Accuphase C 200 L Brochure

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STEREO CONTROL CENTER

pull circuitry

O Multliunction head amps incorporated I All stage push

0 DC servo controlled throughout 0 All unit amps provided with exclusive regulated power supply

0 SP XLR connectors (balanced output) provided

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The advent of digital recordings (PCM) and
compact discs (CD) reveals a growtng trend
toward digitization of audio equipment In
parallel With this trend, the reproduction capar
bilities of conventional audio devices such as
analog discs and cartridges have shown a
significant amelioration due to the improvement
of record players. amplifiers and other equip-
ment Moreover, the profusnon of Video devices
that can be connected to an audio system has
ushered in an era where multiple program
sources can be used for an audio system.
The C-200L is an advanced Control Center
employing the philosophy of Push-Pull Circuit
ry in every stage" and in addition possesses the
circuitry that was the core of the higher-grade
0280 Series. The basic amplifier circuit is of a
Classt Cascode PushrPull configuration
which provides excellent high-frequency char-
acteristics. linearity. and signal-to-noise ratio,
This baSic amplifier circuit employs a great

CLASS-A CASCODE PUSH-PULL
CIRCUITRV REALIZES IDEAL
AMPLIFIER CIRCUIT

Fig. 1 shows the circuit configuration of the
C-2OOL equalizer and high-level amplifiers.
input field-effect transistor (FET) Q.a serves as
a buffer stage for direct coupling of the am-
plilication stages Combined with transistor 02.
the Ga constitutes a cascode connection. At
the following stage is the Class-A Cascode
Push-Pull Differential amplifier comprising tran-
Sistors 03 through 06 and 09 through 0,2.
Moreover. transistors Q,4 through Qt] also
make up another Class-A Cascode Push-Pull
amplifier that drives the Class-A Darlington
Push»Pull amplifier consisting of 0.9 through
02 at the output stage.

The basic circuit of the cascode connection
amplifier is shown in Fig. 2 As seen. common-
emitter transistor Oi and common-base transis-
tor Q are serially connected as though they
were one element. Because of the low input
impedance of 02, the load impedance of Qi is
accordingly low. assuring stable operations.
The cascode connection amplifier features a
small feedback between the input and output
stages and thereby provides excellent charac-
teristics. especially at a high frequency. Name-
ly. the gain is high. the linearity is maintained up
to the operation limits of the elements, the
distortion is significantly decreased. and the
signal-to-noise ratio is improved. In short, ideal
performance can be expected of a cascade
connection amplifier. but since the cascode
connection amplifier in the C-2OOL consists of
Class-A PushePull circuitry. the characteristics
are even further improved.

With the Classy/X Darlington pair push-pull
circuitry at the output stage. the input impe-
dance can be increased Consequently. the
operations of QM through 017 at the preceding
stage are hardly influenced by the load. realiz-
ing an amplifier with a low distortion and a wide
dynamic range.

number of cascode push-pull Circuits Many of
these basic amplifier circuits are employed
here and there in a unit amplifier The upper-
Iimit characteristics of each unit amplifier is thus
attained,

A total of six unit amplifiers. consisting of
one head amplifier. one equalizer amplifier. and
one highelevel amplifier each on the right and
left channels of the C-200L. constitute the
amplification system. These six unit amplifiers
are completely independent of one another and
each incorporate an exclusive constant-voltage
power supply. The mutual interference between
the unit amplifiers has been thus eliminated and
the stability of each unit amplifier has been
significantly improved.

All stages of the Signal system are directly
coupled by "DC servo system" and thereby
constitute straight DC amplification from MC
input to output.

In addition to an unbalanced type output

Circuit. "BOOrohm balanced type output" is
provided and the output from the OZOOL can
be directly coupled With the balanced input to a
P7600 power amplifier. P»300L power amplifier.
or other audio equipment with balanced type
inputs for commercial purposes.

An additional line input terminal is provided
to keep abreast with the era of multiple program
sources Front Subpanel System is employed
and therefore. the input and output terminals-
are also provided on the front panel

The six independent unit amplifiers are
affixed to a glass epoxy "motherboard" to
assure stable performance This motherboard
is in turn secured to a solid housing of, a
construction highly resistant to VlbfallOnQ

The C-200L can be used as an assoc: d
preamplifier not only for the P-BOOL but all other
power amplifiers.

:2 +B

°2 0: as

01.
INPUT iio owii
1 OUTPUT
05 0n
0:9

or ' 012

4.3-3

Fig. 1 Clrcult Diagram 0! the HIgh-level and Equalizer Amplifier

+8

Output

0 2
Voltage regulator

and
bootstrap ¥ 0

lnputo-

Common base

Or

Common Emitter

Fig. 2 Basic Cascade Amplifier

HEAD AMPLIFIER FOR MC
(MOVING COIL) CARTRIDGE
WITH WIDE DYNAMIC RANGE
REPRODUCES IN EXQUISITE
DETAIL

The head amplifier for use with an MC cartridge
is of sophisticated construction in that an
exclusive amplifier is placed in front of the
equalizer amplifier, The circuit configuration of
the head amplifier is illustrated in Fig. 3. As can
be seen. it consists of three stages: a cascode
push-pull differential. a cascode push-pull cir~
cuit. and a Darlington push-pull circuit. The
signal level of a head amplifier is usually very
low. which is likely to affect the signal-to-noise
ratio. In the C-ZOOL, however. only elements
with a low noise are employed in the circuit
designed with particular consideration given to
decreasing its impedance. thus realizing the
remarkable signal-to-noise ratio. The signals
from the MC cartridge are directly input to

