ARP Instruments Omni Service Manual

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OMNI

Model

2480

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SERVICE MANUAL

THE

INFORMATION DISCLOSED MAINTENANCE DISCLOSED

TO

AS

OTHERS

YOU

CONTAINED

SOLEY

APPROPRIATE.

FOR PURPOSES OF

WITHOUT

ARP INSTRUMENTS, INC.

Needham

320

Newton,

MA

(617) 965-9700

Document Number 90020000

ARP INSTRUMENTS, INC.

HEREIN

THE

IS

CONFIDENTIAL

IT

IS

NOT

EXPRESS PERMISSION OF ARP

INSTRUCTION

TO

BE USED BY

AND

Street

02164

PROPRIETARY

AS

TO

YOU

FOR

INSTRUMENTS,

TO

OPERATION

ANY

OTHER

ARP

INSTRUMENTS,

OF

THE

PURPOSE,

INC.

NOR

IS

INC.

IT

EQUIPMENT

TO

IT AND

BE

IS

OMNI Model

2480

SERVICE MANUAL

TABLE

1.

INTRODUCTION

1.1

Product Description 2

1.2 Specifications 2

1.3

Function

2.

THEORY

3.

CIRCUIT

3.1

Upper

Lower

3.2

3.3 String

3.4 Synthesizer

3.5 Synthesizer Board 10

3.6

Phaser

3.7 Power Supply

4.

ASSEMBLy/DiSASSEMBLy

5.

GENERAL

6.

CALIBRATIONS

SCHEMATICS & LAYOUTS

7.

Description 3

OF

OPERATION

DESCRIPTIONS

Voicing

Control

Board 10

INFORMATION

OF

CONTENTS

Board 5

Board 6

Board 8

Board 9

5

11

12

13

14-33

8. PARTS

LIST

34-36

1

SECTION 1

INTRODUCTION

1.1

Product Description

The

ARP

OMNI

offers polyphonic sizer synthesizer sounds synthesizer

piano,

The

by

stereo ARP's this

effects The and

tone

sources

sound

string

product

computer-grade

reliable.

modification.

sections

simultaneously.

section

and

clavi

net

and

synthesizer

outputs

now-famous

as well.

or

output

its

1.2 Specifications

I.

Controls

A.

String

Section

1.

Instrument a.

Violins

b.

Violas c. Cellos d.

Bass

2.

String a.

Attack b. Release

B.

Synthesizer

1.

Synthesizer a. 4'and

2.

Synthesizer a.

8'

3.

Voltage a.

VCF

b.

Resonance

c.

ADSR

d.

LFO

e. Pedal &

4.

LFO

Speed

5.

Synthesizer

a.

Sawtooth

b.

Dynamic

6.

ADSR a.

Attack

b.

Decay

c.

Sustain

d. Release

C.

General

Controls

the

and

allow

The

permits

without

on

the

systems

The

own

signals

switching

Selection

(4')

(8')

(16')

Envelope

Time

Section

Waveform

8'

Bass

and

16'

Controlled

Freq

depth

Acc.

Slider

Waveforms

Time

Level Time

unique

the

versatility

Separate

orchestral

total

such

single

sections

rear panel

interface

OMNI

can

tv

mechanisms

Controls

Switches

Filter

depth

Pulse

combination

string

and

symphonic

variability

sounds

note

limitations.

may

be

of

accept

other

instruments.

Switches

of

synthe-

of

as brass,

separated

the

OM NI.

applies

external

are

of

and

the

to

fast

1. Master

2. Bass

3.

4.

5.

II.

Outputs

- A. Main 1_

2.

'--

B.

Synthesizer

1.

--"Can

stereo

C.

Gate

1.

2. Trigger:

D.

Foot

1.

III.

Miscellaneous

A.

Keyboard

1. 4

B.

Pedals

1.

Sustain

C.

1.

D.

Materials

1.

2. Rigid

3.

4. Glass-epoxy

5.

E.

Weight

1.

Volume

Volume String/SYnthesizer Waveform Synthesizer-to-Modulator

Outputs

High Level

Low

be used

effects.

Out

Gate:

2 microsec.

Switch

Standard

octave

at

Filter

filter

Foot piano

Aluminum

Solid

Industrial-grade

and

33

RMS

TYP.

Level

RMS

TYP.

Output

Level

TYP.

and

Trig

Tini D

Tini D Jack;

and

ARP

one

and a half

control

brightness

Switch

switch

high-density

walnut

controls

pounds

Enhancement

Cannon

1/4"

simultaneously

keyboard,

phone

1/4"

phone

Out

Jack;

duration

Foot

accessories

pedal

works

chassis

end

blocks

circuit

electronic

Mix

XLR, 1K,

0,

+1

Pedal

split

octaves

for

like

particle

boards

Switch

1OK,

10K,

for

OV

0,

+10V

for

from

foot

sustain

board

components

2.5V

.8V

discreet

bass

low

co~1

pedal

base

RMS

pulse,

voices

end

of

.

on

2

3 2

16

17

1.3

Function Description

Mix Control:

1

string

voices

LFO Speed: Varies

2

Frequency

Master Volume:

3

the

Waveform Enhancement:

4

produced

sound.

