Pioneer QX-646 User manual

OPERATING INSTRUCTIONS
(Dr:roNEEFl'

Thank you for the confidence shown us in purchasing
a Pioneer 4-channel receiver, model QX-646. This 4-channel
solid state receiver will lead you into the exciting world
of 4-channel sound in all its varieties: discrete 4-channel
tapes or disc records (CD-4), regular matrix (RM) as well as
SQ matrix records and broadcasts. lf you only have two
speaker systems at the moment, the QX-646 will also serve
LINE VOLTAGE AND FUSE
The QX-646 is available in two models; one model
operates only on L20V, and the other operates on
one of the five line voltages; 110V, 1,20V,130V,
220Y and 240V.
If your QX-646 is the latter model, set the unit to
the proper line voltage by following the procedure
described below.
CHANGING LINE VOLTAGE SETTING AND
FUSE
To remove the fuse, turn the fuse cap located on
the line voltage selector in the direction indicated
by the arrow. Then remove the fuse plug from the
unit. Put the fuse plug so that the proper line
voltage marking can be seen through the cut in the
edge of the plug. Whenever the position of the
selector is changed, check the rating of the fuse.
A l-ampere fuse is to be used for either 220Y or
240V operation and a 2-ampere fuse for 110V,
120V or 130V operation. If the rating of the fuse
is correct, replace cap.
FUSE REPLACEMENT
If the fuse blows, remove the fuse cap and replace
the fuse with a new one.
6a
"b-qffiw:
as a 2-channel receiver until you decide to step up into
4-channel sound by adding two more speaker systems.
To develop its full potentials, the QX-646 must be com-
bined with other components (speakers, turntable, tape
deck) of equally high quality. Also, please study the fol-
lowing operating instructions carefully to make full use of
this receiver's many possibilities and features.
CONTENTS
LineVoltageandFuse ....2
QX-646 Features and Performance . . . . . . 3
Composition of
a4-channelStereoSystem ..... 4
Hints for Operating
CD-4DiscRecords ......5
Speaker Systems -
PlacementandConnections . ... 6
Antennas and Ground Connections . . . . . 7
ConnectionofTapeDeck. ...... 8
Connectionof Turntable ... .....9
ConnectionDiagram ....... 9
FrontPanelFacilities.. ...11
PreparationsbeforeOperation ... 13
FMandAMReception.. ..74
RecordPlaying .....15
UsingtheAUXJack. .....15
BeforeCD-4RecordPlaying ... . . 15
UsingaTapeDeck. ...... L7
AboutCD-4Record .... ...... 18
Matrix4-channelDecoder ...... 19
Conditions Frequently Mistaken
forMalfunction . .....20
Specifications... ..2L
2

OX.646 FEATURES
Combines All Current 4-channel System
in One Unit
Exciting 4-channel sound is yours in all four of its current
varieties; discrete 4-channel from open-reel and cartridge
tape, discrete 4-channel disc record (CO-+ Oisc record with
an exclusive phono cartridge), RM (regular matrix) and
SQ matrix records and broadcasts.
Extracts 4-channel Sound from 2-channel Program
Sources
The built-in "regular matrix" circuit can convert regular
2-channel program sources (records, tapes, FM stereo) into
wrap-around 4-channel sound, bringing to life the echo
sound components found in practically any record, and
giving your present stereo LPs a totally new and exciting
sound. (lf you wish, you can play them in conventional
2-channel stereo fashion, too.)
Accepts 2 Pairs of Rear Speakers
The QX-646 can drive one pair of front plus two pairs of
rear speakers, for a total of six speakers. The rear speakers
can be turned on and off with a push-button. This makes it
possible to have two different 4-channel speaker arrange-
ments in the listening room and to select one according to
program souces or personal preferences.
Versatile Auxiliary Circuits and Control
The QX-646 is fully equipped with auxiliary controls
including speaker on/off and rear speaker A/B selector
switches, a tape monitor switch, a headphone jack (for
monitoring the front channels only), and terminals for
2-channel as well as 4-channel tape equipment.
FET-equipped FM Tuner
The FM tuner is equipped with an FET in its front end to
improve selectivity and sensitivity. 'Also, the lF stage
employs one hybrid dnd one monolithic lC, replacing
numerous transistors, ceramic filters, etc., and raising the
tuner's sensitivity and selectivity. The FM MPX decoder
works according to the time switching system and boasts
excellent channel separation. Tuning is made easy by the
linear FM dial and the signal meter.
Built-in AM Ferrite Bar Antenna
Sensitive and highly directional. An outdoor AM antenna is
not required in most cases.
TJIONE€R
Low-distortion Audio Amplifier
Both tone controls and equalizatlon amplifier operate
improved frequency response accuracy and flatness
power amplifier is a quasi-complementary design, a
and-true circuit construction.
Looks as lmpressive as lt Sounds
To this 4-channel receiver the word "compact" can not
be applied - it is a rather large, impressive looking unit
whose outward appearance already hints at its superb
performance and versatility. The dial and meter section
is easier to read. Your operation becomes much easier,
complete with the program and mode indicator lighting up
according to desired operation, and the unit comes installed
in a natural walnut cabinet.
PE RFORMANCE
4-Channel Stereo Performance
With a 4-channel stereo tape deck or cartridge tape
player installed, the QX-646 can provide a discrete 4-
channel playback of programs recorded on tape. ln addi-
tion, the QX-646 can reproduce a discrete 4-channel disc
record with a stereo turntable equipped with an exclusive
CD-4 phono cartridge.
4-channel Reproduction from Matrix 4-channel
Source
The self-contained matrix circuit permits 4-channel re-
production from matrix 4-channel records or FM stereo
broadcasts. The mode switch has positions for regular
matrix and SQ matrix reproduction, allowing reproduction
to take either of these forms.
Matrix Reproduction from 2-channel Stereo Source
A 2-channel signal from a record or FM stereo broadcast
can be reproduced in 4-channel form via the regular or
SQ matrix circuit. ln this case, the result is an improve-
ment over ordinary 2-channel stereo reproduction.
2-channel Stereo Performance
Conventional 2-channel stereo performance can be provided
through an arrangement or two speaker systems in the
front; left-side speaker system and right-side speaker sys-
tem.
for
fhe
ied-
T
tri t
3

