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
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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