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INSTRUCTION

MANUAL

It is

essential

you

rend

this

instroction

booklet

carefully

before

installing

your

high

fidelity

system.

You

have

invested

in

an

extremely

fine

clectronic

instru-

ment

into

which

many

excellent

enginecring

developments

have

been

incorpo-

rated,

and

cach

is

important

for

the

proper

operation

of

your

system.

This

booklet

has

heen

written

in

simple

nontechnical

language

and

if

you

will

take

time

to

Tead

it

frst

before

doing

anything

eke,

you

will

find

it

simple

to

obtain

optimum

performance

from

your

Harman-Kardon

Model

A-224

Stereephonic

Amplifier.

Be

sure

to

keep

this

booklet

available

at

all

times.

lt

contains

indispensable

tecn

nical

and

service

information,

A

ifr

Mie

Horwtew-Karcen

Serea

Spanked,

fit

paar

atinaere

of

caperd

nered

T

Š,

GENERAL

DESCRIPTION

The

A-224

stereophonie

amplifier

is

extremely

versatile

and

may

be

used

in

any

of

the

following

ways.

1—Stereophonic

amplifier

with

12

watts

of

audio

in

each

channel.

2—Monaural

amplifier

with

24

watts

of

audio,

48

watt

peaks.

3—Stereophonic

conversion

amplifier

utilizing

your

present

high

fidelity

amplifier

or

combination

unit

for

the

second

channel.

UNPACKING

After

unpacking

the

Trio,

inspect

it

carefully

for

signs

of

transit

damage.

The

unit

was

subjected

to

many

inspections

and

tests

prior

to

final

packing,

and

it

therefore

should

be

in

perfect

condition.

If

damage

is

visible,

notify

your

dealer

at

once,

If

the

unit

was

shipped

to

you,

notify

the

transportation

company

without

delay.

Check

the

contents

of

the

carton

thoroughly

and

inspect

the

folds

of

the

packing

material

before

discarding

it.

Your

package

should

contain

the

following

ibems:

1

Trio,

Model

A-224

Stereophonie

Amplifier-Preamplifier.

1

Instruction

Booklet

1

Warranty

Card

1

Mounting

‘Template,

WARRANTY

POLICY

We

urge

you

te

completely

fill

in

your

warranty

card

amd

mail

it

te

the

fac-

tery

without

delay

te

protect

your

rights

under

warranty.

The

warranty

ecards

are

carefully

filed

for

reference

and

should

you

require

information

on

the

use

of

this

high

fidelity

unit,

or

repair

service,

we

will

be

able

to

immediately

identify

your

set

and

reply

quickly,

NOTE:

It

is

necessary

to

receive

factory

authorization

before

returning

a

get

for

warranty

repair

cither

to

the

factory

or

to

an

authorized

station.

Repairs

are

to

be

returned

on

an

Express

Propaid

basis,

A

letter

describing

the

exact

diffi-

culty

mast

be

enclosed

with

the

unit

WARRANTY

We

warrant

each

Trio

Model

A-224

to

be

free

from

defects

in

material

and

workmanship

under

normal

use

and

service,

and

in

accordance

with

the

canili-

tions

herein

below

set

forth,

for

a

period

of

1

year

from

date

of

delivery

to

the

original

purchaser,

aml

agree

to

replace

or

repair

any

part

or

parts,

with

the

exception

of

tubes

which

are

under

the

manufacturer's

90

day

warranty,

reburned

to

us

within

said

1

year,

with

transportation

prepaid

and

which

our

examination

shall

disclose

to

our

satisfaction

to

have

been

thus

defective.

This

warranty

does

net

include

free

labor,

nor

is it

applicable

to

any

instrument

which

shall

have

been

repaired

or

altered

in

any

way

so as

in

our

judgment

to

affect

its

stability

or

reliability

nor

which

has

been

subject

to

neglect,

misuse,

abuse,

negligence

or

accident

nor

whieh

has

had

the

serial

number

altered,

effaced,

or

removed.

Neither

shall

this

warranty

apply

to

any

instrament

which

has

heen

connected

otherwise

than

in

accordance

with

instructions

furnished

by

us.

This

warranty

is

expressly

in

Heu

of

all

other

warranties,

express

or

implied,

and

of

all

other

obligations

or

lability

on

our

part,

and

we

neither

assume

nor

authorize

any

representative

or

other

person

to

assume

for

us

any

other

liability

in

connection

with

the

sale

of

this

instrument.

