Wersi CD 600, Assembly Manual

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AM 320-01-808
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I. PURPOSE OF THIS MANUAL
This manual is supposed to complement the assembly
manuals and the User's Guides by presenting the
technical principles behind the operation of the CD
6/7/8/900 organs. It is not necessary to know the
information given in this manual to assemble the
organ. However. it is possible to gain a better
understanding of the musical possibilities of the organ
by learning the technical aspects of its operation.
Also, knowing such information can be a big help if
you ever - hopefully never - have to troubleshoot the
organ.
The technical data is presented in a manner that is aimed
more at the interested layman than the electronic specialist.
Rather than going into fine detail about how each circuit
functions, the text gives more of an overview of how the
various subassemblies and modules work.
11. TECHNICAL CONCEPT
A. Traditional Organ Systems
To put the new CD digital organ concept in proper
perspective, we will first briefly look at three
approaches to electronic organ technology.
1. AnalogOrgans
In this type-and this is the type most commonly used-
sine wave. tones are produced by a tone generator,
selected by mechanical or electronic switches,
processed in filters to produce the desired voicing,
amplified and applied to a speaker.
Of interest here is that it is the hardware (the system
components) alone that determines the capabilities of
such an instrument.
2. Quasi-Digital Organs
These organs are touted as being "digital;' especially
in the promotional literature, but a closer look shows
that they do not merit this tag. To be sure, they
employ digital support techniques-serial data
transmission, for example-along with complex IC
circuitry. But the tones are still developed and
processed mainly by analog means.
3. Digital Systems Using Original Sounds in
Memory
Committing original musical sounds to a digital
memory is a widely know technique used in digital
synthesizers and rhythm units. In moderately priced
instruments, reflecting moderate technical
sophistication, the sounds of instruments such as
trumpets, violins and pianos are stored exactly as
those of drums, cymbals or cowbells-in short, single
tones.
These original tones are read out when the instrument
is played and are assigned to the desired instrument
range according to a clock frequency controlled from
the keyboard. A digital-to-analog converter changes
the digital data back into audible analog tones. The
tones sound rather genuine when played in the tonal
range of the original instrument; however, the tones
become less and less true the further the player
deviates from this range. This is because the tone
formants cannot be held constant over the entire range
of the keyboard.
B. The CD System With Full Digital Tone
Processing
In this new Wersi technology, a microprocessor system
computes all the sounds and digital.to-analog
conversion produces audio tones from the resulting
data. The processor system consists of a master
processor and up to eight co-processors, known as
slaves.
The slaves are responsible for the correct processing of
the tones, receiving essential data such as pitch, volume
(envelope amplitude), frequency, vibrato, formants, etc.
from the master processor. The master processor sends
new data to the slave anytime there is a change in input
status, whether it is a registration change or a new key
stroke.
The outstanding advantage of this system is that a wide
range of musical forms can be achieved, even though
the hardware never changes. It is the software-data pro-
grams read into the organ from a memory card or a
computer-that creates so many musical possibilities.
The data in the organ's memories can be added to or
changed completely, giving the organ a whole new
repertoire, if desired. Sounds from liturgical organ to
synthesizers to conventional musical instruments are
possible through software.
A further advantage of this system is that a given sound
quality, once achieved and filed as software, will be the
same when reproduced by any organ in the series, since
hardware variations will have virtually no effect on the
sound properties.
Additional special effects can be achieved through
further processing of the digitally developed voices via
a voltage-controlled filter (VCF) and a phase vibrato
(Wersivoice) circuit.
Apart from its contrast to other organ systems, the CD
concept offers the most possibilities in terms of sound
and functions, and is the most flexible concept for the
electronic production of individual musical voices yet
presented.
C. The CD System Block Diagrams
1. The Complete Organ
The master (MST8) contains the Central Processing