Lexicon PCM 42 Manuel utilisateur

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1

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pem

42

digital

delay

processor

Owner's

Manual

TABLE

OF

CONTENTS

SECTION

ONE

—

INTRODUCTION

1.0

Description

1.1

Precautions

SECTION

TWO

—

CONTROLS

&

INDICATORS

2.0

Introduction

2.1

Front

Panel

2.2

Rear

Panel

SECTION

THREE

—

INSTALLATION

3.0

Mounting

3.1

Power

Requirements

3.2

Audio

Signal

Connections

3.3.

Audio

Control

Jacks

3.4

Operating

Levels

3.5

Non-Audio

Remote

Control!

Functions

3.6

Clock

Output

3.7.

Voltage

Changeover

SECTION

FOUR

—

APPLICATIONS

4.0

Interconnecting

the

PCM

42

41

General

Application

Notes

and

Set-ups

4.1.0

Introduction

4.1.1

Echo

4.1.2

Double

Tracking

4.1.3

Flanging

4.1.4

Resonant

Effects

4.1.5

Vibrato

4.1.6

Pitch

Twisting

4.1.7

Stereo

Image

Placement

4.2

Special

Applications

of

Long

Delay

4.2.0

Introduction

CO

4.2.1

Layering

and

the

Infinite

Repeat

Mode

4.2.2

Looping

Techniques

for

Live

4.3

Programming

and

Using

the

Metronome/

Clock

Output

4.3.1

Setting

the

Clock

Rate

4.3.2

Interfacing

the

Clock

with

Rhythm

Machines

44

Interfacing

to

Other

Units

45

Delay

Lines

in

Distributed

Sound

Reinforcement

Systems

SECTION

FIVE

—

BLOCK

DIAGRAM

SECTION

SIX

—

SPECIFICATIONS

6.0

Test

Conditions

6.1

General

Performance

6.2

Interface

Information

6.3

Controls

and

Indicators

6.4

Power

and

Dimensions

SECTION

SEVEN

—

IN

CASE

OF

DIFFICULTY

7.1

General

7.2

Unit

Will

Not

Power

Up

7.3

Unit

Powers

Up,

Gives

Improper

Display

7.4

Unit

Powers

Up,

But

Will

Not

Pass

Audio

7.5

Returning

Units

For

Repair

7.6

Replacement

Parts

7.7

Limited

Waranty

1.0

DESCRIPTION

The

PCM

42

is

a

high-performance

digital

delay

line/

processor

that

features

up

to

2.4

seconds

of

high

quality

audio

delay,

expandable

to

4.8

seconds

with

optional

memory.

Delay

times

are

indicated

by

a

highly

accurate

numeric

display,

which

provides

rapid

tracking

of

ALL

changes

in

delay

time.

The

PCM

42

includes

ver-

satile

audio

patching

and

remote

control

facilities,

and

a

unique

synchronizing

clock

feature

that

allows

highly

musical

usage

of

the

very

long

delays

of

which

it

is

capable.

Long

repeat

loops

and

layering

effects

which

were

formerly

confined

to

the

studio

may

now

be

used

easily

and

reliably

on

stage.

The

42

provides

superior

audio

performance

through

Lexicon’s

proprietary

method

of

analog-to-digital

encoding.

An

increased

sampling

rate

gives

wider

band-

width

without

aliasing

effects.

In

addition,

a

new

“‘soft-

knee”

limiting

circuit

eliminates

the

unpleasant

distortion

that

most

digital

circuits

generate

when

overloaded.

The

PCM

42’s

excellent

sonic

quality,

unique

features,

light

weight,

flexibility

and

ease

of

use

make

it

the

perfect

choice

either

on

stage

or

in

the

studio.

1.1

PRECAUTIONS

Although

the

PCM

42

is

a

very

well-behaved

device,

precautions

consistent

with

good

practice

for

any

piece

of

audio

gear

should

be

observed

as

a

matter

of

course.

SECTION

ONE

INTRODUCTION

Before

turning

the

PCM

42

on

or

off,

it

is

advisable

to

lower

the

volume

on

your

power

amplifier

or

monitoring

system

to

avoid

undesirable

transients.

Never

connect

power

sources

or

audio

power

amplifiers

directly

into

ANY

of

the

PCM

42’s

phone

jacks.