USING

THE

MODEL

A-224

AS

A

STEREOPHONIC

AMPLIFIER

INSTALLATION

PROCEDURE

Ventilation:

The

unit

is

well

ventilated

in

itsclf,

but

sufficient

space

must

be

allowed

around

it

to

permit

proper

air

flow.

Install

the

amplifier

in

a

manner

to

allow

for

unrestricted

circulation.

Do

not

pkice

books

or

other

objects

on

the

cage

or

in

the

immediate

vicinity

of

the

instrument.

Reducing

the

air

flow

will

result

in

sharply

reduced

component

and

tube

life.

Power

Requirements:

Plug

the

AC

cord

into

any

outlet

furnishing

LIT

volts

50

or

60

cycle

AC

oir-

rent.

The

voltage

may

vary

between

15

and

125

volts.

Two

AC

convenience

outlets

are

located

on

the

rear

of

the

instrument.

Auxiliary

apima

{tape

deck,

record

player,

additional

amplifier)

may

be

plugged

inte

these

outlets

and

will

be

controlled

by

the

on/olf

switeh

located

on

the

A-224,

REAR

PANEL

CONNECTIONS

=

LEFT

SArARcAS

EHT

giha

FAR

|

Deae

|

2Qaeae

e@

|

a

è

ü

if

IË

5 E

E

Wf

Tare

(js)

oH

et

AEAN

PÄHEL

HOOTL

Ane

Connecting

Your

Speakers:

Your

two

speakers

should

be

matched

if

possible

to

obtain

optimum

results

and

should

be

placed

approximately

&

to

15

feet

apart

a

one

wall

of

your

listening

room.

Corner

placement

is

also

quite

acceptable.

Facing

the

speakers

straight

out

or

slanting

them

slightly

will

depend

om

your

room

size,

scoustle

effect

and

where

you

will

be

seated

for

listening.

It

may

be

mecessary

to

experi-

ment

with

speaker

placement

tatil

best

results

are

obtained.

Use

any

type

wire

to

commect

your

speakers,

Lamp

cord

is

excellent

and

muy

be

eusily

dressed

around

the

molding

for

an

inconspicuous

and

neat

installation.

Normal

Stereo

Speoker

Arrangement:

Connect

one

lead

from

the

left

speaker

te

the

16

ohm

terminal

on

the

LEFT

SPEAKER

output

strip

and

the

other

lead

to

the

A

or

B

terminal

on

the

same

strip.

Now

connect

one

of

the

leads

from

the

right

speaker

to

the

LA

ohm

term-

inal

on

the

RIGHT

SPEAKER

output

strip

and

the

other

lead

to

the

A

or

B

terminal

on

the

same

strip.

NOTE:

A

and

B

terminals

on

both

SPEAKER

output

strips

are

strapped

together

at

the

factory

and

should

be

allowed

to

remain

strapped

for

this

method

of

steren

speaker

connection.

(Sec

Dingram

A)

The

output

terminals

nsed

should

be

those

marked

with

the

same

impedance

as

the

speakers,

The

above

illustration

is

for

16

ohm

speakers,

If

you

are

using

§

ohm

speakers

connect

to

the

4

ohm

SPEAKER

output

terminals

rather

than

to

the

16

ohm

terminals.

The

two

SPEAKER

SELECTOR

switches

located

on

the

front

panel

are

za

P

for

this

method

of

connection,

and

their

setting

is

therefore

not

critica

IMPORTANT:

For

all

methods

of

stereo

operation,

the

POWER

PARAL-

LEL

switch

mounted

on

the

front

chassis

support

apron

to

the

left

of

the

pilot

light

must

remain

in

the

“SEPARATE”

position,

The

cage

(if

used)

must

be,

removed

to

provide

acoess

to

this

switch.

E

NORMAL

STENE

SPEAKER

HOOK

UP

Diagram

A

Two

Independent

Stereo

Speaker

Systems:

The

Model

A-224

stereo

amplifier

incorporates

a

unique

switching

arrange-

ment

enabling

the

user

to

operate

two

independent

stereo

speaker

systems

bo-

cated

in

different

rooms.

Remove

the

shorting

bar

between

A

and

B

terminals

on

both

SPEAKER

out:

put

strips.

Connect

a

lead

from

the

left

speaker

in

System

A

to

the

16

ohm

term-

inal

on

the

LEFT

SPEAKER

output

strip

and

another

lead

from

this

speaker

to

the

A

terminal

on

the

same

strip.