Chorus Phaser:

5

through

reduces pressed

string

mixed

output

Oscillator.

output.

by

the the

the

Determines

and

the

synthesizer

the

Determines

the

Omni

Routes

string

section's

phase

shifters

synthesizer

as well.)

the

balance

voices.

frequency

overall

Alters

to a hollow

the

synthesizer

phase speed.

output

appears

FOOT

of

the

of

the

Low

volume

waveforms

like (square)

shifters

(When de-

of

output

and

on

the

r SYSTEM INTERFACING I r VCF CONTROL

SUSTAIN

SWITCH

TRIG

OUT

11

VCF

synthesizer

12

VCF LFO Slider:

GATE

ou'

ADSR

13 VCF Pedal

range

of

14 Violin

ranges.

15 Bass, Cello:

(low

note

only).

Attack:

16

17 Release:

string

section.

and

external

and

priority,

Determines

section

INPU1=S

ACCESSORY PEDAL

21

Slider:

22

Determines

Accessory Slider:

pedal

or

Viola:

Selects

(also

Selects

bass

lowest

attack

the

effects

I

brightness

depth

accessory.

the

string

pitch

octave

of

string

final release

synthesizer

of

tremelo.

Determines

pitch

ranges a

and

half

section.

time

release).

of

Synthesizer

6

tion's

pitch

7

Synthes/~er

8

9

10

sizer's and

ADSR

bass voices

4'

voices

half).

Envelope Generator:

attack

and

sizer

section.

VCF Frequency Slider:

frequency

VCF Resonance Slider:

resonance

8',

4':

ranges.

Bass

in

decay

cutoff

("wow"

Selects

8',

and

bass range

characteristics

point.

effect).

16':

disables

Sets

the

Selects

Sets

synthesizer

(first

octave

Determines

of

the

VCF's

degree

the

sec·

synthe-

and

synthe-

initial

of

VCF

8'

the

18

Bass Volume:

synthesizer

Sustain

19

foot

a

slider

20

Gate

connect

21

Accessory Jack:

input ternal Sample effects.

Pedal Jack: Used

22

Foot

switch

settings).

and

to

so

that

sources

and

16',8'

Switch:

is

depressed

Trigger

other

VCF such

Hold

Determines

and

bass

and

Sustains

(regardless

Output

synthesizers.

Connected

may

be

as

the

outputs,

to

connect

bass

cello.

all

Jacks:

to

VCF

controlled

ARP

Sequencer

etc.

VCF

volume

notes

of

release

Used

control

for

special

filter

for

when

by

ex-

pedal.

to

or

3

~

MASTER

OSCILLATOR

1 line

TOP

OCTAVE

DIVIDER

SIMPLIFIED OMNI BLOCK

..rt...rL ..rt...rL

12

lines

FREOUENCY

DIVIDERS

~

49

lines

WAVE

SHAPERS

BUS

RODS

BASS

I L

..rt...rL

2.!.J.ines

L.-.t..

DIAGRAM

GATE

CIRCUITS

t

49

lines

KEYING

CIRCUITS

21 lines

~

BASS

PRIORITY

CIRCUIT

t

4'

-

8'

-

8'

~

16'

~

1-----------------

I

--+--

PHASER

f-----

~

t t

STRING

-...:z::.

chorus

r--

I

AR

SECTION

switch

I

r-

STRING

----------------~

r---------------~

I I

~

VCF I I

t

STRING

VCA

I

VCA

t

~

I

:

I

~

,------.

OUTPUT

M/X

MIX OUTPUT

SYNTH OUTPUT

,;'"

0

ESIZER

/

SYNTHESIZER

L

ADSR

SECTION

~

SECTION

The

OMN I master scale octave the remaining squarewave a the

The transistor string tor

connected (how

determined

input.

The routed section.

oscillator

integrated

divider

instrument.

sawtooth

waveshape

tones

section

gating

long

outputs

to

2

's

tone

pitches

outputs

form

from

gating

and

arrays

to

each

the

by

of

the

THEORY

generator

at

500

circuit

produces

Frequency

from

of

(the

to

a

the

waveform

arrays

the

synthesizer

are

key.

note

remains

the

release

all

the

string

circuitry

kHz.,

top

octave

the

highest

the

top

each

divider

waveform

differentiated

which

route

'keyed'

gating

The

release

capacitor

section

on

after a key

arrays

OF

OPERATION

consists

which

drives a large

divider.

twelve

dividers

octave

are

waveshaped

enhancement

generator

the

section.

by

an

time

on

are

and

the

of

The

top

tones

in

derive

divider.

squarewave).

signal

The

of

each

summed

synthesizer

alters

are fed

to

transis-

RC

circuit

each

release)

gating

the

The

to

the

key

and

a

is

The

string shifters from

the processed control trolled circuit).

The the Voltage controlled synthesizer section selected.

the

string

together output output

the

by

synthesizer arrays

Chorus

section

is

section

which

gating

through a Voltage

attack

the

through a Voltage

Controlled

by an

output

phasers

The

Phaser

in

of

the

provided

consists

modulate

circuits.

characteristics.

release

section

Amplifier,

ADSR

can

when

the

speed

of

is

selected.

and

the

synthesizer

the

Mix

Circuitry

instrument. A separate

for

stereo

of

the

sawtooth

The

Controlled

capacitor

processes

Controlled

Envelope

be

routed Chorus

the

phasers

effects.

three

phaser

(The

the

both

through

Phaser

is

The

section

and

parallel

waveforms

outputs

Amplifier

release

on

each

gate

outputs

Filter

of

which

Generator.

the Switch

reduced

outputs

are

routed

synthesizer

phase

are

to

is

con-

gating

of

and

are

The

string

when

of

the

summed

to

the

is

SECTION

3

CIRCUIT

3.1 Upper Voicing Board

GENERAL: Master Dividers, Wave

Keying

ten

Gate

Keying Lower tics

for

3.1.1

(Refer

L1

and approximately tor

can

(externally

waveform

to

the

Scale

Integrated highest (C6·C7).

