MORE INFORMATION
ABOUT DlmTAL AUDIO
The DX is not a Synthesizer. It does not synthesize sound. What it does is play back
sounds from it memory. These sounds are stored as numbers
, inside special inte-
grated circuits called ROMs (Read Dnly Memory) which are pre-
programmed. Before
explaining how digital audio works
, let's digress for a minute and discuss how regular
analog audio works:
Sound
, as far as your ears are concerned. is caused by very small but regular changes
in atmospheric pressure. The air moves back and forth
, over and over
, alternately
pushing and pulling on your eardrums and the rest of your body. When these waves of
air occur between 20 and 20
000 times per second
, your brain perceives them as
sound. Anything that makes noise must ultimately disturb the air in this sort of regular
way. Look at the low frequency speaker in your sound system. If you turn the voiume
way up (don
t damage your speakers
, though!) you will see the speaker (and feel the
air near it) moving in and oUl
, in exactly this sort of regu(ar movement.
So what any analog audio system does
, is provide a pattern of regular movement
(oscilation) for the speaker to move in
, so that you feel the air moving in this same pat-
tern so that your brain can translate all this into sound and you can HEAR! Look at a
, phonograph record
very ciosely and you wil see the same repeating wiggles that are
amplified by your amplifier to move your spekers.
Digital audio stores
, not the oscillations that move your speakers
, but a series of num-
bers that represents those oscilations. Take the groove from that phonograph record
and, in your mind
, stretch it out in a straight line and piace it on a piece of graph paper.
Now if you went from the left end of the graph to the right, and everY centimeter wrote
down a number that represented how far that phonograph wiggle moved up and
down, you would become a recorder of digitl audio. Now
, if you took another piece of
graph paper and plotted all those numbers that you just wrote down
, you would do
what a digital audio recorder does to play back.
So what is programmed inside an ROM in the OX is a series of numbers (lots of num-
bers!) that represents the sound of a snare drum. Another one has the representation
of the sound that a cymbal makes
. and so on, for all of the sounds.
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