The

PCM

42’s

inputs

are

designed

for

line

level

signals.

If

a

guitar

amplifier

is

used

as

a

signal

input,

then

a

suitable

attenuator

pad

must

be

used

to

lower

the

level

of

the

feed

to

the

PCM

42.

To

prevent

fire

or

shock,

never

operate

the

PCM

42

in

the

rain

or

in

exposed

wet

locations.

Please

read

Section

Three

UNSTALLATION)

of

this

manual

before

operating

the

PCM

42.

WARNING

ALL

SERVICING

OF

THE

PCM

42

SHOULD

BE

PERFORMED

BY

QUALIFIED

SERVICE

PER-

SONNEL.

THERE

ARE

HAZARDOUS

VOLTAGES

LOCATED

UNDER

BOTH

THE

TOP

AND

BOTTOM

COVERS

OF

THE

UNIT.

TO

AVOID

ELECTRICAL

SHOCK,

REMOVE

THE

POWER

CORD

BEFORE

REMOVING

COVERS.

SERVICING

PROCEDURES

CON-

SISTENT

WITH

GOOD

SAFETY

PRACTICE

SHOULD

BE

USED

AT

ALL

TIMES.

SECTION

TWO

CONTROLS

&

INDICATORS

2.0

INTRODUCTION

ly

describes

the

PCI

ee

A

a

AA

aicators.

More

cet

d

applications

is

conta

2.1

FRONT

PANEL

E

F

GH

J

M

P

VW

Figure

2.1

—

PCM

42

Front

Panel

When

the

button

is

out,

the

unit

is

set

for

the

short

Re

nEROROOM

lore

range

(O0-1200

ms

standard,

0-2400

ms

with

memory

op-

The

HEADROOM

display

monitors

the

audio

level

tion)

and

16

kHz

bandwidth.

Pushing

the

button

selects

after

the

INPUT

LEVEL

and

FEEDBACK

controls.

The

the

long

range

(0-2400

ms

standard,

0-4800

ms

with

display

has

5

LEDs

which

indicate

peak

levels

relative

to

memory

option)

with

6

kHz

bandwidth,

illuminating

the

converter

overload.

The

input

stage

operates

normally

6

kHz

LED

(Fig.

2.1,

Q).

The

numeric

delay

display

up

to

3

dB

below

the

absolute

limit,

where

a

5:1

com-

always

indicates

the

actual

delay

time.

pression

ratio

comes

into

play.

At

0

dB,

the

input

stage

limits,

and

further

increases

in

input

level

will

produce

C.

INPUT

LEVEL

no

additional

input

to

the

digitizer.

Even

extreme

input

levels

produce

only

a

soft

distortion,

rather

than

clip-

ping.

The

Headroom

Display

follows

the

compressor/

limiter,

indicating

the

audio

level

actually

seen

by

the

analog-to-digital

converter;

thus

it

becomes

non-linear

with

respect

to

the

input

signal

when

the

O-dB

LED

is

lit.

The

INPUT

LEVEL

control

adjusts

the

input

gain

for

proper

matching

of

the

PCM

42’s

sensitivity

to

the

input

signal.

Set

this

control

so

the

HEADROOM

display

occasionally

indicates

0

dB

on

program

peaks,

with

average

levels

at

about

-12

dB

(in

the

green

zone).

NOTE:

A

rear

panel

switch

provides

an

additional

BE

PEEE

TENGE

20

dB

of

gain

for

low

level

inputs,

such

as

the

output

of

The

DELAY

X2

switch

determines

whether

the

PCM

an

instrument

pickup.

For

details,

see

Section

2.2,

42

is

in

the

short

(X1)

or

the

long

(X2)

time

delay

range.

paragraph

“|”.

D.

FEEDBACK

cloc

k\

wise

feeds

the

Be

WECUY

FILTER

Engaging

the

HI

CUT

ne

OONG

low-pass

f

Nee

i

back

path.

This

is

useft

aiat

ing

room

am

bien

CE

ness

of

highl

ly

reson

Engag

reverses

fed

bac

back

signal

ats

phase

c

Bich

acter

and

is

typically

used

for

resonant

fenuingss

sounds:

G.