The

Oscillator,

Circuits

Circuit

Circuits

Voicing

th

is

board.)

MASTER DIVIDER

to

Upper

01

produce

500KHz.

be varied

accessible).

from

Top

Octave

octave

Upper

Top

Shaping

for

keys

/.C.'s.

and

Board.

OSCI

Voicing

by

the

Master

Divider,

Circuit)

(square

Voicing

Octave

for

21

through

The

Gate

I.C.'s are

(Note:

LLATOR

Schematic,

a 0

to

The

adjusting

Z1

divider

waves)

DESCRIPTIONS

Board

contains Divider I.C., tones

C7

through

49

and

remaining

There

-15

frequency

the buffers Oscillator

Z2.

AND

volt

Z2

which

of

are

core

and

is

the

Waveshaping,

located

two

TOP

sheet 1 of

sine

of

and

a LSI

produces

Frequency

six

of

on

schema-

OCTAVE

wave

the

oscilla-

of

the

squares

supplies

(Large

instrument

the

C4,

the

2.)

at

coil

the

3.1.2

The

o

(Refer

square

clock

inputs

which

produce

wave

outputs

inverters

DIVIDER

to

Upper

wave

of

Z9-Z16.

AND

Voicing

outputs

CD4520BE

square

waves

the

WAVE

SHAPING

Schematic,

from

Z2

divider

for

each

CD4520BE's

CIRCUITS

sheet 1 of

are

supplied

chips

key.

The

are~uffered

2.)

to

the

(Z3-Zl)

square

by

i

Waveform

it

The

square

are

differentiated selected the

negative resulting

converter

waves Trom

for

each

portion

in

sawtooth

and

waveform

inverters

by

capacitors

frequency).

of

the

shaped

enhancement

Z9·Z13

C17-C49

CR1

through

differentiated

waveforms.

and

from

(values are

CR41

square

By

altering

Z2

clip

wave

5

the

DC

bias (P6-7,

the

negative permitted Waveform "hollow"

3.1.3

(Refer

Each to a 22uf resistor. (The When a key to

-15

to

0 volts sets be varied by Control key circuits;

to

type

KEY I

to

Upper

key

contact

The

negative

volts.

Board.

(indicated

one

Waveform

portion

Enhancement

NG

electrolytic

for

pass

through

sound.

CI

RCUITS

Voicing

(P7-5, P7-4,

capacitor

side

of

is

depressed,

The

time

the

release

the

release slider

The

by

letters

8',

one

of

key

the

differentiated

diodes

is

Schematic,

capacitor

is

normally

the

capacitor

the

capacitor

time

voltages

KV) are

for

4'.

Control

selected

P7-3,

capacitor

of

(R31)

Bus)

waveform

CR1-41

resulting in a

sheet 2 of

etc.)

is

through a 4700hm

charged

is

at

-15

is

takes

each

note

on

produced

supplied

some

when

the

connected

to 0 volts

volts.).

discharged

to

recharge

and

can

the

String

for

each

to

two

gate

of

2.)

as

the

inputs

to

the

devices. Five

is

for

4'

used one

key

controls

The

Upper

arrays

and

the

Lower base pin (7) forms

are

supplied resistor pack voltages also as tor voltage sistor the cuitry

Z30

through

the

keying

remains

in

collector

(e.g.

(denoted

drops

the

pitches

three

Voicing Board. All

pins 5

from

and five

two

Voicing Board

8'

arrays;

grounded.

to

Tone

G 4 and 6 to by KV)

150Kohm

voltage

off.

When a

to

-15

array

and

of

the

array

pin 12

3.2 Lower Voicing

gate

chips

the

Each

an

emitter

is

supplied

are

resistors (e.g.

is

at

or

key

volts,

permits

and

of

Z31

Board

of

the

for

8'

pitches.

at a time

contains

remaining

of

supplied

near

is

depressed,

which

out to

three

arrays

the

arrays

the

sawtooth

through a 100Kohm

through

12

of

Z31.).

to

the

KV21).

0 volts,

turns

on

the

signal

to

the

14).

arrays

are

Therefore,

(4'

and

8').

4'

gate

are

have

the

wave-

resistor

Keying

emitters

As long

the

transis-

the

keying

the

tran-

to

pass

mixing

cir-

on

to

KEY

CONTACT

BUS

ROD

-15V

3.1.4

GATE

(Refer

There (TDA470) tone Gate with

to

are a total

generator

has

common

Keying

CI

Upper

in

the

ten

collectors

sections

transistors

-15

470 ohm

,

3.3K

~~WmJi

SAWTOOTH WAVE

_IL

SUPPRESSION TRIGGER

AND

STRING

RELEASE

CONTROL

and

Gating circuit

RCUITS

Voicing

OMNI

Schematic,

of

10

which

to

the

(on a common

and

150K

100K

(TONE)

gate

gate output

bases.

TDA470 TRANSISTOR ARRAY

sheet 2 of

transistor

signals

section.

The

emitters

OUTPUT

,

~-------

arrays

from

substrate)

-

----

2.)

the

Each

serve

GENERAL: Bass

Low circuitry, circuitry, keys 1

through

G3,

and

3.2.1

The

Voicing detailed

3.2.2

The

through fixed, control polyphonic and

The to

shaping

WAVESHAPING, CI

(Refer

board

(Refer

note, lowest

(only) in

to

Waveshaping,

are a continuation

Board. See

descriptions.