Connect

the

right

speaker

in

System

A

to

terminals

16

and

A

on

the

RIGHT

SPEAKER

output

strip.

This

complete

System

A

installation,

E

To

install

System

B

connect

a

lead

from

the

left

speaker

to

the

16

ohm

terminal

on

the

LEFT

SPEAKER

output

strip

and

another

lend

to

the

B

term-

inal

on

the

same

strip.

Now

connect

the

right

speaker

in

System

B

to

the

16

and

B

terminals

on

the

RIGHT

SPEAKER

output

strip.

This

completes

System

B

in-

stallation,

(See

Diagram

1)

The

above

illustration

is

for

16

chm

speakers,

IF

you

are

using

8

ohm

speak-

ers

connect

to

the

8

ohm

terminals

on

the

SPEAKER

OUTPUT

strip

rather

than

to

the

16,

If

one

pair

of

speakers

is

8

ohms

and

the

other

pair

16

ohms,

then

connect

appropriately.

For

this

type

of

installation

the

SPEAKER

SELECTOR

switches

located

on

the

front

panel

are

operative.

See

Stereo

Operating

Instructions.

IMPORTANT:

The

POWER

PARALLEL

switch

located

on

the

front

chassis

support

apron

to

the

left

of

the

pilot

light

must

remain

in

the

"SEPA-

BATE”

position.

The

cage

(if

used)

must

be

removed

to

provide

access

to

this

awitch,

Army

ATRAPA

HOO

uP OF

TEÒ

INDEPENDENT

STEREO

SPEAKER SYSTEMS

Diagram

B

No

further

connections

need

be

mule

to

your

old

monaural

amplifier.

Pro-

gram

sources

such

as

tuner,

tape,

phonograph,

ete.

are

connected

to

the

appro-

priate

receptacles

on

the

A-234

as

deseribed

under

stereo

installation.

OPERATING

YOUR

MODEL

A-224

AS

A

CONVERSION

AMPLIFIER

Operation

of

the

model

A-234

as

a

stereo

conversion

amplifier

is

identical

with

ils

operation

as

a

normal

stereo

amplifier.

The

controls

of

the

old

monaural

amplifier,

now

being

used

as

one

channel

of

your

new

stereo

system,

must

be

properly

set,

however,

amd

then

loft

permanently

in

that

setting.

Sa

the

tone

controls

amd

contour

switch

to

Hat,

the

rumble

and

scratch

filter

switches

to

off,

and

the

funetion

selector

to

AUX

or

TUNER,

depending

on

which

input

receptacle

was

used

for

connecting

to

the

A-224.

Set

the

VOLUME

control

on

your

old

amplifier

to

minimum

and

mljust

the

BALANCE

Control

on

your

Model

A-224

to

the

mid-point.

Play

a

stereo

rec-

ord

of

tape

and

turn

the

LOUDNESS

Control

on

your

A-224

up

te

a

mormal

lis-

tening

volume.

The

left

channel

will

be

inoperative

since

the

volume

control

on

your

old

amplifier

is

set

at

minimum,

Now

slowly

rotate

the

volume

control

on

this

amplifier

until

the

loudness

of

the

two

channels

is

equal,

Allow

the

volume:

control

on

your

second

amplifier

to

remain

in

this

pesition

permanently.

ADJUSTMENTS

Output

Balance:

Individual

OUTPUT

BALANCE,

controls

for

Left

and

Hight

channels

are

located

between

the

EL-84

output

tubes.

These

controls

balance

the

two

output

tubes

of

each

channel

for

lowest

power

hum

and

distortion.

Adjustment

is

quite

simple:

With

the

amplifier

turned

on

for

a

sufficient

length

af

time

to

be

thor-

oughly

warmed

up,

tum

the

LOUDNESS

control

to

minimum.

Now,

while

lis-

tening

carefully

to

the

left

speaker,

adjust

the

LEFT

OUTPUT

BALANCE

con-

trol

for

minimum

hum,

‘Then,

while

dstening

to

the

right

speaker

only,

adjust

the

RIGHT

OUTPUT

BALANCE

control

for

minimum

hum.

Due

to

the

ex-

tremely

low

hum

level

of

the

A-224,

this

is

best

done

at

a

time

when

the

room

is

vory

quiet.

The

setting

for

minimum

hum

is

attained

only

when

the

two

power

tubes

have been

exactly

balanced,

and

this

is

the

comelition

for

absolute

minimum

distortion.