DLY

INV

Engaging

the

DLY

INV

(Delay

Invert)

button

reverses

the

polarity

of

the

delayed

sound

which

ts

fed

to

the

OQUTPUT

MIX

control

(Fig.

2.7,

1).

H.

BYPASS

LED

In

Bypass

mode,

the

Delay

signal

is

cut

out

of

the

mix

at

the

MAIN

OUTPUT,

and

all

input

to

the

delay

line

is

cut

off.

This

LED

is

illuminated

when

the

BYPASS

is

ac-

tivated

by

the

optional

footswitch

or

an

external

logic

signal.

|.

OUTPUT

MIX

The

OUTPUT

MIX

control

establishes

the

ratio

of

direct

to

delayed

sound

in

the

PCM

42

MAIN

OUTPUT.

Full

counterclockwise

position

(toward

INPUT)

provides

100%

direct

sound

from

the

input

preamplifier.

Full

clockwise

position

provides

100%

delayed

sound.

The

control

is

detented

in

center

position,

where

the

blend

of

signals

is

equal.

This

point

is

calibrated

for

maximum

notch

depth

during

flanging.

J.

©

RPT

The

INFINITE

RPT

pushbutton

causes

the

PCM

42

to

capture

the

sound

in

the

delay

memory

at

the

first

clock

pulse

after

the

button

is

pressed

and

repeat

that

seg-

ment

continuously

until

the

button

is

pressed

again

The

repeat

mode

uses

the

entire

delay

memory

—

the

length

of

the

captured

segment

is

independent

of

the

delay

tap

selected

with

the

UP

and

DOWN

pushbut-

tons,

but

changes

with

the

settings

of

the

MANUAL

VCO-SWEEP

control

and

the

DELAY

X2

pushbutton.

ise

ae

the

infinite

repeat

mode

is

enabled

not

at

nt

the

button

is

pressed,

but

at

the

first

clock

cree

(as

Ow

He

the

flashing

CLK

LED

at

the

right

of

he

di

/

that

time.

To

See

rapid

entry

into

this

rate

To

a

sma

delay

time

lene

section

K,

below!

il

fraction

of

the

total

TI

ill

not

power

up

in

repeat

mode.

If

the

INFINITE

RPT

button

is

“IN”

at

time

of

power

up,

the

‘ll

not

enter

the

:

Ae

eat

mode

until

the

pushbutton

is

released

ane

press

selected

throu

to

the

rear

pane

ee

Repeat

mode

can

also

be

ry-contact

switch

attached

REP

EAT

jack

(Fig.

2.2,

D}.

K.

SET-MODE

The

SET-MODE

slide

sv

vitch

determines

the

function

of

the

display

and

the

U

P

ag

d

DOWN

pushbuttons.

In

normal

operation,

this

switc

“

s

set

to

DLY

(left)

and

the

display

shows

the

delay

time

in

milliseconds,

while

the

pushbuttons

increment

and

decrement

the

delay

tap

selection.

With

the

SET-MODE

switch

in

the

CLK

(right)

posi-

tion,

the

UP

and

DOWN

pushbuttons

change

the

rate

of

the

flashing

CLK

LED

and

of

the

pulses

appearing

at

the

CLOCK

output.

In

this

mode,

the

display

indicates

the

period

of

the

clock

as

a

fraction

of

the

maximum

delay

time

(as

determined

by

the

DELAY

X2

and

the

MANUAL

VCO-SWEEP

settings).

The

numerator

of

the

fraction

is

on

the

left,

the

denominator

on

the

right.

The

DOWN

button

cycles

the

numerator

through

odd

in-

tegers

1,

3,

5, 7,

and

9.

The

UP

pushbutton

causes

the

denominator

of

the

fraction

to

cycle

through

binary

values

1,

2,

4,

16,

32,

and

64.

L.

DOWN

BUTTON

—

DELAY/CLOCK

The

DOWN

pushbutton

decrements

the

delay

tap

value

or

the

denominator

of

the

CLOCK

output

ratio,

as

described

in

paragraph

‘‘K’’

above.

With

the

SET-

MODE

switch

in

DLY,

a

short

press

and

release

of

the

button

will

decrease

the

delay

time

by

one

increment.