BASS LOW

to

8'

and

low

octave

20).

the

over

generates

function

route

the

circuits

The

Lower

Note

Priority

Gate

Sensing

8'

and

16'

20,

Gate

Waveshaping

RCUITS

Lower

Voicing

Gating

sections 3 1.2,

Lower

Voicing

16'

Bass

note

priority.

and

a half

The

release

the

tones,

only

of

the

square

Bass

control

Bass

the

square

wave

section

(through

circuitry,

Bass

NOTE

section

section.

Bass

Voicing

circuitry,

circuitry, circuits for

tones

KEYING

Schematic,

and

Keying

of

the

PRIORITY

Schematic,

of

The

Bass

of

the

time

on

the

Priority

waves.

Low

Note

of

the

lowest

to

the

CR41-60)

Board

4'

and

Suppression

Keying

for

tones C2

AND

sheet 1 of

circuits

of

Unlike

8'

3.1.3

sheet 2 of

the

OMN I

section keyboard the

Bass

front

the

Circuit

Priority

note

and

16'

for

on

contains

8'

Mixing

Trigger

circuits

C2

through

GATE

on

the

Upper

and

3.1.4

CIRCUIT

is

covers

(Keys

section

panel

has no

4'

and

receives

circuit

depressed

Bass Wave-

processing.

the

for

G3.

3.)

this

for

3.)

single

the

1

is

8'

is

6

I

The may

Bass

Waveshaping

only

accept

one

circuits

waveform

are

monophonic;

at a time.

they

(Z33-Z47) keys

higher

to

than

transmit

the

one

serially a logic 1

depressed.

state

to

all

Square Voicing three outputs only Z33B are

NOTE: section are COSMOS (Complimentary

wave

tones

Board

frequency

input

nor

of

these

when

the

pin 6 is a square

at

logic

0.).

All

logic gates in the Bass

C2-G3

gate

nor

other

for

gates

two

wave

are

routed

dividers

each

are

inverted

inputs

only

from

the

Upper

to

one

input

key

(Z33-Z39).

square

waves

are a logic 0 (e.g.

if

pin 4

and

Low

Note

Priority

Symmetry

of

The

pin 3

Metal Oxide Semiconductor) devices. For this

they

particular application, ground voltage voltage

and

-15

between

volts. Therefore, a logic 1

ground

-7.5

~

------I~

~~I-----i-

6

,

(A)

I

ENABLE

6

KEYING

The only and

The

Z33B,

provided

circuit

(B)

VOLTAGE

output

(C)

of

the

when the Enable (A)

when

the Keying voltage is less than -7.5V.

"enable"

no

under

input

of

3)

will

always

keys

are

examination.

are operated

and

-7.5

volts, logic 0

volts

and

-15

volts.

LJLJ

!

~

NOR

gate will

the

three

depressed

<)

be

input

is a logic 0 (-15V)

input

be

a logic 0

to

between

is

--0

a square wave

nor

gates

(-15

volts)

the

left

of

any

(e.g.

the

(C)

ENABLE

(C)

a

0-------------,

KEYING

VOLTAGE

(B)

0------1

Enable (A) is a logic 0 Keying voltage is less than

The

release

is

fixed charge not

depressed keys are of

01-20

keying

3.2.3

(Refer

The T point supplies a voltage

Low

diode

to

the

drops

insures bus depressed.

3.2.4

(Refer

at

about

path

depressed,

is

(bus rod)

BASS

to

Lower

Note

drops

Lower

are

created

that

voltage

GATE

to

Lower

time

(decay

2.5

seconds,

is

provided to

shorten

01-20

always

of

Priority

higher

01-20

held

voltage

KEYING

Voicing

the

Bass Keying

to

the

Circuit

than

keyboard

using CR

will be biased ON regardless

wh

ich

decreases

DETECTOR

Voicing

only

when Enable

-7.5V

(logic 0). -

time

after

however,

through

VOLTAGE

the

release

are

off.

a full

diode

in

the

Schematic,

bass

of

which

the

keying

bus

rod

114,

030

CIRCUITS

Schematic,

01-20

ENABLE

)-------e

(C)

keys

are

released)

an

additional

for

those

time.

When

The

base

drop

above

reference

Reference

01-20

(P1·14).

as

generator.

sheet 3 of

Generator

of

is

at

least

voltage

The

andCR113.This

more

keys

sheet 3 of

(A)

and

the

keys

no

voltage

the

3.)

the

Bass

three

supplied

diode

of

the

are

3.)

When a key discharges transistors C42

through depression.) the

capacitor through a 3.3Mohm voltage gates

permits input provided volts no

lower

The

keying

COSMOS

is

(e.g.

the

of

that

and

keys

is

depressed,

a 1

uf

(01-020).

R7,

02

When a key

is

allowed

routed

the

B)

Z33B,

square

three

A)

the

are being

voltage

inverter

to

the

enable

sustain

(e.g. Key

and

resistor

an

4).

wave

input

keying

played).

is

(Z45-Z47)

-15 capacitor

CR63

is

released,

to

charge

input

Thus

to

be

nor

voltage

input

also

volts

from

through

2,

Pl-12

to

-15 the

back

(e.g.

