Sansui AU 777 A Owners Manual

Page 1

OPERATING INSTRUCTIONS
& SERVICE MANUAL

SOLID-STATE STEREO AMPLIFIER

SANSUI All-777A

SANSUI ELECTRIC COMPANY LIMITED

Page 2

Thank you for selecting the Sansui AU-777A Solid State Stereo-
phonic Amplifier, an excellent choice that will become more ap
parent after years of rich stereo listening.

Sansui is known throughout the world for the unsurpassed quality
of its audio equipment line, be it a preAmain amplifier, 3 multiplex
stereo receiver, a speaker system, a turntable or a stereo head-
phone set, and takes the greatest efforts to merit and maintain
this reputation.

The AU-777A is no exception. Not a single detail has been
overlooked in bringing this unit to you in perfect operating condi-
tion.

This manual has been prepared to aid you in keeping the AU-
777A working perfectly. Please read the contents of this manual
carefully before Installing or operating the amplifier.

You will then be able to enjoy the world's highest standards of
sound reproduction to the fullest.

CONTENTS

SWITCHES AND CONTROLS ............................ 3, 4, 5, 6
OPERATIONS .................................................... 7, 8
#SPEAKER CONNECTION
-RECORD PLAYING
-MICROPHONE
OPERATIONS .................................................... 9, 10
-RADIO RECEPTION
-TAPE PLAYBACK
-TAPE RECORDING

ELECTORONIC CROSSOVER SYSTEM .................. 11, 12
THREE-CHANNEL STEREO .................................... 13
MAINTENANCE .......................................... 14,15, 16
SPECIFICATIONS .................................................. 17
CHARACTERISTICS .............................................. 18
TROUBLESHOOTING CHART .............................. 19, 20
CUSTOM MOUNTING ........................................ 21, 22
PARTS LAYOUT .................................................. 23
BLOCK AND LEVEL DIAGRAM ................................ 24
ALIGNMENT
-TEST POINT .................................................. 25
-MAIN-AMP SECTION OUTPUT, CURRENT
ADJUSTMENT .............................. 26
PRINTED CIRCUIT SHEETS AND
PARTS LIST ............ 27, 28, 29, 30, 31, 32

OTHER PARTS CHART AND LIST ........................ 33, 34

Page 3

SWITCHES AND CONTROLS

Balance Control <
This control adjusts for equal sound from both
left and right channels to compensate for slight
imperfections in program material, variations in
speaker output, and the vagaries of room acous-
tics.

Speakers Switch

This switch is used to choose between one set ol
speakers A and another set B, which may be
installed in the same room or remotely in another
part of your home. It also has a position for
running all speakers at once (:\+B), and another
that cuts them all out for private listening with
headphones (OFF).

Protector Indicator <---4
The protector circuit prevents damage to power
transistors. As soon as the circuit is activated,

the indicator lamp lights up to indicate trouble.

In this case, immediately turn the POWER switch

off and remedy.

Power Indicator -a
The POWER indicator is lit when the IOVVER

switch is turned ON. It remains lit while the

unit is on.

Power Switch -d
The amplifier is on when the POWER switch

lever is moved to the ON position. On the rear

panel of the amplifier there are two A.C. outlets.

The power to the left outlet marked SVVITCHED

is controlled by the POVVFIR switch.

b ("'5 all

Headphones Jack

Plug in a headset for private listening or moni-
toring. The PHONES jack will accept any stand-
ard stereo phono plug but a dynamic headset is
recommended.

Balance Check Switch 4-
This switch is used to check whether the sound
levels from both right and left speakers are equal.
Set the MODE switch to any MONO position;
turn the BALANCE CHECK switch to the TEST
position; and adjust the BALANCE control so
that the sound levels from l)0il1 speakers are

minimized. \Vhen not in use, make sure the
switch is in the NORMAL position.

Low Filter

Turntable rumble and other low-frequency noises
are reduced by setting the LOW FILTER switch
to the ON position.

High Filter

Surface noise from old or worn records, tape hiss
and other high-frequency noises are reduced by
setting the HIGH FILTER switch to the ON
position.

Loudness Control <-
VVhenever the volume is decreased to a low lis-

tening level, the music will seem to lose much of

its bass and some of its treble. This effect is due

to the sensitivity of human hearing. \Vhen the
LOUDNESS switch is on, it provides the correct

amount of bass and treble boost required to com-

pensate for this change.

SELECTOR

Muting Switch

The MUTING switch attenuates music by 20 dB
over the whole frequentiy range. It is used to
eliminate interstation tuning noise, to suppress
the background noise heard when changing a
record, and to reduce the over-all sound level
temporarily while playing a record and other
program sources.

Tape Monitor Switch

This switch enables you to compare a recorded
tape with the original program. Vthn this
switch is in the PLAY BACK position, the rec-
orded tape is heard from the speakers. Monitor
ing is only possible with a 3-head tape recorder.
Note: When you play back through the amplifier,
the TAPE MONITOR switch should be in the
ILAY BACK position as well. When not in use,
make sure the switch is in the SOURCE position.

_4_

Page 8

THREE-CHANNEL STEREO

MAINTENANCE

Three-Channel Stereo

In the three-channel stereo arrangement, one
woofer is connected to the center channel and a
tweeter/midrange speaker system is connected to
the right and left channels. This concept is based
on the fact human ears are not sensitive to the
direction of bass tones of less than 200~300 Hz.
The advantage is that only one woofer is enough
for this stereo arrangement and that lows are repro-
duced more effectively.

The AU-777A is provided with output terminals
for a center-channel amplifier. If you wish to con-
nect a center-channel speaker for the three-channel
stereo arrangement, connect an additional amplifier
to the HIGH CUT terminal (the frequencies of
more than 159 2 are cut off in the filter circuit of

the AU-777A); and then connect the third speaker
to the center-channel amplifier. Another method

is to connect a monophonic power amplifier to the
FLAT terminal and the third speaker to the am-
plifier. In this case, mixed sound from the right
and left channels does not pass through the filter
circuit.

MAIN ANP.

* LEFT CHANNEL
RIGHT CHANNEL

CENTER-CHANNEL

LEFT SPEAKER SPEAKERMOOFER) RIGHT SPEAKER

__.13_

PM Connectors

Warning: Be Sure to pus/1 the POWER switch
OFF before removing the PM connectors.

The PM connectors hook up the PRE OUTPUT
and MAIN INPUT terminals on the rear panel of
the amplifier so that the pre and main amplifiers
can be used individually and separately. When the
PM connectors are removed, the pre and main
amplifier circuits are opened. They should not be
removed except when connecting additional pre.
and/or main amplifiers. Refer to the section titled
Separate Pre-amp and Main-amp Circuits.

Balance Check

Headphones cannot be controlled by the BALANCE
CHECK switch. Before using the headphones, bal-
ance unequal sound levels from the speakers by
using the BALANCE CHECK switch as described
in the section titled SWITCHES AND CON-
TROLS, and then use the headphones.

Phasing of Speakers

Stand about 10 feet in front of and midway between
the speakers and listen to any monophonic repro-
duction. If the speakers are correctly phased, the
sound will seem to come from between the speakers.
If the sound is not directly in front of you, the
speakers are incorrectly phased. To correct this,
switch the amplifier off and reverse the leads to one
speaker.

Care should be taken not to connect a single speak-
er system between the SYSTEM A and B tenni-
nals.

Hum and Howling

If, when using a tape recorder or record player,
unpleasant humming or howling is heard. it is
usually a result of the following.

The record player is placed on or near the speaker
box causing sound waves to be transmitted from
the speaker to the player (howling). To prevent
this, place the record player away from the speaker
box or put a thick cushion between the two com-
ponents.

A low buzzing sound will also be produced if ade-
quately thick shieldwire is not used for connections,
or if connections have not been properly made. Be
sure that the shieldwire is properly soldered to the
pin-plugs as illustrated in Connecting Wire, and
that the motor and pickup arm or the record player
are properly grounded.

Speaker Impedance

Combined impedance of speakers in each channel
should not be less than 4 ohms. Too low impedance
may activate the PROTECTOR circuit or may
cause damage to the amplifier after use over a long
period.

Tape Recorder

1. Tape recorded sound cannot be controlled by
the controls and switches on the front panel of the
amplifier. They control sound from the speakers
only.

2. For better results, record directly through the
AU-T77A, rather than through microphones placed
in front of the speakers.

3. Before connecting and operating the tape record-
er, be sure to look up the manufacturers operating
instructions.

4. The TAPE MONITOR switch should be in the
SOURCE position except when the tapes are being
monitored or played back by the tape recorder.
When the switch is in the PLAY BACK position,
signals from any other source will not be heard from
the speakers.

_|4_

Page 11

TROUBLESHOOTING CHART

If the amplifier is otherwise operating satisfactorily. the
more common causes of trouble may generally be at- 3.

tributed to the following:

1. Incorrect connections or loose terminal contacts.
Check the speakers, record player. tape recorder. antenna 4.

and line cord.
2. Improper operation.

Before operating any audio

tions.

components, be sure to read the manufacturer's instrqu

Improper location of audio components. The proper
positioning of components, such as speakers and turn-
table. is vital to stereo.

Defective audio components

The following are some other common causes of mal-
function and what to do about them.

PROGRAM
SOURCE SYMPTOM PROBABLE CAUSE WHAT TO DO
Tuner Constant or intermit- Discharge or oscillation caused Attach a noise limiter to the elec-

tent noise heard at cer-
tain times or in a certain
area

Noise heard at a partic»

ular time of a day, in a
certain area or over part
of the dial during AM
reception

. High-frequency noise
during AM reception

Noise during FM reccp.
tion

A series of pops
I
l

¥

l * Ignition noise caused by an auto,

by electrical appliances, such as
fluorescent lamp. TV set, DC.
motor. rectifier and oscillator

Natural phenomena, such as at-
mospheric conditions. static, stray
and thunderbolts

Insufficient antenna input due to *
reinforced concrete walls or long
distance from the station ,.,

Wave interference
electrical appliances

from other

This results from the nature of *
AM broadcast

Adjacent-channel interference or I *

beat interference

TV set too close to the audio
system

Poor noise limiter effect or too
low S/N ratio due to insufficient
antenna input ,

Note: FM reception is affected con-

station's power and antenna
efficiency. As a result. you ma
receive one station quite well
while having difficulty in recei~
ving another station. i

siderably by the broadcasting

a:

motorcycle or the like

trical appliance that causes the
noise, or attach it to the power
source of the amplifier.

Install an outdoor antenna and
ground the amplifier to raise the
Signal

Reverse the power
receptacle conneCtions.

cord plug-

If the noise occurs at a certain
frequency. attach a wave trap to
the ANT. input.

Keep the set at a proper distance
from other electrical appliances,

Install the antenna for maximum
antenna eIIiCiency.

In some cases, the noise can be
eliminated by grounding the amp-
lifier or reversing the power cord
plug-receptacle connections,

Although such noise cannot be
eliminated by the amplifier, it is
advisable to set the TREBLE cont-
rol to the minimum counterclockwise

ition possible and switch on the
HIGH FILTER.

Keep the TV set at a proper dis-
tance from the audio system.

Install the antenna for maximum
signal strength.

If this does not prove effective.
use an outdoor antenna designed
exclusively for FM. When you
use a TV antenna for both TV
and FM with the help of a divider.
make sure the TV reception is not
affected.

An excessive long antenna may
cause noise.

Keep the antenna and its leadvin
wire away from heavy traveled
roads or raise the antenna input.

PROGRAM
SOURCE

SYM PTOM

PROBABLE CAUSE

WHAT To Do

(continued)

Noise heard during FM i *
stereo. but not heard
during FM mono recep-

The service area of the FM stereo l
broadcast is only half that of the
FM mono broadcast ,

x

is

Record player placed directly on I

the speaker box I

Use of wire other than shielded
wire

Loose terminal contact

Shielded wire too close to the line
cord, fluorescent lamp or other
electrical appliances

Nearby amateur radio station or
TV transmissmn antenna

Worn or old record
Worn pick -up needle
Needle covered with dust
Improper needle pressure

*

is

»

Install the antenna for maximum
antenna input.

Switch on the HIGH FILTER and/or
set the TREBLE control to the
minimum counterclockwise position
possible.

Put a cushion under the record

player.

Experiment with several different
arrangements before deciding on the
final positions of the speaker and
record player.

Use a shielded cord for connections.
Switch on the LOW FILTER.

The connecting cord should be as
short as possible.

Don't raise the BASS loudness too
much.

Consult the nearest Radio Regula-
tory Bureau.

Set the TREBLE control to the
minimum counterclockwise position
possible and/or switch on the HIGH
FILTER.

Clean or replace the needle.

tion
Record play- Hum or howling *
er, tapc re-
corder or tape a
deck
3
13
*
Surface noise *
I
if
X
Common to The BALANCE control "
all program , is not in the mid sources tion when equal sound

comes from both left
I and right channels.

Due to imperfections in program
material. variations in speaker out
put or asymmetry in room acoustics,
the BALANCE control is not al-
ways set to the mid-position.

it

Set the MODE switches to MONO
and adjust the BALANCE control
so that the sound is heard from a
point midway between the two
speakers.

__2o_.