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phenomena may result To realize a straight
and shortest signal path, relays are placed at
locations on the signal path of the C-200L
where a switch is required. These relays are
electronically controlled by a logic circuit to
swnch over inputs. The employed relays are of
airtight type that is exclusively used for audio
equipment and designed to prowde high re-
liability and durability

IMPEDANCE AND GAIN
SELECTORS ENSURE BEST
INPUT MATCHING

The C»2OOL is provided with excellent input
matching to various MC cartridges which come
in such wide variations of impedances and
output levels, For example, output impedances
of MC cartridges vary all the way from 2 ohms
to almost 50 ohms, a difference of 20 or 30
times, Likewise, their output voltage levels vary
from 001 mV to 0 5 mV, 3 difference of 50 times
(34 dB), Although matching MC cartridges to
the head amplifier is not as critical as for
transformer coupling, low output impedance
cartridges should be coupled to low input
impedance to obtain best performance,

To accommodate this wide variety of MC
cartridges and preserve fine control of sound
quality. the C~2OOL provides a chOice of input
impedance of lo ohms, 30 ohms or 100 ohms

This permits coupling MC cartridges of
about S-ohm impedance to a load of 10 ohms
or 30 ohms. and cartridges of over 10-ohm
impedance to either a load of 30 ohms or 100
ohms for closer matching.

Also to accommodate MC cartridges with
very low output levels, a Gain Selector switch in
the C~200L raises the gain to 32 dB instead of
the normally operated head amp gain of 26 dB,

Signal input levels to the head amplifier are
based on RIAA recording characteristics that
drop in the low frequencies and rise in the high
frequency range, A signal at 20,000 Hz would
be about 20 dB, 10 times that of a signal at
1.000 H2, Therefore, the maximum input level of
head amplifiers must extend at least to a level
of 50 mV. ExtenSion is provided up to 150 mV in
the C-200L and this wide dynamic range gives
it ample margin to handle any input pulse signal
voltages,

GOO-OHM BALANCED TYPE
OUTPUT CONNECTOR FOR
LOW NOISE LONG CABLE
CONNECTIONS

The use of a 600-ohm balanced type cable
network has long been a standard practice by
broadcasting stations, and also for commercial
audio applications when long signal carrying
cables are required, since it effectively pre-
vents noise pickup. The C-ZOOL is equipped
with an output connector for connecting such
balanced cables. The principle is shown in Fig,
4 in which equal positive and negative signal
voltages in relation to ground potential are
transmitted by the balanced cable network.
Even if unwanted disturbances are picked up
by the cable, the positive and negative noises
appear in the same phase and are effectively
canceled out by a phase inverted circuit in the

input stage of the power amplifier In short,
such a balanced tine prevents norse pickup
and ensures minimum-deterioration or signal
sound quality from long cable connections
However. the components on both Sides must
be equipped with 600~ohm balanced type
cable connectors.

WIDE TONE CONTROL
CHOICES

Separate tone control circuits are provrded for
the left and right channels Tone is varied with a
10-step rotary switch in 1.5 dB steps The
circuitry also offers switch selection of turnover
frequencies, which further widens tonal varia-
tion choices in the lower and high frequency
ranges with 200 Hz and 500 Hz bass turnover
frequency points, and 2 kHz and 7 kHz treble
turnover frequencies. Also available is an ON
OFF Switch with which the tone control circurtry
can be cut off or activated as desired.

TWO-STEP LOUDNESS
COMPENSATOR

A twostep Loudness Compensator Switch
provides a choice of two sound energy balanc-
ing curves to make up for the deficiency of the
human ear to detect certain audio frequencies

Pre amp, Power amp.

Fig. 4 Principle ol the Balanced Type Network

during low level reproduction. A choice of the
two compensating curves are offered, whose
selection is governed by the sound reproduc-
tion level and listening room acoustics. COMP l
provides a +3 dB boost at 100 Hz COMP 2
provides a +8 dB boosl at 100 Hz and a +6 dB
boost at 20 kHz (With volume set at -30 dB)
The degree of the compensation is automatical-
ly adjusted according to the position of the
VOLUME control

COMPLETE TAPE
RECORDER FUNCTIONS

A total of three tape recorders can be con-
nected to this preamplifier (one to the front Sub
Panel) Any two of these machines can be usel
for tape copying from one machine to another,
This can be done while Simultaneously listening
to a completely different program source since
the Copying SWitch is independent

AMPLE NUMBER OF
INPUT/OUTPUT
CONNECTORS
Plenty of INPUT/OUTPUT connectors are availv
able for convenience in handling a large
number of program sources, and conducting
various tests of sound equipment, A total of
eleven inputs include three pairs of DlSC, one
pair for TUNER. four pairs of LINE and three
pairs of TAPE PLAY connectors, This pream»
plifier also has a total of seven outputs that
include four pairs of OUTPUT connectors, three
pairs of TAPE REC connectors and one head-
phone jack, One pair each of DISC, LlNE, TAPE
PLAY, TAPE REC, and OUTPUT connectors
and a Headphone rack are located on the
frontside Sub Panel for convenience in making
tests, etc. and also to eliminate complexity
The DISC input in the Sub Panel is especially
useful for testing turntables and phone car-
tridges