Hum

Adjustment:

One

HUM

ADJUST-HIGH

LEVEL

control

and

one

HUM

ADJUST-LOW

LEVEL

control

are

located

on

the

chassis

behind

the

electolytic

condenser

and

in

front

of

the

LAUT

tube.

Each

operates

simultaneously

to

adjust

both

left

and

right

channels.

To

adjust

for

minimum

hum,

set

the

FUNCTION

switch

to

TUNER,

tum

the

tuner

olf

(if

porinactes’)

and

turn

the

LOUDNESS

control

full

on.

While

listen-

ing

to

either

s

neaker,

adjust

the

HIGH

LEVEL

hum

enatrol

for

minivan

Wir.,

Now

set

the

FUNCTION

switch

to

the

TAPE-LO

position,

and

set

the

LOW

LEVEL

hum

control

for

minimum

hom.

System

Hum

or

Noise:

in

any

high

fidelity

installation,

hum

may

be

couse

by

the

interconnection

af

a

record

changer,

tuner

and

amplifier,

as

a

result

of

the

cables

and

different

groumds.

A

1

way

to

climinate

this

problem

is

to

first

disconnect

everything

but

the

speakers

from

the

amplifier,

and

listen

for

hum,

Lf

the

hum

persists,

make

the

hum

and

balance

adjustments

described

above.

Try

reversing

the

ampli-

fer

power

plug,

Now

plug

in

the

record

player.

Hf

hum

appears,

try

reversing

the

record

player

power

plug,

and

try

connecting

a

wire

from

the

record

player

chassis

to

the

amplifier

chassis.

In

this

way,

connect

the

tuner,

tape

deck

and

other

de-

vices

in

ture.

Note

that

hum

may

be

picked

up

by

defective

interconnecting

cables,

and

by

interconnecting

cables

running

too

close

to

power

cables.

Connecting

Your

Tumir:

The

FM

output

of

your

Harman-Kardon

stereo

tuner

should

be

connected

to

the

LEFT

TUNER

input

jack

on

the

HIGH

LEVEL

INPUT

strip

located

om

the

rear

panel,

The

AM

output

should

be

connected

to

the

RIGHT

HIGH

LEVEL

INPUT

jack.

The

same

method

of

installation

applies

if

you

are

using

separate

FM

and

AM

tuners.

Plug

the

AC

line

cord

of

your

tuner

into

one

of

the

AC

com-

venience

outhets

located

om

the

rear

panel

of

the

Model

A-224

amplifier,

Connecting

Your

Stereo

Record

Player:

A

stereo

cartridge

is

essentially

two

cartridges

in

ome

amil

uses

two

ouput

connecting

plugs.

If

yeu

are

using

a

low

level

maguetic

cartridge

phig

one

output

lead

into

the

LEFT

LOW

LEVEL

INPUT

locatel

on

the

lower

left

rear

of

the

chassis,

and

the

other

plug

into

the

RIGHT

LOW

LEVEL

INPUT

jack.

Both

PHONO,

TAPE

switches

located

directly

above

the

LOW

LEVEL

INPUT

jacks

must

be

placed

in

the

up

or

“PHONO”

position.

Stereo

crystal

or

ceramic

cartridges

may

also

be

used

with

this

amplifier.

They

must

be

plugged

into

the

LEFT

and

RIGHT

FHONO-HI

jacks

located

on

the

HIGH

LEVEL

INPUT

strip

on

the

rear

panel.

Plug

the

AC

line

cord

of

your

record

player

into

one

of

the

AC

convenience

outlets

located

on

the

rear

panel

of

the

Model

A-224

amplifier,

Connecting

Your

Stereo

Tape

Player:

A

steresphonic

tape

deck

utilizes

two

pliyback

heads.

Each

head

has

its

own

output

pug.

Connect

one

plug

to

the

LEFT

LOW

LEVEL

INPUT

jack

located

on

the

lower

rear

of

the

Daan:

and

the

other

apn

ping

to

the

RIGHT

LOW

LEVEL

INPUT

jack.

Place

both

PHONO/TAPE

switches

located

directly

above

the

LOW

LEVEL

INPUT

jacks

down,

in

the

“TAPE”

position.

Since

the

Model

A-224

has

anly

one

pair

of

low

level

input

receptacles.

for

stereo

use,

cither

a

magnetic

cartridge

or

a

tape

head

may

be

plugged

in,

It

beth

types

of

program

sources

are

desired,

it is

suggested

a

ceramic

cartridge

be

used

instead

of

a

magnetic

type.

