Harman Kardon The Trio User manual

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
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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”.