Accuphase C 200 X Brochure

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The Accuphase C-ZOOX is a preamplifier that has wide functional
capabilities befitting its description as a Stereo Control Center, with its
convenient Sub Panel controls and connectors located beneath the front
panel, an Accuphase tradition that was first introduced in our C7200. In
addition, it has a built-in high quality head amplifier for exclusive use with
MC (Moving Coil) cartridges.

Outstanding performance ratings and highest quality are assured by
the C-200X which is based on the Accuphase original complementary-
symmetry. push-pull circuitry enhanced with a further developed Cascode
Bootstrap Differential Push-Pull input stage and new DC Servo Control
circuitry.

Separate unit amplifiers that are plugged in and combined on a
central epoxy glass Motherboard" form the basic scheme of wiring
construction. This system has contributed greatly to its superior and
uniform performance characteristics.

The C-200X features a unique Multiple Power Supply system in which
each unit amplifier for each channel is provided with its own regulated
power supply circuit that completely eliminated interamplifier interference.

The C»200X is a high grade Stereo Control Center which was per-
fected to meet every conceivable requirement befitting its description,
including its use as a standard for comparing preamplifier performance.

m CASCODE BOOTSTRAP COMPLEMENTARY-
SYMMETRY, PUSH-PULL CIRCUITRY

Accuphase amplifiers have traditionally employed the complementary-
symmetry, push-pull circuitry because of its superior basic characteristics
(even before NFB application) and high stability. This original Accuphase
circuitry also produces a clearer. superior and more dynamic sound.

In addition to this basic circuitry. the C-200X also employs a further
developed Cascode Bootstrap Push-Pull Differential Input amplifier.

The diagram below shows the complete circuitry with 01 through 012
forming the input stage. Cascode construction is employed for the input
stage which consists of 0103 and 0204 respectively.The source electrode
of Of connects to the base of 04, after passing through R7, and the source
electrode of 02 connects to the base of 03. after passing through R6, to
form a bootstrap configuration. Likewise. 01109 and 012010 on the
inverting input are connected in similar fashion.

This cascode bootstrap system achieves high gain together with
improved high frequency characteristics. At the same time. it helps to
reduce distortion of high impedance input loads, so it is useful for handling
high impedance MM (Moving Magnet) cartridges. and beneficial in high
level amplifier stages after the volume control. Accordingly, the C<200X
employs this circuitry in its equalizer and high level amplifier sections.

FEEDBACK NETWORK

Cascade Bootstrap construction
of the Equalizer and High-level Amplifiers

/.\
/ PURE DC AMPLIFIER SYSTEM REALIZED
V WITH NEW SERVO CONTROL SCHEME

Since FETs are used at the inputs as shown in the circuit diagram.
direct coupling IS possible for all amplifier stages as long as DC current
flow from temperature and voltage changes are prevented in the output
circuits.

The C-200X employs new type DC Servo Control Systems in its
equalizer amplifiers and tone control amplifiers which have made possible
a pure DC (direct coupled) amplifier system all the way from the Moving
Magnet DISC input to the final output. This has further improved its higher
quality sound reproduction performance. K31 in the circuit diagram indi-
cates the DC Servo amplifier. Its time constant is determined by Ci and
R20. Instead of directly controlling the audio signal path of the differential
amplifier, the output of lCt is used in a new scheme to control the base
currents of 05070608 which function as the source for constant regulated
current. This system minimizes any effect that noise created in the Servo
Control circuit may have on the audio signal path, and also more effec-
tively prevents DC (direct current) drift. Therefore, it assures sup
results when employed in low level, high gain equalizer amplifiers as in
C-ZOOX. A pure DC amplifier system from DISC input to the final output
has been realized together with a significant improvement in reproduction,
thanks to this new DC Servo Control circuit.

5 CLASS-A COMPLEMENTARY-SYMMETRY,
PUSH-PULL HEAD AMPLIFIER

Close attention was paid in desrgning the C-ZOOX to give full play to
the reproductional capabilities of MC (Moving Coil) cartridges. For that
purpose this control center is provided with a differential amplifier system
at the input. and a complementary-symmetry. push-pull output stage that
employs RETs (Ring Emitter Transistors). The former has eliminated the
need for a coupling capacitor at the input, and its harmful effects on
sound quality. It has instead made possible direct coupling of MC car-
tridges to the head amplifier which accounts for a reproduction sound
that is characterized by superior expressive power in revealing musical
details with outstanding clarity.

Only one tonearm is required for both MC and MM cartridges since
the head amplifier is switch controlled for the three inputs. Therefore. MC
and MM cartridges can be interchanged by plug-in process into a
common tonearm.

Circuit Diagram
of the Head Amplifier

HEAVY-DUTY MULTIPLE POWER SUPPLIES

An ideal power supply is one which has low output impedance over
a wide range. and further which absolutely does not affect the charac-
teristics of the amplifier circuitry that it supplies. This means that the
ideal setup between the power supply and unit amplifiers would be direct
connections without lead wires.

With the aim of coming as close to this ideal as possible and elimi-
nating cross interference between amplifier units, the C-200X employs an
extravagant Multiple Power Supply system, It is built around six independ-
ent regulated power supply circuits comprised of RETs and [05, one each
for each head amplifier. equalizer amplifier and high level amplifier of
each left and right channel.

These independent power supply circuits which maintain low im-
pedance over a wide range are positioned strategically very closely to the
respective unit amplifiers that they supply. This has completely eliminated
interference between unit amplifiers. It also accounts for richer bass
reproduction and improved sound focus qualities.