The

tape

head

can

then

be

plugged

inte

the

two

LOW

LEVEL

INPUT

jacks

and

the

ceramic

cartridge

can

be

plugged

into

the

two

PHONO-HI

jacks,

Connecting

Your

Stereo

Tape

Recorder:

Since

most

sterco

tape

recorders

have

their

own

preamplifiers,

it

is

mot

de-

sirable

to

plig

the

autput

of

the

recorder

into

the

LOW

LEVEL

INPUT.

This

might

canse

overloading

of

the

input

stage.

Connect

one

of

the

output

plugs

into

the

TAPE-HI/AUX

jack

on

the

RIGHT

HIGH

LEVEL

INPUT

strip

and

the

other

inte

the

TAPE-HI/AUX

jack

on

the

LEFT

HIGH

LEVEL

INPUT

strip.

Connecting

Your

Tape

Recorder

To

Make

A

Recording:

Provision

is

made

on

your

Model

A-224

to

permit

the

recording

of

any

pro-

gram

material.

Connect

the

left

input

of

your

stereo

tape

recorder

to

the

ra-

ceptacle

marked

LEFT

TAPE

OUT

on

the

rear

panel

and

the

right

input

of

your

stereo

tape

recorder

to

the

receptacle

marked

RIGHT

TAPE

OUT.

To

con-

nect

a

monaural

tape

recorder,

connect

its

input

to

either

LEFT

or

RIGHT

TAPE

OUT

receptacle,

If

the

program

source

you

desire

to

record

is

plugged

inte

the

left

preamplifier

channel,

use

the

LEFT

TAPE

OUT

jack,

and

if

it

is

plugged

inte

the

right

preamplifier

channel,

use

the

RIGHT

TAPE

OUT

jack.

This

will

enable

you

to

make

a

recording

with

the

proper

recording

equalization

as

determined

by

your

recorder,

while

simultancously

monitoring

the

program

with

the

proper

tone

control,

contour

and

lowdness

setting.

Connecting

Your

Record

Player:

Any

type

of

record

player

may

be

used

with

this

amplifier,

IF

your

player

uses

a

low

level

magnetic

cartridge

plug

it

into

either

the

LEFT

or

RIGHT

LOW

LEVEL

INPUT.

Sct the

appropriate

PHONO,

TAPE

switch

located

on

the

rear

panel

to

the

“PHONO”

position.

IF

you

are

using

a

monaural

ceramic

or

crystal

cartridge

plug

it

inte

either

the

LEFT

or

RIGHT

PHONO-HLI

input.

Connecting

Your

Tape

Player:

Connect

your

monaural

tape

deck

to

one

of

the

LOW

LEVEL

INPUT

acks

on

the

rear

panel.

IF

your

magnetic

cartridge

is

connected

to

the

LEFT

OW

LEVEL

INPUT,

connect

the

tape

deck

to

the

RIGHT

LOW

LEVEL

IN-

FUT,

or

viceversa.

The

PHONO’

TAPE

EQUALIZATION

switch

correspond-

ing

to

the

LOW

LEVEL

INPUT

used

for

the

tape

deck

must

be

in

the

TAPE

position

for

proper

tone

equalization.

Connecting

Your

Tape

Recorder:

Since

most

monaural

tape

recorders

have

their

own

preamplifier,

it

is

not

desirable

to

plug

the

output

of

the

recorder

into

the

LOW

LEVEL

INPUT

jack,

This

might

cause

overloading

of

the

input

stage.

Conmect

the

recorder

output

plug

to

either

LEFT

or

RIGHT

TAPE-AI/AUX

jack

on

the

rear

panel.

Connecting

Your

Tape

Recorder

To

Make

A

Recording:

Provision

is

mide

on

your

Model

A-224

ampliber

to

permit

the

recording

of

any

program

material,

Connect

the

input

of

your

monaural

tape

recorder

to

either

the

LEFT

or

RIGHT

TAPE

OUT

receptacle

located

on

the

rear

panel.

TF

the

program

source

you

desire

to

record

is

plugged

into

the

left

preamplifier

channel,

use

the

LEFT

TAPE

OUT

jack

and

if

it

is

plugged

into

the

right

pre-

amplifier

channel,

use

the

RIGHT

TAPE

OUT

jack.