COMPOSITION OF A 4-CHANNEL STEREO SYSTEM
A 4-channel stereo system with the QX-646 can include
two or even three pairs of speaker systems, a turntable,
a tape deck (reel-to-reel or cassette), a cartridge tape
player, etc. (see Fig. 2).
INSTALLATION
For safety and reliability and to protect the outward
appearance of each component, please do not install
them in any of the following places:
. In direct sunlight or near heating units.
. In a poorly ventilated, dusty, or damp place.
. In an unstable place where there is significant vibration
or inclination.
Also, when playing CD-4 records, do not install near
poorly shielded electronic equipment or equipment emit-
ting interference signals, (e.9. television set), since high
frequency characteristics up to 45kHz are required for
CD-4 records.
CARTRIDGE TAPE PLAYER FRONT SPEAKER SYSTEMS
TU R NTAB LE ox-646
TAPE DECK
4-channel
or 2-channel )
REAR SPEAKER SYSTEIVIS BFig.2
A WORD ABOUT ROOM ACOUSTICS
The quality of reproduced iound varies according
to the size and shape of the room, the materials
of walls, floor and ceiling and the amount and
arrangement of furniture. Too harsh or "bright"
a sound usually results from too many hard re-
flecting surfaces, and/or too low a ceiling. This
condition is improved by having ample carpet
area or covering the wall (especially that facing
the speakers) with a thick curtain. On the other
hand, too many absorbing surfaces will tend to
"soak up" the sound, resulting in a certain "dead-
ness." Furniture may be rearranged to provide
irregular reflection of the sound.
ABOUT SPEAKER SYSTEMS
For the best 4-channel stereo performance, it is
desirable to use four speaker systems having the
same characteristics. if it is difficult to satisfy this
requirement, it is suggested that speaker systems
be selected and arranged as follows:
o Select two speaker systems having the same
characteristics, and arrange them in the front.
o For the rear channels, select two speaker sys-
tems as similar to the front speakers as possible.

PION€EIT
HINTS FOR OPERATING CD-4 DISC RECORDS
TURNTABLE
The CD-4 disc record is engraved by high frequency
signals based on a 30kHz carrier, which extends up to
45kHz. Compared to conventional 2-channel disc records,
the recording level is low. Therefore, it is desirable to
take note of the following suggestions connecting the
CD-4 disc record reproduction tumtable.
o The PHONO MOTOR must operate almost without
vibrations, revolve at constant rotational speed with-
out wow and flutter, and produce an excellent signal-
to-noise ratio.
. The TONEARM must have sufficient trackability, that
is, can track the groove with light tracking force. Also
it must have an anti-skating device and lateral balance
to adjust the tonearm so that the tracking force can
be distributed equally to both the left and right walls
of the record groove.
PHONO CARTRIDGE
To effectively reproduce the wide frequency range of
CD-4 records over a long period, it is essential for CD-4
disc record reproduction to use an exclusive cartridge.
Make certain that the stylus is in position when the
phono cartridge is installed, and that the stylus goes
down vertically onto the record surface when the phono
cartridge is replaced, so that separation and sound quality
remain the same as before.
RECORD HANDLING
Since the groove of the CD-4 disc record is delicately
engraved, even a small amount of dust can cause un-
pleasant noise and poor sound quality. In addition, it
can scratch the record surface, reducing its service life.
Since the warped disc record is never reproduced exactly,
it is desirable to exercise utmost care in handling them.
Before and after playing the disc, it should be cleaned
with high quality cleaner, not a spray-type. It must not
be washed with water.
STYLUS CLEANING
If dust clings to the stylus, sound quality and separation
become poor, 4-channel stereo is impossible to reproduce,
and the disc is damaged.
The stylus must always be cleaned whenever a record
playing is over. If dust is difficult to remove, clean care-
fully with commercial available alcohol stylus cleaner.

SPEAKER SYSTEMS-PLACEMENT AND CONNECTIONS
SPEAKER SYSTEM ARRANGEMENTS
As shown in Fig. 3, the 4-channel system employs four
speakers, one each on the left and right at the front and
rear. Locating the rear speakers anywhere in the blue-
shaded area of this figure will give an ample 4-channel
effect. As model QX-646 permits a total of six speaker
systems to be connected, two speaker systems are placed
at front left and right, and others (two pairs of speaker
systems) can be placed within the blue-shaded area of
Fig.3. Some 4-channel records and tapes call for speci-
fied speaker ailangements. Please observe the manufac-
turer's instructions.'
CONNECTION
Use common two-pole lead wires, preferably with differ-
ent colors for the two leads for easy identification'
Speaker wire is often supplied with the speakers.
Connect the speaker placed at the front left to speaker
output terminals CH 1 (FRONT SPEAKERS marked
"L") on the QX-646. Likewise, connect the speaker
placed at the front right to speaker output terminals CH
3 (FRONT SPEAKERS marked "R").
Connect the speaker placed at the rear Ieft to speaker
output terminals A CH 2 (REAR SPEAKERS marked
"L") on the,QX-646. Likewise, connect speaker placed at
the rear right to speaker output terminals A CH 4 (REAR
SPEAKERS marked "R").
To connect the other speaker systems to the speaker
output terminals B, do the same as above.
Be sure to connect the plus ( + ) terminal (red terminal)
on the QX-646 to the ( + ) terminal on the speaker, and
the minus ( - ) terminal (black terminal) on the QX-646
to the ( - ) terminal on the speaker.
For connection, remove about 1Omm (1/3") of insulation
from the lead wires. If the wire core is stranded, twist it
to prevent hair wires from sticking out. On the ( + ) side,
push the red clamp-lever on the terminal up and insert
the wire end into the hole, then release the lever - the
wire will be clamped securely in the terminal. On the ( - )
side, push the black clamp-lever on the terminal down,
insert the wire and release the lever.
RIGHT CHANNEL
SPEAKER SYSTEM PLACEMENT
SPEAKER OUTPUT TE RMINALS
RIGHT CHANNEL LEFT CHANNEL
SPEAKER SYSTEMS
SPEAKE R
LEAD WIRES
Fig.3
Fig. 4
SPEAKER LEAD WIRES
Strip the wires of
their ends.
Then twist them.
"w=
Fig. 5