R5).

of

the

three

the

keying

transmitted

gate

to

is

a logic 0

processed

and

the

discharges

volts

voltage

to

This

input

from

the

less

than

(indicating

through

a

nor

bus

rod

keying

on

key

on

0 volts

keying

nor

voltage

the

output

-7.5

gate

There

are

two

bus

rods

in

the

OMN

I,

one

for

the

lowest

20

keys,

one

for

the

upper

29

keys. Spl itti ng

the

bus

rod

in

this

manner

(Bass

AR)

to

be

developed

keys.

CR107 source through

is

volts

R130 across R differentiated

comparator

a

volts duration,

(Upper

for

CR107

depressed,

to

ground

on

key

130.

to

-15

Bass

the

upper

and

comparator

(Gate).

depression

The

by

Z52A

volts

longer

R130

voltage

C86

momentarily

and

for

separately

Gate

Detector)

bus

rod.

to

Z52B

The

results

so

back

multi-key

permits

-15

the

bus

switches

current

change

that

switches

again

depressions).

a bass

envelope

from

the

is

the

volts

is

suppl

rod.

When a key

from

drawn

in a voltage

across R

the

through

output

from

(10ms.

higher

voltage

ied

-15

drop

130

is

of

+15

typical

This

7

pulse

is

used

for

triggering (ADSR) not

3.2.5

(Refer

The Priority gated and when when a key C R1

Z51 A. amplitude couples and

022).

same (+7V).

rising edge clipping sawtooth down synthesizer

and signal. 8'

in for

provided

3.2.6

(Refer

The

clipping

key. waveforms +15

ground

off,

a

+15

about

and

to

bei

ng

played.

8'

AND

16'

to

Lower

single

square

Circuit

through a "VCA"

cn.

The

no

keys

are

is

depressed.

05

to

clip

As

the

AR

of

the

square

the

8'

Bass Waveshaping (R

The

base

This

of

the

off

the

waveform

by R

114

Bass signal.

resonated

The square half

(Z49).

the

WAVEFORM

Waveform

When

volts,

+15

little

volts since

+13.5

16'

wave

16' as

with

to

Lower

diodes

are

the

when

volts

extra

by Bass from

CR

Bass

the

the when

voltage

volts

discharge

BASS

Voicing

wave

(U2)

Bass AR

depressed

the

square

voltage

square

wave

and

means squarewave

falling edge

on

and R174

022

Waveshaping

106, R119

circuit.

the

8'

Voicing

Control

in

the

output produced. "hollow"

Waveform

the

op

by

NOTE: The CA339E (Z52) output more input, the bV external "pull

comparator. When the inverting

negative in voltage than the noninverting

output

is up"

is

This device

not

the

Envelope

sustain

WAVESHAPING

Schematic,

from

is

buffered

made

voltage

This

to

emitter

that

the

The

and

Z51 A

Bass

CONTROL

sets

Waveshaping

of

When

sound

the

switch

to

the

amp

itself.

capacitors

the

through

up

and

drops

voltage wave drops

wave

increases.

an

emitter

116,

of

021

only

will bias

of

the

emitter

and

sawtooth

used

accepts

and

divides

and

C80 Buffer (023

and

Schematic,

the

Z53

is 0 volts,

the

is

Enhancement

is

on.

output

cannot

is

open; the voltage

resistor circuits or networks.

a standard

specialized comparator (no feedback).

Generator

sheet 3 of

Bass

Low

Z51A

of

CR1

05, R112

(J11-8)

on

from

the

for

bias

produced.

an

is

to

-15

sets

the

output

ground,

follower

C78, R117,

are biased

differentiated

021

squarewave.

of

021 used

is

also

the

string

the

frequency

are

the

and

filtering

024).

sheet 3 of

point

circuits

output

CR1

07

when

the

supply

more

open collector

input

is

determined

op

amp;

on

keys

3.)

Note

and

0 volts

volts

bias

the

C77

AC

(021)

C79,

the

on,

thus

The

is

divided

for

the

altered

bass

buffered

"VCA"

are

of

the

for

each

sawtooth

of

Z53

J11-9

switch

provides

input

than

(-)

it

is a

of

3.)

(+)

The

Lower

Bus

Gate

Bus

circuitry.

R

150

trigger

The

Upper

the

base

drive

common each keying

from

maximum.

3.2.7

(Refer

The arrays circuits.

instrument. blocking section Bass Bass diodes.

The

are

routed

the

OMNI.

Detector

creates

on

key

and

of

circuit

discharge

key.

The

capacitor

running

4'

AN D 8'

to

Lower

outputs

(TDA470)

Formant

diodes

(first switches controls

4'

Poly

Bus

Trigger

circuit

CR

112

the

voltage

depression.

Lower

027

and

sustain

path

trigger

not

together

SUM

Voicing

of

the

are

filtering

CR101,

which

20

notes)

are

on.

are

on

Sum

(J11-16)

to

the

String

Detector

are

equivalent

is

the

lower

difference

Bus Triggers

supplied

bus.

for

the

pulse

being

played

when

Schematic,

five

4'

summed

is

CR102,

disable

when

the

Z48

supplies + 15

which

reverse biases

and

circuit

bus

for

are

via

026

The

sustain

keying

rapidly

to

the

release slider

and

8'

gating

in

the

provided

CR103

the

outputs

8'

or

8'

Poly

Synthesizer

and

to

the

voltage

discharges

and

16'

source,

the

lower

combined

to

the

bus

capacitors

prevent

sheet 3 of

transistor

4'

and

to

voice CR104 of

the

Synthesizer

volts

when

the

blocking

Sum

sections

Lower

Upper

bus

on

pulse

is

the

for

any

notes

is

3.)