This

will

enable

you

to

make

a

recording

with

the

proper

recording

equalization

as

determined

by

your

recorder,

while

simultaneoush

monitoring

the

program

with

the

proper

tone

contrel,

contour

amd

boudness

setting-

Connecting

Auxiliary

Monaural

Equipment:

A

TV

toner

or

other

similar

device

with

high

output

levels

may

be

con-

nected

to

either

the

LEFT

or

RIGHT

TAPE-HI/AUX

jock

on

the

rear

panel.

OPERATING

THE

MODEL

4-224

AS

A

MONAURAL

AMPLIFIER

The

Model

A-234

incorporates

the

following

front

panel

controls.

Viewing

the

instrument

from

left

to

right

you

will

note

a

TREBLE

Control

(on‘olf

switch

is

incorporated

in

this

control),

BASS

Control.

LOUDNESS

Control,

BALANCE

Control,

MODE

Switch

and

FUNCTION

Switch.

On

the

upper

left

section

of

the

front

panel

you

will

note

two

SPEAKER

SELECTOR

Switches

and

on

the

upper

right

section

a

CONTOUR

Switch

and

RUMBLE

FILTER

Switch,

TECHNICAL

EXPLANATION

OF

THE

CONTROLS

Bass

and

Treble:

These

controls

provide

the

full

range

of

tonal

adjustment

necessary

for

high

fidelity

listening.

These

controls

can

either

boost

or

cut

the

bass

and

treble

tomes

of

your

monaural

system.

The

controls

should

be

set

in

accordance

with

your

hearing

preference,

speaker

characteristics

and

room

acoustics.

Loudness

Contra:

This

control

adjusts

the

volume

lovel

of

any

program

material

fed

into

your

high

fidelity

system.

Its

effect

can

be

modified

by

the

CONTOUR

Switch.

OPERATING

THE

MODEL

A-224

AS

A

STEREOPHONIC

AMPLIFIER

Every

control

on

a

well

designed

and

honestly

considered

high

fidelity

in-

strument

has

a

specific

useful

function,

related

to

each

of

the

other

benm

$

Af

brief

explanatory

note

on

the

relationship

of

the

various

front

panel

controls

will

`

doubtless

prove

useful

in

organizing

and

clarifying

them

for

you.

The

Model

A-234

incorporates

the

following

front

panel

contrels,

Viewin

the

instrument

from

left

to

right

you

will

note

a

TREBLE

control

(on/‘oll

switch

is

incorporated

in

this

control),

BASS

control,

LOUDNESS

contr,

BALANCE

eontral,

MODE

switch

and

FUNCTION

switch.

On

the

upper

left

section

of

the

front

panel

you

will

note

two

SPEAKER

SELECTOR

switches

and

on

the

upper

right

section

a

CONTOUR

switch

and

RUMBLE

FILTER

switch.

TECHNICAL

EXPLANATION

OF

THE

CONTROLS

Since

a

stereo

amplifier

is

actually

two

amplifiers

in

one,

the

number

of

operating

controls

menali

normally

be

doubled.

This

would

make

operation

un-

necessarily

cumbersome.

For

convenience

the

duplicate

controls

are

mechanically

tied

zelian,

or

ganged,

to

be

operated

hy

ane

knob.

Boss

and

Treble:

The

BASS

and

TREBLE

controls

on

the

Model

A-224

provide

the

full

range

of

tonal

adjustment

necessary

for

high

fidelity

listening

These

controls

can

either

boost

or

ent

the

bass

and

treble

tones

of

the

stereo

system.

The

controls

ahould

be

set

in

accordance

with your

hearing

preference,

speaker

characteristics

and

room

acoustics.

Loudness

Control:

This

control

adjusts

the

volume

level

of

any

program

material

fed

into

your

stereo

system.

Its

effect

can

be

modified

by

the

CONTOUR

switch.

{

Contour

Switch:

One

of

the

Limitations

of

human

hearing

is

its

tendency

to

lose

sensitivity

to

the

very

low

pitched

sounds,

as

the

program

sound

level

is

reduced.

It

is

this

characteristic

(known

as

the

Fletcher-Munson

effect)

which

causes

one

to

play

music

programs

at

high

listening

level

in

order

to

experience

the

full

rich

tone

available

from

fine

modern

recordings.

The

Harman-Kardon

CONTOUR

switch

compensates

for

the

Fletcher-Munson

effect

thos

eliminating

high

listening

levels

as

a

requisite

for

full

enjoyment

of

reproduced

music,

For

low

level

listening

throw

the

CONTOUR

switch

located

on

the

front

panel

to

the

“ON”

position.

