Panasonic EURO 4 Chassis, Technical Manual

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22. Pro Logic Processing Overview
22.1. Introduction
Dolby Pro
.
Logic processing which has been
incorporate into selected Panasonic models is
performed on an additional board, this additional
board being the K-Board.
Although this K-Board (TNP8EK004AA) is able to
perform Dolby Pro Logic processing, to produce the
Centre and Surround channels additional external
amplifies and speakers are required.
The normal listening function used without these
additional Centre and Surround speakers is a feature
known as 3D Active. This feature uses the normal
internal TV speakers to provide a wide ambience
effect enveloping the viewer in sound effects. This
feature will be looked at in detail later.
Where the additional centre and surround channels
are being used for full Dolby pro-logic processing a
total number of five speakers are used. The five
speakers being Left, centre, Right, and two surround
speakers, the surround channel being a mono signal.
The first of these five speakers, the centre speaker is
used to ensure clearer positioning of sounds.
In addition to this centre speaker there is also
provision for external front left and right speakers via
the phono output to an external amplifier, however
where this option is not used the internal left and right
speakers of the TV are used to provide directional
sound effects. While the two external rear speakers
provide us with the surround effects.
The Panasonic TV can also be used in Phantom
mode which does away with the centre speaker
format and uses only the front left and right speakers,
and surround speakers.
The left and right audio signals have the centre signal
mixed equally between the left and right channels,
this mixing being performed by the dolby processing
board. The left and right channels now create an
imaginary centre or PHANTOM centre.
Before we take a more in-depth look at Pro Logic
decoding
as performed by the K-Board
TNP8EK004AA, we will look at the basic concept of
the encoder.