8'

Sum

the

are

bass

the

(J11-2)

at

of

3.3 String Control Board

GENERAL: String Squelch Suppression

key

depressions,

times.

AR

is is is

is

to capacitors Voice

Selection.

3.3.1

(Refer

Z1

is a COSMOS pitch bass.

Z3A

to

the

Synthesizer

signals Pins 1, 2 and voices

AR

Envelope

and

The

AR

be

the

by

STRING

to

String

ranges:

sums

Phaser

and

for

are

selected.

The

String

forces

Squelch

same

tracking

VOICE

Control

4'

the

Board.

section

processing

13

disable

String

Generator, Voice the

yielding

as

the

Ouad

and

8'

four

Z2

to

Control

AR

Selection

AR

to

release

the

proper

forces

the release audio

level

SELECTION

Board

Schematic.)

Switch

be

the

which

polyphonic

pitch

ranges

(pins

3, 4 and

summed

through

String

Board

contains

Suppression,

circuits.

fully

stf{()g

release

time

of

from

selects

and

routes

5)

with

the

Phaser

AR

when

The

between

attack

time

of

all

the

String

the

8'

and

permits

the

Stri

Board.

no

the

AR

the

key

four

16'

them

the

ng

string

8

3.3.2

STRING

(Refer

to

String

The

String control VCA

integrating no

gate

o

volts rate released, through

When a key partially remains

3.3.3

(Refer

Z4B Voice Z4B

reverse charging

keys

signal

volts.

determined

monitors

(-15V)

voltage

on

the

are

Comparator

which

R37,

from

AR

to

Selection

and

supplies

as

biases

Control

AR

which

Synthesizer

capacitor

depressed.

on

Z4A

charges

the

-15

38,

is

depressed,

discharge

String

Control

the

circuit.

long

CR

faster

than

AR

Envelope

controls

and

pin 6

Z4A's

C15

by

the

volts

39.

C15

audio

it

to

as

an

11

and

the

AND

Board

Schematic)

Generator

Control

is

normally

When a key

changes

output

down

attack

is

allowed

Q3

momentarily

to 0 volts

key

depressions.

Board

Schematic.)

signal

from

C10

integrates

Z4C.

The

audio

signal

prevents

decay

AR

SUPPRESSION

the

gain

Board.

at 0 volts

is

from

changes

toward

slider.

Z3A

output

is

the

of

the

produces

of

the

String

C15

is

depressed,

-15

volts

to

-15

volts

When a key

to

discharge

turns

if

any

voltage

in

the

String

the

output

of

Z4C

present

AR

from

audio

which

signal.

the

when

the

to

-15 at

on

is

low

dis-

to

of

volts

to

+15

volts

when

the

output

volts.

This

then

reverses through the

a

is

When of repeats.

3.4.2

(Refer

The

attenuates

gain current ADSR (pin trimmer voltage

balancing

C R8

external through

3.4.3

(Refer

R45

direction

the

output

Z4A

switches

SYNTHESIZER

AMPLIFIER

to

Synthesizer

signals

of

the

VCA supplied output

3,

Z2)

via

(R

14)

changes

the

and R17

voltages

the

output

STRING

AMPLIFIER

to

Synthesizer

and

the

of

integration

of

back

from

is

to

is

connected

P12

minimizes on

current

provide

from

jack.

VOLTAGE

rate

Z4B

reaches

to

VOLTAGE

Control

Voltage

the

determined

the

differential

the

through

output

entering

Control

the

-15

10.

output

of

Z4B

direction

control

at

output

the

CONTROLLED

(R44)

the

output

-5

volts,

vo:ts

COI\JTROLLED

Board

Controlled

of

by

the

pair

to

the

The

control

effect

of

Z2A

and

protection

the

Board

and

Schematic)

the

Z2A,

control

the

OMN I

Schematic.)

reaches

of

current

and

of

the

output

the

cycle

Amplifier

VCF.

amount

B.

input

rejection

of

control

VCA

Z2B.

CR7,

to

prevent

circuits

+5

thus

Z4B.

The

of

The

by

3.3.4

ADSR

BLANKING

The

ADSR

circuit

prevents pedal

on

the

is

released.

blanking the

Synthesizer

ADSR

provides a pulse

Control

from

triggering

3.4 Synthesizer Control Board

GENERAL: the

Synthesizer Oscillator, String Mix

and

3.4.1

(R

efer

The

LFO output 20Hz. from hysteretic

The

Synthesizer Voice

Synthesizer

Voltage

Bass

LOW

to

in a Z4B current

Controlled

AR

Envelope

FREQUENCY

Synthesizer

produces a triangle

frequency

and

Cll

passing

switch

whose

Selection,

Voltage

Generator.

OSCILLATOR

Control

range

are

an

th

rough

output

Control

Controlled

Ampi

ifier,

and a square

from

integrator

switches

when

Board

Low

Board

about

R45.

to

the

board

the

contains

Frequency

Amplifier,

final

Output

Schematic.)

.1

which

Z4A

from

ADSR

which

foot

wave

Hz

to

charges

is

-15

The

String

Voltage circuit controlled instead

3.4.4

(Refer

The

are

volume

3.4.5

(Refer

The Polyphonic audio sizer output

a

gates selected.

as

the

by

of

the

OUTPUT

to

Synthesizer

output

mixed

four

of

by

of

the

SYNTHESIZER

to

Synthesizer

pitch

and

through

Control

of

the

(TDA470s)

Controlled

Synthesizer

the

String

ADSR.

