Accuphase E 302 Brochure

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INTEGRATED STEREO AMPUFIER

E-SOZ

I Parallel push-pull output Mags: 120W X 2 (80) a Low impedance speaker
«annulydflven 0 DCservo-comrolledthroughout 0 Signal path
eomolodbyloglc circuit 0 Equlpped with peak power meter

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ECU Pirase

E-302

INTEGRATED ernEo AMPLIFIER

In recent years. an audio system is
increasingly required to have the capa-
bility to cope with not only conventional
LP records but also a variety of other
program sources such as CDs (Com-
pact Discs), digital recorders. broad-
casting satellites._ and so on. In addi-
tion. this diversification of program
sources has made it inevitable that the
audio system must be able to repro-
duce from VTFts and video discs.
Accordingly. an amplifier - an impor-
tant part of an audio system - must be
provided with the ability to amplify the
signals from these various program
sources.

The requisites an amplifier must
meet in this age of mum-program
sources are: the ability of amplifying
signals received from an excellent
program source without degrading
their quality, the function to receive
signals from various program sources,
and excellent operability with due con-
sideration given to human engineering
factors. The E-302 is an integrated
stereo amplifier capable of fulfilling
these requirements. whose specially
important characteristics Accuphase
over the years has polished to their
upper limits through its exclusive.
sophisticated development technology
and by carefully selecting the circuit
elements.

The power output stage of the E-302
employs wide~band, high- power tran-
sistors in parallel push-pull configura-
tion and can produce as high an output
as 120 watts per channel (into 8 ohms.
from 20 to 20.000Hz. with no more
than 0.01% THD). Moreover. ade-
quate consideration is given to the
driving of low-impedance loads and
therefore. a sufficient power can be
output into. for example. a 2-ohm load.
Hence. the E-302 is able to deliver
adequate energy to any type of speak-
ers with the highest stability and fideli-

To make perfection more perfect, so
to speak, our utmost attention was paid
to the use of conventional analog
discs. As a result. the E-302 is provided
with a high-gain equalizer and a selec-
tor switch ior MC (Moving Coil) car-
tridge input impedance that realize the
optimum control of signals input from a
wide range of MC cartridges with ex-
cellent sound quality In addition to
analog discs, tuners. and CDs. three
pairs of line inputs and two pairs of tape
inputs can be connected Thus a total
of eight program sources are connect-
able.

The overall configuration is simple
and straight, without tone control.
Based on human engineering factors.
the front panel when it has the sub-
panel closed, only exposes the volume
control. input selector switches, and
attenuator, to simplify in appearance
the front panel layout.

All unit amplifiers directly coupled in DC servo
configuration. Signal purity preserved from disc
input to output. Design to ensure stable
characteristics even at low load impedance

0 Power Amplifier Unit (Single Channel)

A highquallty power at 120
wansperchannelis
delivered byparallel
push-pull circuitry driven by
aMOSFETdriverstage.
The circuit diagram for the power am,
plilier section is shown in Fig. 1 The
power output stage employs a parallel
push-pull configuration comprising
tour transistors having a Pc (maximum
power dissipation) of 120 watts so that
an adequate power is output (into 8
ohms. 20 to 20.000Hz. with no more
than 0.01 % THD). .The advantage of the
E7302 lies in the driver stage that is the
preceding stage to the power output
stage. As can be seen from Fig. 1. the
driver stage consists of MOS FETs. A
MOS FET is an ideal element for the
driver stage from which a low output
impedance and a high driving voltage
are required. This driver stage. along
with the low emitter resistance in the
output stage. provides extremely high»
quality output. lree of notching distor-
tion.

The input stage of power amplifier
constitutes a bootstrap cascode dif-
ferential amplifier that makes it possible
to obtain excellent high-frequency
characteristics and stability.

Drive MOS FET
Input stage dual FET

Final power transistors

Ic for Dc servo

Drive MOS FET

Final power transistors

Largepawersupplyand

power-tuloutputstagedrive

even Iow4mpedance loads.
The actual impedance of a speaker
fluctuates a lot across the speakers
frequency range. Consequently. the
actual impedance of a speaker system
having a nominal impedance of 4 ohms
may drop to as low as 2 ohms or below
for some frequency ranges On the
other hand. an increasingly large cur-
rent flows through a solidrstate am-
plifier in proportion to decreases in the
load impedance. which may result in
destruction of output transistors.
Hence. the output level for low imped-
ance is severely restricted Neverthe-
less. as digital equipment and devices
are increasingly used In recent years.
the demand for amplifiers that can
supply sufficient power to low-
impedance loads is growmg.

The power amplifier of the E302 has

a highrpower output stage having a Pc
of about 500 watts and is provided with
a large-capacity transformer rated at
700VA. which is quite a high capacity
to be employed in an amplifier of E-
302's class. Thus. an output power as
high as 180 watts per channel has
been realized at a 4-ohm load. Even
when the load impedance is 2 ohms.
sufficient output can be obtained.

A. High-Gain Equalizer
Amplifier Circuit Boar

Directly coupled circuitry
wlthDCservopreserves
signal puritytrom disc Inp
tooutput.
The E-502 employs a virtually ic
configuration in which unit amplifier:
all stages are directly coupled. I
construction guarantees that the or
net signal is amplified and out i
virtually unaltered state to prd ;
extremely high level of fidelity. To el
inate DC drift completely. a probl
that exists in all directly coupled E
piiliers. a powerful DC servo is user
stabilize each unit amplifier.

4

The equalizer amplifier for analog c
employs. as shown in Fig. 2. a sini
amplifier system in which the gair
the high¥gain equalizer amplifier
changed over according to that
quired by an MM (moving magnet
MC (moving coil) cartridge. In this 5
tern. the provision of an amplifying
cuit that can stably operate irrespec
of any quantitative change In t
(negative feedback) and the taking
proper countermeasures against i
iduai noise that may occur when an
cartridge is used are important.
To ensure high stability. the ir
stage of the equalizer amplifier l
ploys a bootstrap cascode differer

High-gain equalizer with
high signal-to-noise ratlr
and MC input impedance
selector switch ensure tl
best use of analog discs.