If

the

button

is

held

in,

the

selection

will

decrease

approx-

imately

once

per

second.

To

move

rapidly

to

a

new

set-

ting,

the

UP

button

may

be

pressed

while

continuing

to

hold

DOWN.

When

UP

is

released,

the

increment

rate

reverts

to

once

per

second.

M.

UP

BUTTON

—

DELAY/CLOCK

The

UP

pushbutton

increments

the

delay

tap

value

or

the

numerator

of

the

clock

ratio

as

described

above

in

paragraphs

“’K"’

and

“L’’.

As

with

DOWN,

the

rate

of

increase

of

the

delay

time

may

be

accelerated

by

press-

ing

DOWN

while

holding

UP.

Thus,

the

direction

of

change

is

determined

by

which

button

is

pressed

first,

while

the

rapid

mode

is

enabled

by

the

opposite

button.

N.

DELAY

DISPLAY

When

the

SET-MODE

switch

is

in

the

DELAY

posi-

tion,

the

DELAY

DISPLAY

gives

a

precise

4-digit

display

of

the

actual

Gelars

ime

in

milliseconds.

With

the

SET-MODE

switch

at

CLOCK,

it

shows

display

of

the

clo

ae

eee

{see

seca

K

above).

The

delay

time

disp

is

accurate

and

updates

itself

very

quickly,

stewines

it

to

track

all

sweep

functions

as

fast

as

the

eye

can

follow.

O.

CLK

LED

The

CLK

LED

flashes

in

synchrony

with

the

CLOCK

UTPUT

on

the

rear

panel.

The

rate

at

which

the

la

amp

he

is

determined

by

the

fraction

programmed

v

os

SET-MODE,

DOWN

and

UP,

coupled

with

the

settin

of

the

VCO-SWEEP

controls.

To

determine

the

exact

period

of

the

CLOCK,

step

the

delay

tap

value

upward

with

UP

until

the

display

ceases

to

increment,

indicating

maximum

delay

time.

(Use

the

fast-forward

function

described

in

paragraphs

K

and

L.)

Note

the

delay

time,

and

then

switch

SET-

MODE

to

CLOCK

and

read

the

display

as

a

fraction,

with

the

numerator

on

the

left

and

the

denominator

on

the

right.

The

clock

period

is

equal

to

the

delay

time

times

the

clock

fraction.

Note

that

if

DEPTH

is

not

set

to

QO,

or

an

external

modulation

is

present,

the

clock

rate

will

not

be

stable.

P.

co

LED

The

INFINITY

LED

is

illuminated

whenever

the

repeat

mode

is

selected

by

the

INFINITE

RPT

pushbutton

or

the

corresponding

footswitch

jack.

Q.

6

kHz

LED

The

6

kHz

LED

lights

when

the

long

delay

mode

is

selected

by

DELAY

X2,

indicating

a

reduction

in

band-

width

to

6

kHz

and

a

doubling

of

the

available

range

of

delay.

R.

MANUAL

VCO-SWEEP

The

MANUAL

VCO-SWEEP

control

provides

con-

tinuous,

smooth

control

of

delay

times

over

a

range

of

3

to

1

by

modifying

the

sampling

rate.

This

control

func-

tions

as

a,manual

modulation

for

flange,

chorus

and

pitch

twisting

effects,

and

for

access

to

very

long

delay

times.

S.

DEPTH

The

DEPTH

control

adjusts

the

amount

of

internal

modulation

of

the

VCO,

affecting

the

depth

of

sweep

r

or

flange,

chorus

and

pitch-twisting.

When

DEPTH

is

set

at

“O"',

the

internal

sweep

Is

inactive.

As

the

DEPTH

control

.

advanced

clockwise

toward

‘'10",

the

range

of

the

sweep

increases

to

a

maximum

clock

ratio

of

3:1.

The

DEPTH

control

interacts

with

the

MANUAL

¥CO-SWEEP

control

(Fig.

2.1-R).

The

MANUAL

con-

trol

has

its

maximum

effect

with

the

DEPTH

at

0",

and

no

effect

with

the

DEPTH

control

at

10".

T.

WAVEFORM

The

WAVEFORM

control

selects

the

modulation:

type

of

VCO

1.

Full

counterclockwise

rotation

selects

sinusoidal

modulation:

the

delay

time

smoothly

increases

and

decreases

at

a

speed

governed

by

the

RATE

setting.

2.

Setting

the

control

at

the

center

detent

selects

envelope-follower

modulation:

the

delay

time

changes

in

response

to

the

level

of

the

input

signal.

3.

Full

clockwise

rotation

selects

square-wave

modulation:

the

delay

time

jumps

instantaneously

up

and

down

according

to

the

setting

of

the

RATE

control.

4.

Intermediate

positions

of

the

control

blend

either

sinusoidal

or

square-wave

modulation

with

envelope-follower

modulation.

U.

RATE

The

RATE

control

adjusts

the

low-frequency

oscillator

(LFO)

that

controls

the

frequency

of

the

sine-

or

square-wave

modulation.

With

the

WAVEFORM

control

in

the

center

(envelope-follower)

position,

the

RATE

control

will

have

no

effect.

V.

RATE

LED

The

RATE

LED

flashes

on

and

off

to

indicate

the

rate

of

the

LFO

and

to

allow

playing

in

synchronization

with

the

delay

sweep.

W.

POWER

SWITCH

This

latching

pushbutton

turns

the

AC

power

on

and

off.

On

power-up,

the

delay

time

is

automatically

set

to

O

ms,

the

infinite-repeat

function

is

turned

OFF,

and

the

clock

ratio

is

set

to

a

value

of

1/2.

All

other

switch

and

control

settings

remain

as

they

had

previously

been

set.

2.2

REAR

PANEL

Figure

2.2

—

PCM

42

REAR

PANEL

A.

POWER

CONNECTOR

The

POWER

connector

accepts

standard

IEC

power

cords.

Before

plugging

in

the

AC

cord

and

applying

power,

check

the

adjacent

d

plate

to

ensure

that

the

set

operating

voltage

matches

that

of

the

AC

mains.

B.

VCO

REMOTE

JACK

The

VCO

input

jack

allows

remote

operation

of

the

MANUAL

VCO-SWEEP

control

by

means

of

a

foot

con-

troller

(optional),

or

an

externa!

control

voltage

(range

O

to

+10

Volts;

O

Volts

=

maximum

delay,

+

10

Volts

=

minimum,

linear

over

a

range

of

3:1).

The

VCO

jack

accepts

a

standard

1/4”

phone

plug

for

control

voltages,

or

a

stereo

tip/ring/sleeve

plug

when

used

with

the

optional

foot

controller

(Lexicon

A-CP-41

Foot

Pedal).

When

the

plug

is

inserted,

the

MANUAL

VCO-

SWEEP

is

bypassed

and

has

no

effect.

C.

BYPASS

SWITCH

JACK

The

BYPASS

function

provides

a

means

of

quickly

switching

the

delay

signal

out

of

the

MAIN

OUTPUT

mix,

while

at

the

same

time

killing

the

feed

to

the

delay

circuitry

itself.

The

BYPASS

jack

accepts

a

1/4”

phone

plug

and

the

BYPASS

is

activated

when

the

tip

of

the

plug

is

shorted

to

the

sleeve,

or

when

a

TTL

logic

‘0"

is

present

at

the

tip.

D.

co

REPEAT

SWITCH

JACK

The

INFINITE

REPEAT

function

is

activated

by

a

momentary

switch

closure

or

the

falling

edge

of

a

TTL

compatible

clock

pulse.

The

unit

remains

in

repeat

mode

until

another

closure

or

pulse

arrives

OR

the

front

panel

INFINITE

REPEAT

pushbutton

(Fig.

2.1,

J)

is

released

from

a

depressed

position.

The

BYPASS

func-

tion

and

the

INFINITE

REPEAT

mode

may

be

controlled

with

a

single

Lexicon

A-FS-41

Dual

Footswitch

Assembly,

or

any

combination

of

one

latching

(BYPASS)

and

one

momentary-contact

(INFINITE

REPEAT)

switch.

E.

CLOCK

OUTPUT

JACK

The

CLOCK

OUTPUT

jack

provides

a

TTL-compat-

ible

square

wave

output

suitable

for

clocking

many

automatic

rhythmic

devices

and

sequential

controllers.

The

rate

of

the

clock

is

a

fraction

of

memory

Capacity

at

the

current

sampling

rate,

programmable

from

the

front

panel.

This

allows

synchronization

of

external

devices

to

the

delay

period.

(See

Sections

3.6

and

4.3.2.)

F.

DELAY

OUTPUT

JACK

The

DELAY

OUTPUT

is

an

unbalanced

tip/sleeve

jack

carrying

the

output

of

the

delay

line

at

line

level,

unmixed

with

any

of

the

direct

signal.

(See

Sections

3.2

and

4.4.)

G.

DIRECT

OUTPUT

JACK

The

DIRECT

OUTPUT

is

an

unbalanced

tip,’sleeve

jack

which

carries

only

the

input

signal

after

preampli-

fication.

This

signal

is

at

system

line

level.

H.

INPUT

JACK

The

INPUT

jack

is

a

balanced,

differential

input

which

accepts

a

1/4”

tip/ring/sleeve

phone

plug;

unbalanced

sources

can

be

accommodated

by

simply

substituting

a

tip/sleeve

phone

plug.

A

high

input

impedance

allows

the

PCM

42

to

interface

with

either

low

or

high

im-

pedance

sources.

|.

GAIN

SWITCH

The

GAIN

Switch

matches

the

PCM

42's

‘nput

sen-

sitivity

to

the

signal

source.

Engaging

the

switch

in-

creases

sensitivity

by

20

dB

for

sources

such

as

electric

pickups,

high-output

microphones,

and

some

electronic

instruments.

J.

FEEDBACK

CONTROL

JACK

The

FEEDBACK

CONTROL

jack

provides

two

distinct

functions.

When

used

with

a

tip/ring/sleeve

plug

and

a

n

onan

41)

or

any

potentiometer,

the

o

the

ee

remotely.

it

can

uxillary

input

which

is

combined

without

gain

conte

(nominal

line

ions

3.3

and

4.2.2

A

ss

main

|

=

=

ae)

eS

See

Secti

NOTE:

THIS

FUNCTION

IS

INDEPENDENT

OF

THE

F

ai

NT

PANEL

FEEDBACK

CONTROL.

RUNAWAY

DBACK

CAN

RESULT

IF

BOTH

CONTROLS

ARE

RAISED

AT

THE

SAME

TIME.

K.

MIX

CONTROL

JACK

Like

the

FEEDBACK

CONTROL,

the

MIX

CONTROL

jack

{

ai

35

dual

functions.

With

a

potentiometer

o

foot

pedal,

the

user

can

raise

and

lower

the

volume

the

delayed

signal

in

the

MAIN

OUTPUT

mix.

ae

delay

effects

can

be

faded

in

and

out

at

will.

This

jack

can

also

be

used

to

inject

an

external

signal

into

the

out-

put

mix.

(See

Sections

3.3

and

4.2.2.)

L.

MAIN

OUTPUT

The

MAIN

OUTPUT

is

an

unbalanced

tip/sleeve

jack

whose

signal

level

is

determined

by

the

adjacent

con-

trol.

It

carries

the

blend

of

di

rect

and

processed

signal

which

is

set

with

the

front

panel

OUTPUT

MIX

control

(Fig.

2.1,

I).

f

M.

OUTPUT

LEVEL

The

OUTPUT

LEVEL

control

adjusts

the

MAIN

OUT-

PUT

level

from

its

maximum

of

+179

dBV

(9

V

rms)

down

to

full

attenuation.

This

control

should

be

ad-

justed

to

provide

the

maximum

level

to

the

monitor

system,

amplifier

or

console

without

clipping

its

input

stage.

ADEQU

TOM

AND

,

whether

or

not

it

's

k-mounted,

This

is

of

particular

importance

if

the

s

mounted

above

power

ampli

er

heat

gener:

2Ng

gear.

Since

the

PCM

42

processes

low-level

audio

signals,

if

iS

advisable

to

locate

it

away

from

strong

elec-

tromagnetic

fields,

such

as

those

generated

by

power

transformers,

motors,

fluorescent

ballasts,

etc.

3.1

POWER

REQUIREMENTS

The

PCM

42

is

set

at

the

factory

to

operate

at

either

100,

115,

or

230

volts

(50

-

60

Hz).

The

factory-set

voltage

is

indicated

on

the

rear

panel

next

to

the

power

receptacle.

The

maximum

power

required

is

20

watts.

Units

set

for

100

or

115

volts

are

fused

at

1/4

ampere,

230-volt

units

at

1/8

ampere.

THE

OPERATING

VOLTAGE

SHOULD

NOT

BE

CHANGED

EXCEPT

BY

A

QUALIFIED

SERVICE

TECHNICIAN.

The

PCM

42's

power

cord

has

a

standard

three-pin

IEC

connector

to

simplify

adaptation

to

power

sources

in

various

countries,

and

to

provide

chassis-to-mains

grounding

according

to

accepted

safety

standards.

SECTION

THREE

INSTALLATION

3.2

AUDIO

SIGNAL

CONNECTIONS

r

stereo

(or

>}

Plugs

for

Input

ad

this

Ssupsection

fo

or

foot

pedal

cor

é

e

proper

cable

for

each

ensure

that

YOU

are

function.

IGE

UTD

ruSsed

WA

g

(Tip

=

signal

high,

|

Ring

=

signal

iow,

Sleeve

=

shield

ground).

it

can

aiso

be

used

with

unbalanced

input

sources

when

fed

by

a

T/S

phone

plug

(Tip.

=

signal

high,

Sleeve

=

sana

ow!

shi

ield).

This

creates

a

traditional

single-ended

inpu

NOTE:

if

a

T/R/S

plug

is

used

with

a

source,

be

sure

to

short

the

ring

and

sl

together.

single-ended

eeve

terminals

OUTPUTS

The

MAIN,

DIRECT

and

DELAY

audio

outputs

(Fig.

2.2,

L,

G

and

F)

are

unbalanced

(single-ended),

and

are

intended

for

use

with

a

T/S

phone

plug.

Load

im-

pedances

of

5

kilohms

or

higher

can

be

driven

to

full

levels;

loads

as

low

as

600

ohms

may

be

driven

without

loss

of

signal

quality,

although

the

output

level

will

be

reduced

slightly.

lf

the

PCM

42

is

used

to

drive

microphone

level

inputs

from

the

DIRECT

or

DELAY

outputs,

it

will

be

necessary

to

insert

a

20-

or

30-dB

pad

at

the

input

to

the

driven

device.

The

MAIN

OUTPUT

has

its

own

level

control.

3.3

AUDIO

CONTROL

JACKS

The

PCM

42

has

two

audio

control

jacks

which

are

wired

in

T/R/S

configuration.

In

both

of

these,

the

sleeve

iS

a

common

ground,

and

a

single-ended,

buf-

fered

delay

output

appears

on

the

ring.

The

tips

of

the

jacks

are

connected

to

different

input

patch

points

in

the

PCM

42.

FEEDBACK

CONTROL

JACK

(Fig.

2.2,

J)

The

tip

terminal

of

this

eo

is

connected

to

a

patch

point

that

is

mixed

with

the

main

INPUT.

The

input

ac-

cepts

single-ended,

lin

Bega

ee

from

a

source

of

any

impedance.

Connecting

a

Lexicon

A-CP-41

foot

pedal

to

this

jack

places

the

foot

pedal’s

internal

poten-

tiometer

between

the

ring

and

the

tip,

mixing

the

delay

output

with

the

main

input

and

thus

allowing

remote

control

of

feedback

or

regeneration.

Since

the

delay-only

output

on

the

ring

is

bu

two-way

T/S

phone

plug

may

be

inserted

in

thi

mix

any

other

line-level

signal

with

the

mai

i

without

compromising

the

delayed

signal.

A

T/RY

plug

with

connections

to

the

ring

and

sleeve

only

will

permit

the

use

of

either

audio

control

jack

as

a

separate

delay-only

output.

="

et

¢

Pe

a

mA&ow

NOTE:

The

feedback

loop

enabled

by

this

control

jack

iS

separate

from,

and

operates

in

parallel

with,

the

front

panel

FEEDBACK

control

and

its

associated

HI-

CUT

and

FB

INV

switches.

If

the

two

controls

are

used

simultaneously,

runaway

feedback

(howling)

can

occur.