PIONEEIrt
ANTENNAS AND GROUND CONNECTIONS
FM ANTENNA
FM broadcast are considerable weakened by intervening
mountains, buildings, etc. or if the antenna is inside a
concrete building. This should be considered when
deciding upon the type and location of the FM antenna.
Connection and Location
For areas with a strong signal, especially in wooden
houses, use the T-type indoor antenna (supplied).
. As shown in Fig. 6, first connect the antenna leads to
the proper terminals on the rear of the QX-646. Then
spread out the cross section and attach it to a wall, etc.
after deciding upon the best location by listening to an
FM broadcast and watching the SIGNAL meter deflect
(see the explanation on p. 14).
When a special FM outdoor antenna is required...
. If there is a great deal of noise during FM reception
using this antenna, replace it with a special FM
outdoor antenna (or a combination FM/TV antenna).
connect it to the proper terminal(s), as shown in
Fig.7.
NOTES:
l. FM antennas are available in any type. Select the best type after
securing the advice of your audio dealer.
2. In heavy traffic areas, industrial zones or near high'voltage electrical
equipment, a great deal ol interference tnty enter despite careful
antenna selection. In such a case, talk things over with your audio
dealer. It mty be advisable to use a 75C. coaxial cable between the
antenna and the QX-646. Connect to the cable terminal as shown in
Fig. 7.
AIII ANTENNA
First tune in an AM station (see the explanation on p. 14).
Then, while watching the SIGNAL meter deflect, adjust
the AM ferrite antenna on the rear panel for the best
signal (see Fig. 9).
1. If the ferrite antenna does not provide satisfactory AM
reception, connect the vinyl-sheathed AM lead antenna
to the proper terminal. Stretch it out with the other
end as high as possible (see Fig. 6).
2. If reception is still poor, construct an outdoor antenna
between two poles, etc., as shown in Fig. 7. Use
vinyl-sheathed lead, and connect to the QX-646 AM
antenna terminal.
GROUND
F'or optimum safety and noise-free performance, it is
desirable to connect the GND terminal to a good ground
(see Fig. 7).
Strip the coaxial cable as shown in (A).
Loosen the screws and connect the cable as shown in (Bl.
Then tighten all screws for a connection like (C). Fig. 8
DIRECTION OF
BROADCAST
ANTENNA FM oUTDOOR
ANTENNA
Fig.6
AM OUTDOOR ANTENNA
Fig.7
GROUND
INNER
CONDUCTOR @
OUTER
SHIELD
(BRAID)E
CABLE
(75-ohm)
FM INDOOR ANTENNA
AM LEAD ANTENNA
AM FERRITE ANTENNA Fig. 9

CONNECTION OF TAPE DECK
The QX-646 can be connected to either a 4-channel or a
2-channel tape deck (reel-to-reel, cassette) for recording
and playback. Use connection cords usually supplied with
the tape deck. For connections, use the following
procedures:
RECORDING
Connect the LINE INPUT jacks of tape deck to the
TAPE REC jacks of the QX-646. Be sure that all
connections are correct as follows:
PLAYBACK
Connect the LINE OUTPUT (or TAPE MONITOR) jacks
of tape deck to the TAPE MON jacks of the QX-646. Do
the same confirmation as follows:
Tape MON Jacks
(ox-646)
Line Output Jacks
4-Channel
Tape Deck 2-Channel
Tape Deck
Front Left (CH.1) Front Left (CH.1) Left (cH.L)
Front Right (CH.3) Front Right (CH.3) Risht (cH.R)
Rear Left (CH.2) Rear Left (CH.2)
Rear Right (CH.4) Rear Right (CH.4)
Connection via REC/PB Connector
Instead of the recording and playback connections just
described, the 2-channel stereo tape deck can be con-
nected to the REC/PB connector (DIN-type) of the
QX-646 if an identical connector is provided in the tape
deck, too. The required DlN-cable is available at all hi-fi
and radio stores. This single cable completes all playback
and recording connections at the same time. Use a
DlN-cable for tape deck-to-amplifier connection. Note
that the REC/PB connector corresponds to the TAPE
REC and TAPE MON terminals - the signal must be
controlled with the TAPE MONITOR switch of the
QX-646.
4-CHANNEL
TAPE DECK Fis. 10
FOR TAPE PLAYBACK
4-CHANNEL
TAPE DECK Fig. 11
NOTE:
Also, in the case of a three-head tape deck, connection
via a DlN-cable may sometimes cause crosstalk. With
three-head tape decks, connection to the REC outputs
and MON inputs via regular phono cables is preferable-
ll
::ili iif .s".
Tape REC jacks
(ox-646)
Line lnput Jacks
4-Channel
Tape Deck 2-Channel
Tape Deck
Front Left (CH.1) Front Left (CH.1 Left (cH.L)
Front Right (CH.3) Front Right (CH.3 Risht (CH.R)
Rear Left (CH.2) Rear Left (CH.2
Rear Right (CH.4) Rear Right (CH.4
rl
l t-----,
L----r i
2-CHAN N E L
TAPE DECK
-r. !i
Eii
2-CHANNEL
TAPE DECK
a

PREPARATIONS BEFORE OPERATION
BEFORE SWITCHING THE POWER ON
Initially, set the controls as follows:
1. VOLUME control at MIN.
2. All three BALANCE controls at center.
3. All BASS and TREBLE controls at center.
4. FM MUTING switch pushed at OFF.
5. TAPE MONITOR switch not pushed (off posi
tion).
6. FUNCTION switch at FM MONO.
?. MODE switch at 4CH CD-4.
8. SPKR ON - OFF switch ON (released).
9. SPEAKERS REAR A - B switch at A or B,
depending on connection of rear speaker sys-
tems.
Finally, turn POWER switch ON. Unit is now ready
to operate.
CONFIRMATION OF CONNECTIONS AND
SOUND VOLUME ADruSTMENT
These confirmation and adjustment are as follows:
If you have a stereo turntable equipped with an
exclusive CD-4 phono cartridge, please refer to
"Before CD-4 Record Playing" on page 15.
Channel Confirmation
With all controls set as above, proceed as follows:
1. Set the FUNCTION switch to FM MONO and
tune in an FM broadcast.
2. Turn up volume to average listening level. Con-
firm that sound comes from the four speaker
systems (front and rear, left and right).
If there is no sound coming from one or more
of the speaker systems, check speaker system
connections.
3. Turn the FRONT-REAR BALANCE control to
the extreme left. At this time, sound should
come from the front speaker systems only.
4. Turn the FRONT BALANCE control to the
extreme left and confirm that sound comes from
the front left speaker system (CH. 1) only. Then
turn this control to the extreme right and con-
firm that sound comes from the front right
speaker system (CH. 3) only.
5. Turn the FRONT-REAR BALANCE control to
the right and confirm that sound comes from
the rear speaker systems alone.
6. Turn the REAR BALANCE control to the ex-
treme left and confirn that sound comes from
the rear left speaker system (CH. 2) only. Then
turn this control to the extreme right and con-
firm that sound comes from the rear right speak-
er systems (CH. 4) only.
If checks do not conform, speaker system connec-
tions may be in error. Recheck them. After con-
firming that operation is normal, set these controls
to mid-positions.
Adjustment of Level Balance Among 4-channels
1. After the above confirmation, turn the volume
up to normal listening level.
2. Turn the FRONT-REAR BALANCE all the
way to the left. Then, tum the FRONT BAL-
ANCE control in either way to balance the
level between the left and right speaker systems.
3. Now turn the FRONT-REAR BALANCE all
way to the right. Then, turn the REAR BAL-
ANCE control in either way to balance the level
between the left and right speaker systems.
4. Finally, turn the FRONT-REAR BALANCE
control either way to balance the level between
the speaker systems in the front and rear.
rrtoNeEfl
e,.J::."**>
. REAR RIGHT
'"^z>
REAR
REAR LEFT
FFTTI\IT FFETNT FIEAFI
"--i\ ,/ \--I--< \
t/zAN / '/l^'\ \
.(( )l / 1( )I'
\1 'V
LEFT HIGIHT FIIG'HT
Fig.12
toaota= I
SPEAKER SYSTEM PLACEMENT
Fig. 13

i t r! r
FM AND AM RECEPTION
FM RECEPTION
1. Set the FUNCTION switch to FM AUTO.
2. Set the FM MUTING switch to on (not pushed
position). Do not push the FM MUTING switch
usually unless FM reception is very weak or noisy.
3. Turn the TUNING knob to tune in the desired station
while watching the pointer deflect in the SIGNAL
meter. Best reception is obtained when the pointer
deflects to the extreme right. When the tuned-in FM
station is broadcasting an FM stereo program, the FM
stereo indicator lights uP.
4. Setting the MODE switch to 4CH RM or SQ during
reception of corresponding FM stereo broadcasts by
RM or SQ matrix records permit matrk 4-channel
reproduction. These two modes may also be used
during reception of ordinary stereo broadcasts. The
result will be an improvement over ordinary 2-channel
stereo being obtained from FM monophonic broad-
casts.
5. After the FM station has been tuned in, turn the
VOLUME control to increase the volume in the way
you want, and adjust the BASS and TREBLE controls
to obtain most pleasing tone.
NOTES:
t. If your area is far away from the FM station or reception is noisy,
setting the FUNCTION switch to FM MONO, an FM stereo programis
received as an FM MONO Program.
2. In some countries, model QX-646 is delivered with a selector switch
for adjusting the FM de-emphasis from 50 to 75 psec. If your unit is
equipped with such a switch at the chassis, and if the high sound range
gives an impression of weakness, move the de-emphasis switch to its
other position.
AM RECEPTION
1. Set the FUNCTION switch to AM.
2. Set the MODE switch to 2CH.
3. Turn the TUNING knob to tune in the desired station
while watching the pointer deflect in the SIGNAL
meter.
Best reception is obtained when the pointer deflects
to the extreme right.
4. After the AM station has been tuned in, turn ttte
VOLUME control to increase the volume in the way
you want, and adjust the BASS and TREBLE controls
to obtain the rnost pleasing tone. Note that a matrix
4-channel effect cannot be obtained from AM broad-
casts.
NOTE:
If excessive noise occurs during AM or FM reception and cannot be cured
by the above methods, re-read the section "Antennas and Ground Connec-
tion" (see page 7) for optimum reception.
\2
MODE
r5- ----_l
FIM 4CH
=.-,1
F ig. 14

rJION€EfI
RECORD PLAYING
1. Set the FUNCTION switch to PHONO.
2. Set the MODE switch to match the type of disc record
to be played.
* Note that it is necessary to adiust the Carrier level and Separation for
each four-channel before playing a CD-4 disc record.
For details, see below and the next page.
** Any ordinary 2-channel stereo record other than CD-4 disc records
can be played at either position of RM or SQ as 4-channel perfor-
mance.
3. Set the VOLUME, BASS and TREBLE controls to
desired positions.
USING TH E AUX JACK
1. Set the FUNCTION switch to AUX.
2. Set the MODE switch according to the type of the
program sources connect to the AUX jacks.
3. Set the VOLUME, BASS and TREBLE controls to
desired positions.
BEFORE CD.4 RECORD PLAYING
Before playing aCD-4 disc record, adjust such as "Carrier
Level," "Separation," "Channel Confirmation and Sound
Volume Adjustment" with the supplied test record.
Re-adjustment is required when the phono cartridge and
stylus are replaced, or after a long period of play. For
details, follow the steps described below:
CARRIER LEVEL ADruSTMENT
1. Turn up volume to average listening level.
2. Play the Band 4 to adjust a 30kHz carrier level from
the test record. "SIGNAL FOR 30kHz CARRIER
LEVEL ADJUSTMENT."
3. Listening to the signal (400H2), turn the CARRIER
LEVEL CONTROL knob of the QX-646 on the rear
panel from the right (maximum position) to the left.
4. Turning the CARRIER LEVEL CONTROL knob to
the left, find the changing point of tone quality, at
which the signal becomes distorted. Then turn to the
right to let the knob adjust at a tuming angle of be-
tween 15"-30".
Once the final carrier adjustment is made, the knob must
not be turned except for readjustment after replacement
of phono cartridge or stylus, and after a long period of
play.
CD-4
INDICATOR
LAMP
I\4ODE INDICATOR LAMPS
2 CHANNEL
4 cHANNEL
@ cD-4
FlM
so Fig. 15
NOTE:
If you use a 2-channel phono cartridge of a capacity
larger than specified, you may occasionally feel repro-
duced sound distorted. In this case, turn the SEPARA-
TION CONTROL knob to left (b-) of the QX-646 on
the front panel, to eliminate the distorted sound.
ASC (Automatic Selectivity Control) Circuit
When the engraved grooves of a CD-4 disc
record a.re worn down into a noise un-
pleasant to listen, the ASC circuit is used
for'suppressing such a noise by compensat-
ing for frequency in accordance with a
change of carrier levels.
Type of Record. MODE Switch Position
RM 4-channel record 4CH RM
SO matrix 4-channel record 4CH SO
CD-4 record* 4CH CD-4
Ordinary stereo record * "2CH
3
TEST RECORD (POX.I011I
Fig. 16

CD.4 SEPARATION ADJUSTMENTS
Left (CH. 1- CH. 2) Adjustment
1. Turn up volume to normal listening level.
2. Turn the FRONT - REAR BALANCE control all the
way to the right.
3. Tum the REAR BALANCE control all the way to
LEFT.
4. Play the Band 1 to adjust the separation of left
channels (CH. 1 and CH. 2) from the test record.
..SIGNAL FOR SEPARATION ADJUSTMENT OF
LEFT CHANNELS.''
5. Adjust the SEPARATION LEFT control so that the
.sound volume from the REAR LEFT (CH. 2) becomes
minimum, listening to the test record.
Right (CH. 3 - CH.4) Adjustment
1. Turn up volume to normal listening level.
2. Turn the FRONT-REAR BALANCE control all the
way to the right.
3.Turn the BALANCE REAR control aII the way to
RIGHT.
.Play the Band 2 to adjust the separation of right
channels (CH. 3 and CH. 4) from the test record.
..SIGNAL FOR SEPARATION ADJUSTMENT OF
RIGHT CHANNELS.''
5.Adjust the SEPARATION RIGHT control so that the
sound volume from the REAR RIGHT (CH.4) be-
comes minimum, Iistening to the test record.
If these checks reveal'that.the separation adjustments do
not function as predicted, check all speaker connections.
There must be a wrong connection somewhere.
After confirming that operation is normal, set these con-
trols to mid-positions.
CHANNEL CONFIRMATION AND SOUND VOLUME
ADruSTMENT
1. Tum up volume to normal listening level.
2.Play the Band 3 to check the channel connection and
balance from the test record. "ANNOUNCEMENT
FOR CHANNELS AND SIGNAL FOR BALANCE
ADJUSTMENT."
3. Listening to the test record, confirm
from each speaker system (CH. 1 -
factory.
4. Finally, adjust the sounds from each
(CH. 1 - CH. 4) properly.
that the sounds
CH. 4) are satis-
speaker system
SPEAKER SYSTEM PLACEMENT
Fis.17
LEFT FIIG;HT LEFT FIIGIHT
ao.o,^,a= |
Fig. 18
NOTE:
The knobs must not be turned after final CARRIER
LEVEL and CD-4 SEPARATION adjustment except after
the replacement of phono carfiidge or stylus.
FFrlNT FIEAFI
z \--L< r
/ "/, N \
r 1( )I'
-v/