MIX

the

Synthesizer

Z5A.

R23,

two

signals.

range

8',

16'

Z1

to

Board.

CR5

first

20

when

Control

the

VOICE

Control

push

Synthesizer

the

VCF

and

notes

the

Amplifier

VCA

AR

Envelope

VCA

Mix

SELECTION

buttons,

input

CR6

of

the

8'

and

except

Board

and

slider,

Board

4',8'

Bass

on

disable

polyphonic

16'

pitch

is

the

same

that

it

Generator

Schematic.)

String

VCA

controls

Schematic.)

Synthesizer

the

route

Synthe-

the

audio

ranges

the

tone

is

are

9

3.5

Synthesizer Board

GENERAL: Voltage Generator,

Output

3.5.1

VOLTAGE

(Refer

to

The

four

and

16'

input

of Voltage Octave The

filter octave) ZlB

sums

the

VCF. trimmer, audio

output

routed

3.5.2

(Refer

to

To

"start"

of

Z3A (Logic 1 to ADSR Pulse Drive. with

no

keys

depressed.

input

(Z4D

and

Z4D.

will

cause

(logic

O)

for

volts

The

Pulse Drive

and

pulses

is

depressed.

but

drops

released

The

output

(0 volts)

Pulse Drive pulse

The

Controlled

ADSR

Processing

Synthesizer

pitch Bass, are the

VCF

Controlled

and

has a

accepts

on

pin 4

and

inverts

R22,

prevents

(pin

to

the

Synthesizer

ADSR

GATING

Synthesizer

the

ADSR

must

Logic

Gating

to

The

keys

depressed,

The

Z4C

to 0 volts

as long as

to

logic 1

The

to

logic 0

to

prevent

of

but

drops

Synthesizer

Filter,

Gating

circuits.

CONTROLLED

Board

ranges,

change

first

summed

(pin

Filter.

manually negative to

the

control

10).

0).

set

up

Gate

The

13)

of negative

(logic

the

is

normally

ADS R

the

Z4A

to or

4'

1,

M1).

control

external CVR

The

VCA

Board

Envelope

from 0 volts

Two

this

(J12-7)

and

Gate

R·S

10

to

Gate

(about

blanking

when

ADSR

is,

logic 0

the

Board

contains

ADSR

and

the

Gate

FILTER

Schematic.)

and

8'

Polyphonic

and

voiced

M1

is a 4075

It has a

control

(Control

voltages

Schematic.)

signals

is

flip

1).

therefore,

cutoff

variable 0 (resonance).

voltages

the

filter

voltages

from

output

via J

12,

Generator,

must

condition:

is

-15

0 volts

supplied

flop transition change

Pin 10 will

on

J12-7

logic 0

-1

volt)

is

the

sustain

from

triggering.

(-15

ADSR

and

on

cutoff

which

Voltage

affecting

of

the

to

be

the

volts

with

one

to

made

on

from

remain

is

(about

every

normally

footswitch

normally volts)

blanking

Envelope

the

Low

of

(-1

5.

the

-15 sent

the

up

Z4C

-15

at 0 volts.

-13

time a key

during

Trigger

and

audio

24

volts/

point.

control

Reset)

VCF

output

volts

to Gate (Logic

or

more

Reset

of

volts

volts)

logic 1,

logic 1

pulse.

the

8'

Pass

dB/

the

and

0)

Z4C

at

the

second output

3.5.3

The negative and

ATTACK: high

R46 the from

3

integrating

DECAY

following

of

turn

Z3D.

is

8

0

falls

-7.5

low

CR4,

turns

and

reverse biased

goes

on 06 input

the

release setting sustain disabled occurs

3.6

is

Pulse Drive will

to

logic 0

ADSR

going

the

VCA.

to

low,

to

the

attack

ground.

and

applies

AND

ADSR

off

and

Z3C

below

volts)

applying

R38

on

R46

R51

and

CR5

RELEASE:

low

capacitor

to

ground.

of

follower

sustain

time.

on

footswitch

whenever

Phaser Board

GENERAL:

identical Low

Frequency

responsible

OMNI.

to

Envelope

DC

When

-15

non

inverting

mode,

04

Z2

directly

-15

capacitor

SUSTAIN:

the

voltage

and

establishes

which

by

parallel

and

the' the

and

the

for

approaches

R35

Z3D

threshold

output

-15 CR3

the

and

to

the

When

turns

C13

The

Z2

decay 05 front

ADSR

the

The

Phase

Oscillators.

the

momentarily

restart

the

Generator

voltage

the volts

to

output

is

input

is

off

follows

volts

through

C13

down.

on

capacitor

lowers

is a bistable

of

volts

from

thus

voltage

the

Sustain

capacitor

level

at

the

gate

on

06.

discharges

output

through

charge

and

07

panel

is

depressed.

Release

footswitch

Phaser

Shifters

orchestral

ADSR.

control

of

appl

ied

of

and

ZlA

-10

the

voltage

of

the

Z3C

holding

divider

C13

Z2

voltage

The

through

of

ZlA

R59

paths

permit

to

be

Control

Board

The

force

circuit

the

Z3A

changes

through C R2

follower

R45

is

disconnected

the

voltage

CR6,

R52

is a buffer

C13.

volts,

on

latch.