You

will

note

how

the

low

frequencies

become

more

apparent

while

the

volume

level

remains

unchanged.

Balance

Control:

The

nature

of

stereo

reproduction

is

such

that

it

requires

two

identical

channels

ta

attain

the

highest

degree

of

faithfulness

and

spatial

distribution.

Any

variation

in

the

efficiency

of

one

channel

as

compared

to

the

other

will

distur

this

relationship.

Since

there

may

be

slight

differences

between

the

two

speakers,

tape

heads,

ete,

the

A-224

includes

a

control

te

balance

one

channel

against

the

other,

Sufficient

range

is

covered

by

this

control

to

permit

rebalancing

of

the

overall

system

even

in

cases

where

major

unbalance

exists.

It

is

entirely

to

be

ex-

pected

that

this

control

will

be

set

anywhere

within

its

range

to

attain

system

balance.

When

the

BALANCE

control

is

properly

set,

the

apparent

sound

source

will

lie

in

a

broad

area

between

the

two

speakers.

When

the

BALANCE

control

is

rotated

to

the

right

the

sound

will

move

to

the

right

and

when

the

control

is

;

rotated

to

the

left,

the

sound

will

move

to

the

left.

Mode

Switch:

The

MODE

switch

selects

between

stereo

operation,

where

a

stereo

program

source

is

available,

and

monaural

operation

utilizing

the

full

power

of

both

chan-

nels

and

both

speakers

when

the

program

source

is

onai

a

USING

THE

MODEL

A-224

AS

A

CONVERSION

AMPLIFIER

FOR

STEREO

If

you

mow own

a

basic

amplifier,

or an

amplifier-preamplifier,

you

may

utilize

the

model

A224

for

the

second

channel

and

control

the

entire

sherco

sys-

tem

with

the

A-224

preamplifier,

For

this

application

the

model

A-224

is

con-

nected

in

the

manner

described

below.

INSTALLATION

PROCEDURE

Connecting

Your

Speakers:

Your

two

speakers

should

be

matched

if

possible

to

obtain

optimum

results

and

should

be

placed

8

to

15

feet

apart

against

one

wall

of

your

listening

room,

Comer

placement

is

also

quite

acecptable.

Facing

the

speakers

straight

out

or

slanting

them

slightly,

will

depend

on

your

room

size,

acoustic

effect

and

where

you

will

be

seated

for

listening.

It

may

be

necessary

to

experiment

with

speaker

placement

until

best

results

are

obtained.

Use

any

type

wire

to

connect

your

speakers.

Lamp

cord

is

excellent

and

miay

be

easily

dressed

around

the

molding

for

an

inconspicuous

and

neat

installation.

Speaker

Connection

For

Conversion

Arrangement:

Set

the

POWER

PARALLEL

Switch

located

on

the

front

chassis

support

apron

to

the

left

of

the

pilot

light

to

the

“PARALLEL”

position

and

strap

the

appropriate

Speaker

Output

terminals

together.

IMPORTANT:

Whenever

the

POWER

PARALLEL

Switch

is

in

the

“PARALLEL”

position,

the

Speaker

Oul-

put

terminals

must

be

strapped

together,

and

conversely

whenever

the

Speaker

Üutput

terminals

are

strapped

together,

the

POWER

PARALLEL

Swibely

must

be

in

the

“PARALLEL”

position.

Connect

Speaker

A

(refer

to

Diagram

E)

to

either

$2

ohm

terminal

on

the:

Speaker

Output

strip

and

the

other

lead

to

either

A

terminal.

Now

tie

the

two

32

ohm

terminals

together.

The

A

and

B

terminals

on

both

output

strips

have

been

strapped

together

at

the

factory,

and

should

be

left

that

way,

IF

you

are

using

an

&

ohm

speaker,

tie

the

two

16

ohm

terminals

together

instead

of

the

32

ohm

terminals

as

cescrited,

The

SPEAKER

SELECTOR

Switch

on

the

front

panel

may

be

placed

in

any

position

since

it

is

inoperative

for

this

method

of

installation.

Connect

Speaker

B

te

the

“G"

and

16

ohm

speaker

terminals

on

your

other

monaural

amplifier,

SREAKES

HOON

UF

POM

STERED

COVES

Diogram

E

Connecting

Both

Amplifiers

For

Stereo

Operation:

Connect

a

shielded

lead

not

longer

than

3

or

4

feet

between

the

LEFT

PREAMP

OUT

jack

on

the

rear

of

the

A-224

and

the

Aux

or

Tuner

input

on

your

other

amplifier,

Connect

the

AC

power

cord

from

your

monaural

amplifier

to

the

AC

cem-

venience

outlet

on

the

rear

of

the

Model

A-234.