PIONEETI
I
USING A TAPE DECK
TAPE PLAYBACK
1. Set the TAPE MONITOR switch to ON.
2. Set the MODE switch according to the type of tape to
be reproduced.
Type of Tape MODE Switch Position
4-channel discrete tape 4CH CD-4
2-channel stereo tape 4CH SO
4CH RM
2CH
2-channel recorded tape can be reproduced at either position of RM or
SO to get 4-channel performance.
3. Set the VOLUME, BASS and TREBLE controls to the
desired positions.
TAPE RECORDING
The signal being played over the receiver is always
present at the TAPE REC outputs for recording on tape.
Select the program source with the FUNCTION switch as
usual. Please note that the VOLUME, BASS, TREBLE
controls have no effect upon the signal at the TAPE
REC outputs.
The signal is recorded as it comes from the program
source. Recording levels must be adjusted with the
controls on the tape deck (see Fig. 19).
Monitoring of a Recording in Progress
If the tape deck is a three-head type or equipped with
monitor circuits, a recording in progtess can be monitor-
ed by setting the TAPE MONITOR switch on the QX-646
at position ON (see Fig. 19).
TAPE DUPLICATING
Only with two 2-channel tape decks, not including
4-channel tape decks, you can duplicate tape-to-tape or
edit recordings while re-recording. For stereo program,
with announcements and commercials, and later re-record
on another tape while cutting out unwanted portions.
For duplicating, proceed as follows:
1. Connect two tape decks as shown in Fig. 20.
2. Set the FUNCTION switch to AUX, and reproduce a
recorded program by operating the tape deck plugged
into the AUX inputs.
3. Record the program in the way you want by operating
the tape deck plugged into TAPE REC (MON) jacks.
Operation of the TAPE MONITOR switch allows you
to monitor a recording in progress.
TAPE DECK
PROGRAM /4-CHANNEL \
SOURCES \ oT 2.CHANNEL /
Fis. 19
NOTE:
llhile playing RM (regular matrix) or SQ matrix disc rec-
ord, signal present at CH.2 iack of the REC output iacks
is the same with that of CH.I, and sigrwl present at CH.4
iack, the same with that of CH.3. Accordingly, no 4-
channel tape deck can record such signals in either RM or
SQ effect because the signals do not pass through a
demodulator. If, however, the tape monitor switch is on,
speaker systems will reproduce demodulated 4channel
stereo sounds in either of RM and SQ effect.
TAPE DECK 1 TAPE DECK 2
(for playbackl (for recording)
TUNER
SECTION
ox-646
i^=filt'"'Y(J---*--1 0
. ".'"Y' '"'' TAPE MONITOR
Slrrltch s^ritch
ox-646 Fig.20

ABOUT CD.4 RECORD
In conventional 2-channel stereo records, both left
and right sound information is engraved on the left
and right walls of the 45"/45" record groove. If
this method applies to recording 4-channel sounds,
they must be converted into 2-channel signals once
before engraving them on the walls. This is
generally called a Matrix 4-channel record.
The CD-4 disc record employs a special recording
and reproducing method initially developed in
Japan, in which 4-channel signals can be recorded
independently without converting them into 2-
channel signals.
The CD-4 disc record, two different kinds of
signals are engraved directly on each left and right
wall (Fig. 21). One signal is the conventional signal
with an audible frequency less than 15kHz, and
engraved in the same way as conventional records.
Another signal is an inaudible signal of a frequency
higher than 20kHz. If such signals are reproduced
directly, they are inaudible.
In the CD-4 disc recotd, the other audible signals
are converted into frequency deviation between
20kHz and 45kHz (frequency modulation with
30kHz carrier), and engraved on the walls in
addition to the signal just described.
The A-sound in the figure is reproduced as the
audible sound when the stylus tracks the groove.
TURNTABLE With
CD-4 phono cartridge
However, it is necessary for the B-sound to use the
demodulator. The X-signal which contains the
B-sound is demodulated and the B-sound is extract-
ed from the X-signal, thereby enabling the B-sound
to be audible.
In the actual CD-4 disc record, the A and C sound,
which are audible, contain the sum signals of the
left front plus rear, and the right front plus rear
respectively. Therefore, in a 2-channel system, the
left and right speaker systems can reproduce each
sum signal because of its compatibility.
The B and D sounds, on the other hand, contain
the different signals - the left front minus rear and
the right front minus rear respectively.
For a complete 4-channel system, the four in-
dependent signals, front left, front right, rear left
and rear right can be fed to the amplifier through
the demodulator and the matrix circuitry as shown
inFig.22.
A-sound, audible (1 5Hz-15kHz)
lnaudible X-signal which contains B-sound
(20kHz-45kHz)
Fig.21
STYLUS
C-sound and Y-signal
'7 which contains
/ D-sound
REPRODUCED
SOUND FIELD Fig.22
A-sound and X-signal
ORIGINAL SOUND FIELD
CD-4 ENCODER CIRCUIT
DEMODULATOR MATRTX ClRCUlr
A
B
c
D
LF FF
LEFr 8Rr
LR Fn
r^w
A*B:(Lr*Ln)+(Lr-Ln)=2Lr
A - B - ( L r +L n ) (L r -L n ):2L n
C+D:(R r +Rn )+ (Rr R n ):2R r
C-D:(Rr+'Rn) {Rr Re):2Rn