When

nand

changes

is

string

from

10

of

02

off.

consisting

Level.

discharges

3.

is

removed,

remaining

R53,

is

applied

thereby

from

the

release

overridden

Pulse

Drive

released.

contains

each

modulated

Phasers

effects

Z3A's

provides

VCF

cutoff

Z2.

During

on

to

charge

amplifier

The

output

02

begins

gate

(about

high

Z3

through

04

of

CR6

is

through

voltage

R50

to

preventing

affecting

~n

input

pulse

are

chiefly

of

from

and

to

13

of

13

to

now R45

now

Z3B

and

the

slider

the

which

three

by

the

a

is

10

Z3A Z4C

logic 1

until

will

has

after

change

changed

as

well.

from

logic 1

to

logic 1

and

Thus

Z4A

delays

the

Pulse Drive pulse has

to

after

the

logic 0

Z4A

ADSR

then

when

changes

"starting"

occurred,

to

A

3.6.1

(See Oscillator

LFO

Section

3.4.1

circuit.)

for

details

of

the

Low

Frequency

LFO

CONTROL

HFO

OUTPUT

-llUlJlJ1JIJ

DELAY

LINE

OUTPUT

SUMMMING

AMP

OUTPUT

The

three

Low

modulate

to

Pin 1 of Z 1 clipped

R

128

depressed,

3.6.2

(Refer

Voltage used

Z1 inherent 5 pf) as is to

o

Z104A should

oscillate discharges Z104B The 0 output oscillates.

0102 current the of 0101,102

placed

modulation varying 0102-0101.

3.6.3

(Refer

Z102

controlled

pins 2 and be out

the

.8msec.

to

approximate a sinewave.

in parallel

which

HIGH

to

Phaser

controlled

to

control

04B

is

capacitance

the

charged

maximum,

wh

the

by

ich resets

is

Z104B

after

and

converter

H.F.O. R116

H.F.O.

in

parallel

the

DELAY

to

Phaser

is

an

square

of

phase.

Phase

05A

FREOUENCY

a COSMOS

timing

0101. the 0 output

the

used

0101

to

when

depth

analog

by

12

waves

uJlJlJIJUlJ

ru1lnnJf~rl

Frequency

Shifters

is a triangle

with R127

slows

Board

High

delay

capacitor

Once

one

to

maintain

cease

power

of

Z104A

are a Iinear voltage

which (calibrate)

The

sinewave

vary

the

with

the

of

CIRCUITS

Board

delay

the

frequency

(typically

of

The

audio

Oscillators

varying

when

down

the

OSCILLATOR

Schematic)

Frequency

time

one

of

COSMOS

the

(pin 10)

shot.

oscillation,

up,

the 0 output

14

to

is

a logic 1 as long as

determines

sets

H.F.O. R118

chorus

frequency

Schematic.)

line

50KHz.).

the

same

input

the

delay

waveform

Z106B

the

chorus

LFO.

Oscillators

of

each phase

shot

wh

ich uses

gates

on

T2.

The

"capacitor"

changes

oscillation

or

not

start

Z104B

to

the

initial

from

the

LFO

exponentially.

to

increase

switch

of

change

whose

the

Pin 2

exact

the

is

delay

square

frequency,

device

--

are used

time

wh

ich

connects

switch

shifter.

(typically

"capacitor"

is

charged

to

logic

in

Z104B: begin of

Z104

oscillating.

Z104B

exponential

frequency

controls

R119

the

depth

selected

produced

time

wave

and

12

is

to

up

is

are

the

to

of

of by by

on

must

180

3,

is

the

outputs

Z103

is a latching

frequency

0).

3.6.4

(Refer

The by Synthesizer

3.7

3.7.1

Z1

approximately connected an

an

controls of tion of op emitter the

3.7.2

The +15

-15 of

through

increase,

then

lowering

3.7.3

R7 limit milliamps. to a maximum

pulses

FINAL

to

Phaser

outputs

Z1

and

Power Supply

+15VOLTSUPPLY

contains

op

amp.

emitter

the

power

of R11

the

op

amp

will

follower

power

-15

volt

supply

volt

supply

R14

and

R2. the

forces

the

SHORT

and

the

+15

are Pin

MIX

of

the

supplied

Board.

a voltage

+7

through

The

follower,

pass

supply

and R12

amp

in Z1

then

supply's

VOLT

volt

supply

R15

Should voltage

02

output

CIRCUIT

transistor

supply's

03

and

of

13

and

14.

flip

flop

which

from

Z104B

Board

three

volts

pin 5

output

transistor

change,

with

supply a correction

and

voltage

SUPPLY

through

is

at

the

is 0 volts.

the

on

to

supply

to

in Z1

R5

1000

to

Schematic.)

Phase

to

the

reference

to

pin 6

to

the

of

the

op

also

located

(01).

the

will

supply

the

voltage

pass

transistor

to

normal.

derives its

R14.

When

correct

Z2

is

output

pin 2

of

more

-15

volts.

PRODUCTION

connected current limit

the

milliamps.

converts

square

Shifters string

of

Z1.

noninverting

amp

Should

voltage

the

regulation

the voltage, referenced of

the

Z2 also increase.

current,

to a maximum

-15

the

waves

are

VCA

which

Th

is

voltage

is

connected

in

Z1, the

at

inverting

difference.

voltage

(01)

and

output

the

to 0 volts

minus

to

pins 2 and

supply's

high

(0

and

summed

on

the

supplies

input

which

output

the

junc-

input

The

to

the

bring

from

the

of

the

junction

supply

Z2

thereby

of

800

current

is of to

3

11

ARP Instruments Omni Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual