AM 334-01-502
4
A PURPOSE OF THE MANUAL
This manual, part of the DX 400/500 manual series,
complements the other manuals in the series by presenting
the technical principles behind the operation of the DX.
400/500 organs. It is not necessary to know the information
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 work. Some acquaintance with
microcomputer terminology will help in understanding the
principles presented. The manual also presents practical
procedures for addressing the question, "What to do if. -
B. TECHNICAL CONCEPT
I. Traditional Organ Systems
To put the new DX digital organ concept in proper
perspective, we will first briefly look at three approaches to
electronic organ technology.
1. Analog Organs
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.
II. The DX 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
• five 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 programs
read into the organ from a cassette recorder 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
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