PIONEETI
MATRIX 4.CHANNEL DECODER
There are two types of matrix 4-channel systems,
the RM (regular matrix) and the SQ matrix. Source
information comes directly from matrix 4-channel
records now available on the market or indirectly
from FM broadcasts of such records. As these
methods are not compatible, two decoders must be
added to obtain 4-channel reproduction which
exhibits the inherent features of each.
Regular Matrix
As shown in the Fig.23, signals L, and R, from
a matrix 4-channel record (or FM broadcast) pass
through phase shifters and appear as four separate
outputs. This figure also shows that the o portion
of signal R, is added to signal L-' to form front
Ieft signal Lu and that the o portion of signal L, is
added to signal R, to form front right signal Ru.
The 0 portion of signal R.,. with phase led 90'
(+jRr ) is added to signal L-, with phase lagged 90'
( -jlr ) to form rear left sigrrals L* , while the B
portion of the -jL, signal is added to the +jRr
signal to form rear right signal R*.
LF (front left, CH. 1): Lr + eRr
RF (frontright, CH. 3): Rr + ql-r
LR (rear left, CH.2\: -jl,r + jBRr
RR (rear right, CH. 4): +jRr -jBLr
Using this approach, unnatural images are elimi-
nated and at the same time realism is effected.
Even if 2-channel stereo records (FM broadcasts)
supply the source material, the resultant effect is
an improvement over ordinary 2-channel stereo
sound.
MATRIX
4.CHANNE L RECORD
(OR FM BROADCAST) REGULAR MATRIX DECODER
LF /CH. I
(Lr+aRr)
LA/CH.2
( jL r +jBRr )
RF,/ CH.3
(Rr+aLr)
Ra/CH.4
(+iRr jBLr)
Fig.23
SQ Matrix
As shown in the Fig.24, signals L, and R-' from
an SQ matrix record (or FM broadcast) pass
through phase shifters and appear as four separate
outputs. This figure shows that signal L, becomes
signal Lu (CH. 1) and that signal Rt becomes
signal R, (CH. 3), without any alteration.
A phase shifter lags the phase of signal L., by 90,'
after which the lagged signal is added to signal R..
Level of the resultant signal is dropped bV 1l{2
+ 0.7 and phase is inverted to form CH.2 signal
L*. In the same manner, signal L' is add'ed to
signal Rr with phase lagged 90". The level is
reduced by Ll.r/-Tlo form signal Ro.
LF (CH.l): Lr
RF (CH.3): Rr
LR (CH.2): +j0.7L, - 0.7Rr
RR (CH.4): -j0.7Rr +0.7Lr
Thus, it is seen that separation in the SQ matrix
system is better than that in the regular matrix
system, that is, separation between L. and R.. In
matrk reproduction of 2-channel records (FM
broadcasts), front (Lr. , Re ) separation theoretic-
ally becomes infinite. At the same time, rear signals
are 90' out of phase to front (LF, RF ), resulting in
a feeling of depth which corresponds to a large
hall.
LF ,/ CA. t
(Lr)
LR,/CN.2
( +io.7L; o.?Rr)
RF /CH.3
(Rr)
RRICH 4
( -jo.7Rr+o.7Lr)
Fig.24
NOTE:
L7 and R, are sigtwls from a record or FM broodcast. Term -i
denotes that the phase of the signal has been lagged 9f (with
a phase shifter), while term +j denotes that the phase of the sigrwl
has been led 90".
SO MATRIX DECODER
PHASE REVERSE
(180.)
FM STEREO
TUNER
PHASE SHIFTER
I
iLl-'s"
l(+J)

CONDITIONS FREOUENTLY MISTAKEN FOR MALFUNCTION
Noise: There are a variety of noises relating to the
operation of a hifi unit. These are generally
divided into two types; (1) the unit is faulty (a
transistor or part has deteriorated) and (2) an
external source is adding to the unit.
When a hifi unit produces an unpleasant noise, it is
often assumed that the unit is faulty, but statistical
records indicate that the majority of noises pro-
WATCH FOR THE FOLLOWING CONDITIONS; THESE ARE ALSO APT TO BE MISTAKEN FOR MALFUNCTIONS.
duced in high-fi acoustic units result from external
sources of noise: Due to the inherent high sensi
tivity and the high fidelity in reproduction, the
unit amplifies and reproduces extraneous noises,
however small, into definite output noise. If your
receiver produces a noise, check according to the
following table and trace out the source of noise
for the appropriate corrective action.
SYMPTIOM SUSPECTED SOURCE OF NOISE DIAGNOSIS AND REMEDY
TA
F
o
o
G
(D
o
F
=
z
l.IJ
F
:
z
ul
I
=
Continuous or intermittent
noise like ijjjij or zzzzzz. .Static (lightning)
. Fluorescent lamp, motor, or thermostat
may be in use in house or in the vicinity of
the house.
ln many cases, it is very diff icult to remove the source
of noise. ln order to make the radio input larger than
the noise level, set up a good outdoor antenna and
make a complete grounding.
When a station is tuned in,
hum is mixed in the pro-
gram.
. Poor fluorescent lamp, motor, or electric
heater may be in use in house or near the
house.
Reversing the line plug may occasionally alleviate this
noise problem. Usually it is very diff icult to eliminate
the noise.
Hissing sound noise in AM
(medium wave) reception. . The frequency of an adjacent station is
interfering with that of the station being
tuned in {10kHz beat interference).
. TV set is on in the same house with the
rece iver-
lmpossible to remove such interference. lf the case of
such noise is in the TV set, increase the distance be-
tween the TV set and receiver.
Static noise (in particular,
when automobiles run
close to the house).
'White noise generated from automobile
engi nes.
. High frequency sewing machine or weld-
ing machine being used near your house.
ln an area surrounded by hills or high buildings, the
FM input signals are very weak, Thus the noise limiter
in the circuit loses its function. Set up an FM outdoor
antenna having many director elements.
Reception of FM stereo
program contains more
noise than FM mono pro-
gram.
. Note that the service area covered by an
FM stereo broadcast is about 50% of that
of a regular mono broadcast.
lncreasing FM input signal may alleviate this problem.
Use an exclusive FM outdoor antenna instead of the
indoor T-type antenna.
@
o
tr
o
O
UJ
tr
(,
=
J
o-
z
TIJ
I
=
Hum or buzz. When
switched to radio recep-
tion, the noise disappears.
Poor connection of shielded wire. (a)
Jack connection is loose. (b)
Line cord of fluorescent lamp is near the
shielded wire. (c)
Poor grounding. (d)
Ham transmitting station or TV transmit-
ting station is near your house. (el
Correct the conditions stated in (a), (b), (c) or (d). ln
case of (e), report it to an official activity.
Output tone quality is
poor and mixed with noise.
Treble is not clear.
stylus wears out. (a)
Record wears out. (b)
Dust adheres to stylus. (c)
Stylus is improperly mounted. (d)
stylus pressure is not.proper. (e)
The TREBLE level is too high.
Check (a) through (e) and correct the condition.
Lower the TREBLE level.
SYMPTOM SUSPECTED SOURCE OF NOISE DIAGNOSIS AND REMEDY
Power is not turned on
although the power switch
is set to ON.
Fuse blows. (a)
Line plug is loose, (b) Check (a) and (b) and correct the condition.
Power ON but speakers
produce no sound. Blown-out PROTECTION fuse. Replace with the supplied PROTECTION fuse.
ln playing a record, in-
creasing the volume causes
howling.
. Distance between the turntable and the
speakers is too short.
'The place on which the turntable or
speakers are set is unstable.
Change the distance or rearrange the installation
increase of the unit and speakers. (lnstalling the
turntable on a firm, solid stand may alleviate this
problem.)
Do not enhance the BASS sound level excessively.
20

