Multimoog Musical Instrument Manual de Serviço descarregar pdf (Página 20)

The

path

from

the

audio

output

of

the

sound

source

through

the

modifiers

to

the

speaker

is

called

the

"audio

signal

path."

The

audio

signal

path

carries

electrical

signals

that

are

to

be

made

audible

by

the

speaker.

Notice

that

the

sound

source

has

only

an

audio

output

since

it

actually

generates the

audio

signal.

The

modifiers

must

have

both

an

audio

input

as

well

as

an

audio

output

since

the

audio

signal

to

be

modified

flows

through

them.

At

this

point,

let's

use

appropriate

synthesizer

terminology.

The

pitch-generating

module

is

called

an

"oscillator;"

the

timbre

modifying

module

is

called

a

"filter;"

and

the

loudness

modifier

is

called

an

"amplifier."

The

diagram

below

shows

the

typical

synthesizer

modules

used

in

the

audio

signal

path

to

establish

a

pitched

musical

voice:

TYPICAL

AUDIO

SIGNAL

PATH

MODULES

Once

this

typical

setup

is

established

we

have

a

musical

voice.

But

how

can

we

control

this

voice-

sound

source

and

modifiers—to

make

music?

The

synthesizer

is

an

electrical

instrument;

it

responds

to

electrical

signals.

But

humans

can't

handle

and

manipulate

electricity

directly.

So

we

use

a

mechanical/

electrical

device,

like

a

potentiometer

(pot)

that

will

let

the

two

machines

(human

and

Multimoog)

communicate.

For

the

human,

the

pot

has

a

knob

that

can

be

turned

by

hand;

for

the

Multimoog,

a

change

in

the pot

setting

changes

an

electrical

value

that

the

Multimoog

understands.

In

fact,

important

elements

of

sound

on

the

modern

synthesizer

are

controlled

by

voltage

levels.

The

modern

synthesizer

is

"voltage

controlled."

If

we

put

a

pot

on

each

module

above

we

could

control

its

particular

function—pitch

generation,

timbre

or

loudness

modification—with

a

change

of

voltage

by

turning

the

pot.

With

the

Multimoog,

an

increase

in

voltage

that

is

controlling

an

oscillator

makes

the

pitch

rise;

an

increase

in

a

voltage

that

is

controlling

the

filter

causes

the

timbre

to

brighten;

and

an

increase

in

voltage

that

is

controlling

the

amplifier

makes

the

sound

louder.

So

far,

we

have

a

voltage

controlled

instrument

that

can

be

played

by

turning

knobs.

If

you

had

three

hands,

you

could

make

some,

pretty

good

music!

Making

music

by

playing

knobs

would

be

very

restrictive.

Fortunately,

with

the

synthesizer

we

are

not

restricted

to

this

sort

of

manual

control.

The

synthesizer's

important

modules

can

be

controlled

with

voltage

from

any

source.

So

we

create

a

control

input

on

appropriate

modules

to

accept

control

voltages

from

any

source.

To

avoid

confusion with

the

audio

(sound)

signals

flowing

from

left

to

right,

let's

think

of

these

control

inputs

as

appearing

on

the

bottom

of

each

module,

as

shown:

CONTROL

INPUTS

OSCILLATOR

FILTER

■

•»

AMPLIFIER

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TO

MONITOR

5

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25

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