The

on,‘off

switch

on

the

A-224

will

now

control

the

power

for

both

amplifiers,

Contour

Switch:

One

of

the

limitations

of

human

hearing

is

its

tendency

to

lose

sensitivity

to

the

very

low

pitched

sounds,

as

the

program

sound

level

is

reduced,

It

is

this

characteristic

(known

as

the

Fletcher-Munson

effect)

which

causes

one

to

play

music

programs

at

high

listening

level

in

order

to

experience

the

full

rich

tone:

available

from

fine

modern

recordings.

The

Harman-Kardon

Ci

INTOUR

Switch

compensates

fer

the

Fletcher-Munsen

effect,

thus

climinating

high

listening

levels

ag

a

requisite

for

full

enjoyment

of

reproduced

musie,

For

low

level

listening

throw

the

CONTOUR

Switch

located

on

the

front

panel

to

the

“ON”

position.

You

will

note

how

the

low

frequencies

become

more

apparent

while

the

volume

level

remains

unchanged.

Balance

Contred:

This

control

has

no

function

in

monaural

listening

and

should

be

left

in

the

center

position.

If

rotated

to

either

extreme

position,

it

would

completely

shut

off

the

preamplifier

on

that

side.

Mode

Switch:

The

only

application

for

this

switch

in

monaural

operation

is

to

select

he-

tween

the

twa

preamplifiers.

This

allows

for

double

the

usual

number

of

input

jacks

found

on

ordinary

monaural

amplifiers.

The

STEREO

NORMAL.

and

MONAURAL

RIGHT

positions

are

identically

connected and

will

activate

the

Right

preamplifier,

therefore

awitching

on

all

program

material

connected

to

this

preamplifier.

STEREO

REVERSE

and

MONAURAL

LEFT

are

identically

con-

nected

and

will

activate

the

Left

p

amplifier,

For

simplicity,

it is

suggested

to

use

only

the

MONAURAL

RIGHT

and

MONAURAL

LEFT

positions

on

the

MODE

Switch

for

monaural

operation.

Switch

to

MONAURAL

RIGHT

or

MONAURAL

LEFT

as

a

function

of

the

preamplifier

you

wish

to

use,

Funetion

Switch:

The

FUNCTION

Switch

selects

the

desired

type

of

program

source

and

has

four

positions.

TAPE-LO/PHONO-LO

selects

the

program

source

plugged

into

the

LOW

LEVEL

INPUTS

which

may

be

either

tape

or

magnetic

phono,

The

next

position,

PHONO-HI,

selects

either

of

the

two

PHONG-HL

inputs.

The

TUNER

position

selects

your

monaural

tuner

for

operation

and

the

AUX/

TAPE-

HI

selects

your

tape

recorder

or

other

auxiliary

monaural

equipment.

Speaker

Selector

Switch:

In

a

monaural

installation

where

more

than

one

set

of

speakers

are

installed!

{for

example:

one

speaker

in

the

living

room

and

another

in

the

den)

selection

between

the

two

speakers

is

made

by

operating

the

SPEAKER

SELECTOR

switch

on

the

front

panel.

To

operate

Speaker

A

(located

in

your

living

room)

set

the

Left

SPEAKER

SELECTOR

Switch

located

on

the

front

panel

to

“A”,

and

the

other

SPEAKER

SELECTOR

Switch

to

“ONE”.

To

select

Speaker

E

flocated

in

another

room),

set

the

SPEAKER

SELECTOR

Switch

to

“B"

and

the

right

SPEAKER

SE-

LECTOR

Switch

to

“ONE”,

To

operate

both

speakers

simultaneously,

set

the

Left

SPEAKER

SELECTOR

Switch

to

either

“A”

or

“BY and

set

the

right

SPEAKER

SELECTOR

Switch

to

“ALL”.

Rumble

Filter:

At

times,

record

changers,

records

and

even

some

turntables

produce

an

ob-

jectional

low

frequency

signal

that

is

strong

enough

to

be

introduced

into

the

sensitive

playback

system.

Known

as

“Rumble”,

this

unlesirable

signal

can

be

climinated

by

the

special

RUMBLE

FILTER

Switeh

incorporated

in

the

Model

A-234.

Whenever

rumblo

is

encountered,

set

the

switch

to

“ON”.