When

using

the

FEEDBACK

CONTROL

jack

with

the

foot

pedal,

turn

the

front

panel

FEEDBACK

control

to

0.

MIX

CONTROL

JACK

(Fig.

2.2,

K)

Inserting

a

phone

plug

into

this

jack

interrupts

the

connection

of

the

delay

signal

to

the

OUTPUT

MIX

con-

trol

on

the

front

panel.

A

foot

pedal

plugged

into

this

jack

allows

the

performer

to

fade

the

delay

effects

as

desired

from

zero

up

to

the

setting

of

the

OUTPUT

MIX

control.

This

jack

may

also

be

used

to

insert

other

signal

processors,

ane

as

equalizers,

into

the

path

of

the

delayed

signal.

The

input

accepts

single-ended,

line-

level

audio

from

a

source

of

any

impedance.

3.4

OPERATING

LEVELS

INPUT

LEVELS

The

PCM

42

can

handie

a

wide

variety

of

input

sources

including

microphones,

electric

instruments,

mixer

outputs

and

so

on.

The

high-impedance

delay

line

input

will

operate

equally

well

with

low-

or

high-

impedance

sources.

It

is

important,

however,

to

set

the

10

input

sensitivity

So

that

the

unit

can

acco

full

dynamic

range

of

the

source

i

aye

e;

~

signa

ai/noise

ratio

and

mmodate

the

with

£

To

match

the

PCM

42's

sensiti

the

source,

ae

must

first

set

rear

panel.

Push

the

button

in

(selecting

20

a

of

extra

ae

cee

when

using

sour

ue

with

peak

levels

ranging

from

-23

dBV

to

0

dBV

(0.07

V

to

1.0

V

rms).

This

in-

cludes

electric

pickups,

high

output

mireropuene

coe

level

mixer

outputs,

and

some

electronic

instr

pices

instrument

preamplifier

outputs.

ivity

to

input

the

20

dB

GAIN

switch

on

the

O

I

noul

Ihe

button

should

be

out

sources

with

peak

levels

rangir

70V

to

9.0

Vrms}.

This

output

Ss,

some

puts

and

some

(unity

gain}

when

using

ng

from

-3

dBV

to

+19

includes

high

level

mixer

e

electronic

instrument/preamplifier

out-

direct

box

outputs.

With

the

appropriate

switch

position

engaged,

adjust

the

front

panel

INPUT

LEVEL

control

for

peak

HEADROOM

displays

of

0

dB,

with

average

levels

around

-12

dB.

vel

is

unknown,

Start

at

the

0

dB

out),

and

adjust

the

INPUT

i

to

otk

g

the

HEADROOM

display

within

desi

red

paniaes

f

the

gain

is

insufficient

to

achieve

peaks

of

-6

dB

with

Ae

INPUT LEVEL

at

maximum,

turn

dov

he

INPUT

LEVEL

and

engage

the

+20

dB

positio

re

signal

ley

:

iE

itimm

fA:

SATIN

Eee?

1

(Dutton

WARNING

NEVER

CONNECT

THE

PCM

42

INPUT

DIRECTLY

TO

POWER

SOURCES,

IM-

PROPERLY

ISOLATED

AC/DC

DEVICES,

OR

POWER

AMPLIFIERS.

DISREGARDING

THESE

PRECAUTIONS

CAN

LEAD

TO

ELEC-

TRICAL

SHOCK,

AND

MAY

DO

SEVERE

DAMAGE

TO

THE

PCM

42.

MAIN

OUTPUT

LEVEL

The

PCM

42

MAIN

OUTPUT

is

designed

to

drive

loads

of

5

kilohm

or

higher

impedance

at

a

level

of

9

V

rms

(+18

dBV).

It

is

possible

to

drive

impedances

as

low

as

600

ohms,

although

maximum

output

level

is

reduced

to

about

5

V

rms

(+

14

dBV).

NOTE:

Do

not

use-the

INPUT

LEVEL

control

to

set

output

level.

Once

the

proper

input

level

is

established,

the

rear

panel

OUTPUT

LEVEL

control

can

be

used

to

adjust

the

MAIN

OUTPUT

level

for

a

wide

range

of

devices.

In

general,

best

signal-to-noise

performance

results

at

set-

tings

of

mid-scale

or

higher.