller  than  that.  Conventional
surround amplifiers feature a single case in which digital
signals and high-frequency video signals live in the same
space  as  the  sensitive  analogue  signals,  and  this
represents  an  open  invitation  for  interference  between
the various signals.

This compromise solution is entirely unacceptable to us
at



, so for our surround system we developed an

arrangement  in  which  the  various  signal  processing
sections  were  kept  entirely  apart.  The  system  therefore
comprises  two  specialised  devices:  an  analogue  two-
channel  stereo  amplifier  is  used  to  process  high-quality
stereo  signals,  while  the  digital  surround  signals  are
processed  in  the  surround  decoder  which  is  an
independent machine.

In the



system the analogue and digital sub-

assemblies  are  separated  from  each  other  completely,
and  this  eliminates  the  danger  of  interference  to  the
delicate  analogue  signals.  The  net  result  is  that  there  is
absolutely  no  danger  of  a  loss  in  quality  in  analogue
stereo reproduction.

To make it possible to integrate the surround decoder
easily into an existing



system, we developed the



surround interface (TASI), which also provides the

means to process and reproduce analogue signals, e. g.
Dolby Surround encoded source material.

This  interface  is  the  key  to  integrating  the  decoder
elegantly  into  the  overall  system.  At  the  same  time  the
decoder  has  absolutely  no  effect  on  normal  stereo
signals,  since  it  is  completely  removed  from  the  signal
path during normal stereo operations.

Not even the length of the signal paths is changed; in
stereo mode all signals remain in the pre-amplifier
section of the amplifier, i. e. they are not forced to make
a detour through the surround decoder.

When the system is used in Pro Logic II mode, the TASI
interface also ensures that the decoder is looped in at
the ideal point and at the optimum level in terms of signal
processing, i. e. directly after the source selector switch.

An additional advantage of the TASI interface is that it
makes it possible to exploit the superb output stages of a
typical



stereo system for the front channels when in

surround mode.

To  ensure  that  the  sound  from  the  whole  system  is  as
balanced and harmonious as possible, the output stages
built into the decoder are identical in circuit design to our
stereo  output  stages.  This  design  philosophy  ensures
identical frequency, phase and transient behaviour on all
channels,  combined  with  perfectly  balanced  dynamic
characteristics.

The



surround philosophy also provides further

advantages: two separate pre-amplifier circuits are
present, each with its own volume and tone control
functions: a stereo pre-amplifier and an independent six-
channel pre-amplifier in the surround decoder.

It is therefore possible to adjust the levels and tone
settings separately to meet the different requirements for
stereo and surround modes. When you switch mode, the
correct settings automatically take effect.

TASI

alo

e S

DECODER

ita

l S

urr

ProLogic

Front

Sub In

Sub Out

e S