SPECIFICATIONS
Semiconductors
FETs.. .........9
lcs... .........5
Transistors ......109
Diodes. ....45
Amplifier Section
Continuous Power Output
20Hz - 20k{z (2 channels driven)
I0w + 10w / 10w + 10w (8a)
l kHz (4 channels driven) 10W x 4 (8sl), 1 1W x 4 (4o)
lkHz (2 channels driven) 13W + .l 3W / 13W + 13W (8o)
15W + 15W / 1SW + 15W (4'C})
lkHz (Each channet driven) 15w / 15W I 15w | 15w (8o)
2ow | 20w | 20w | 20w (4o)
Music Power Output (lHF) 80W (8o), 108W (4O)
Harmonic Distortion
(Continuous Power Output) Less than .l %
I ntermodulation Distortion
(Continuous Power Output) Less than 1 %
Power Bandwidth
(lHF,4 channels driven 8Sl)
(lHF,2 channels driven 8fl)
Output, Speaker
Head phone
Damping Factor (1kHz, 8s})
lnput Sensitivity / lmpedance
PHONo (2cH.)
AUX
TAPE MONITOR
TAPE MON ITOR
(DlN Connector)
Output Level
TAPE REC
TAPE REC (DlN Connector)
Frequency Response
15Hz-20kHz (H.D.1%)
.l0Hz-30kHz (H.D. i%l
; lll;J;j,'i::f I ro-, u" I
Front (CH.i, CH.3)
40
2.5 mV/100ko
180mV/90k.r}
180mV/90ko
180mV/90ksl
.l 80mV
30mV
PHONO (RIAA equalization) 30Hz -15kHz t0.5dB
AUX,TAPE MON 1OHz -100kHzr3dB
Tone Control
BASS
TREBLE
Loudness Contour
(Volume control set at
Hum & Noise (lHF, Short-circuited, A Network)
PHONO More than 70dB
AUX, TAPE IVION More than 90dB
CD-4 Demodulator Section
lnput Sensitivity 2.5mV (1 -5mV Adjustabte)
lnput lmpedance 100k0
Distortion 0.01%
S/N (lHF, A Network) More than 70dB
Separation (STD Tesr Signal at 1 kHz)
Left - Right 50dB
Front - Rear 30dB
Frequency Response 20Hz - 15k9z
+13dB, 12.5d8 (100H2)
+1 1 .5d B, -8.5d8 (1OkHz)
-40d B position )
+10d8 (100H2), +Sae (t otuz)
PIONEER
FM Tuner Section
Usable Sensitivity (lH F)
Capture Ratio (lH F)
Selectivity (lHF)
Signal-to-Noise Ratio
lmage Rejection
lF Rejection
Spurious Rejection
AM Srrppression
Harmonic Distortion
Stereo Separation
Sub Carrier Suppression
Antenna lnput
Muting
AM Tuner Section
Usable Sensitivity
Mono
Ste reo
1 kHz
2.2pV
3dB
40d B
65d B
More than 50dB
More than 85d B
More than 80dB
50d B
Less than 0.6%
Less than 0.8%
More than 40dB
35d B
300O Balanced
75,f} Unbalanced
ON-OFF
(lHF, Ferrite antenna)
(rHF)
Selectivity (lHF)
Signal-to-Noise Ratio
lmage Rejection
lF Rejection
Antenna
Miscellaneous
Built-in CD-4 Demod ulator
Regular Matrix Decoder
SQ t\4atrix Decoder
Power Requirements AC .l 20V 60Hz or 1 10V, .l 20V,
139y,220Y and 240V (Switchabte)
50/60H2
Power Consumption (Max.) 160W
AC Outlets
Dim ensions
Weight Without Package
With Package
Furnished Parts
FMT-typeAntenna .......i
co-4restRecord(PeX-irjrlj .. : : : : : : :. :. . . .. .. .1
Operatinglnstructions .......1
Fuses1.5A(Protection) .....2
Fuse 1A(for5-linevoltagemodelonly) . ... .. .1
Fuses 2,A (for 5-line voltage model only) . . . . . . .2
NOTE:
Specijications and the design subiect to possible modification
without notice due to implovements.
300pV/m
1 5pV
25dB
50d B
More than 45dB
More than 30dB
Built-in Ferrite Loopstick Antenna
Switched 1, Unswitched 1
s2s(W) x 149(H) x 360(D) mm
20-1 1 116(w) x s-718(H) x
1a-3l16(D) in.
12.3ks (27tb 2oz)
1 4.7 kg (32tb 1 oz)
21

FIG'NEEFI ELECTFIGINIC CclFIPclFIATIclN
15-5, 4-Chorne, Ohmoni-nishi, Ohta-ku, Tokyo, Japan
U.A. P|CINEEFI ELE CTFIG'NICA CG'FIFGIFIATIG'N
178 Commerce Flo€id, Canlstadt New Jensey O7O72 U. S. A.
proNEEFt ELECTFTG,NTC (EUFICIPE) N.V.
Mein-centen, Mein 21, 2OOO Antwenp, Belgiurn
Prlnted in Japan
<ARB-081-A>
<73H03E06J>