Marantz 4070 - Amplifier Block Descriptions; BTL Connection Explained; Pre-Amplifier Stage Details; Balance Control Circuitry and Remote

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The
LR
and
RR
channel
signal
components
are
controlled
by
the
DIMENSION
control
as
shown
below.
DIMENSION control setting
Bottom LF + RF RF +LF
CF
Top LF —RF RF —LF
When the DIMENSION control is set at the bottom the LR and RR channel signals become
monaural, at the center are stereophonic, and at the top are out of phase, thus providing vanished
sound image positioning.
In the SQ DECODER position, ‘“compatible stereo-quadraphonic (SQ) record’’ developed by
CBS is ideally decoded into 4-channel signals. This requires incorporation of the adapter, Model
SQA-1, into the set.
When
the
MONITOR
switch
is
set
to
the
TAPE
position,
signals
from
the
TAPE
1
MON
OUT
terminals
are in
discrete
mode
regardless
of
the MODE
switch
setting.
In
the
SOURCE
position,
the
signals are processed
into
the mode
indicated
by
the
MODE switch
in the
MONO,
2CH,
or
DISCRETE
position
of
the
MODE
switch,
while
signals
remain
in
discrete
mode
in
the
VARI-
MATRIX
and
SOQ
DECODER
positions.
5. BTL (Balanced Transformerless) CONNECTION
This
power
amplifier
is
designed
to
operate
in
either
2-channel
or
4-channel
modes,
depending
on
the
setting
of
the
POWER
MODE
switch
that
incorporates
phase-conversion
and
power
switch
for
BTL
connection.
With
this
switch
placed
in
the
15Wx4
position,
this
unit
operates
as
a
15W
4
channel
amplifier.
With
the
switch
placed
in
the
35Wx2
position,
the
unit
operate
as
a
35W
2
channel
amplifier,
in
which
case,
the
power
output
is
obtained
only
from
FRONT
SPK
terminals.
6. PRE-AMPLIFIER
Mode processed signals are led through the respective VOLUME controls to the TONE
CONTROL circuits. Hi and low frequency response can be varied with the BASS and TREBLE
controls. These controls permit separate adjustment of front stereo pair of channels (LF, RF) and
rear stereo pair of channels (LR, RR).
7. BALANCE CONTROL
Signals passed through the tone controls go into the balance control circuit, in which the
signals are controlled by three balancers: the FRONT L-R, REAR L-R, and FRONT-REAR. By
setting the FRONT-REAR balancer to the “front” side and the FRONT LEFT-RIGHT balancer
to the “‘left’’ side, for example, only the front left (LF) is drived.
The balance control circuit is provided with the REMOTE CONTROL switch which makes
the Model RC-4 Remote Control Box operative when the switch is set in the “REMOTE”
position. In the ““REMOTE” position the balancers on the Model 4070 become ineffective since
signals are led to the Model RC-4. The volume can be varied by the control either on this set or
Model RC-4. At this time, the maximum volume level available by adjustment of the Model RC-4
is not determined by the MASTER VOLUME control on the Model 4070.
8 MAIN AMPLIFIER
The output signals from the balance control circuit are led to the main amplifiers through the
low-pass filter and the high-pass filter circuit. :
Transistors H701 and H703 are the pre-driver coupled to the transistor H713. The transistor
H713 drives the inverter transistors H711 and H713 which, in turn, drive the power stage
consisting of HOO1 and HOO3. Transistors H707 and H709 are current limiter operating as a
power protection circuit.