Accuphase E 204 Brochure

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13-204

75W/CH REALIZED WITH MOS FETS BUILT-INY SVMMETRICAL, PUSH-PULL HEAD AMPLIFIER
PURE DC AMPS REALIZED WITH DC SERVO CONTROL SCHEME TWO-STEP LOUDNESS COMPENSATOR

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.75W/CH REALIZED WITH MOS FETs

.PUFIE DC AMPS REALIZED WITH DC SERVO CONTROL SCHEME
0 BUILT-IN, SVMMETRICAL, PUSH-PULL HEAD AMPLIFIER
.TWO-STEP LOUDNESS COMPENSATOR

The E-204 is a new 75W/ch high quality Integrated Stereo Amplifier
which received the full benefit of Accuphase's outstanding separate
amplifier design technology in its development, lts powerful output
stage is built around MOS FETs, which are regarded as the best power
amplification devices available. MOS FETs ensure a big improvement
in the brilliance of treble reproduction by eliminating notching distor-
tion. making its low distortion measurements comparable to Class-A
operation characteristics Another big advantage of MOS FETs is their
high durability and heat resistant properties. both important requisites
for devices used in power amplifier applications.

The E-204 employs these superior MOS FETs. about which more
details are given in another section, in a complementary-symmetry
push~pull power output stage that delivers a high quality 75 watts of
power into both channels simultaneously at 8 ohms over a frequency
range of 20 to 20,000 Hz, with less than 0.0l% distortion.

Pure DC amplifiers are used in both the voltage amplifier and power

amplifier sections which permit direct coupling between them to
contribute to improved sound. Employment of DC Servo Control in both
sections further guarantees stable DC operation.

A built-in. 26 dB Head Amplifier in the Preamplifier section makes
possible direct connections of high quality MC (Moving-coil) cartridges
that require the extra amplification boost to bring their levels up to that
of MM (Movingvmagnet) cartridges.

In creating the 5204. a most rigid program of pans selection was
followed to ensure that this amplifier would give forth outstanding
expressive power of music. Rigid parts selection is a basic policy of
Accuphase whose engineers are well aware of the fact that two
amplifiers with identical electrical specifications do not necessarily
produce the same sound, Long experience in the pursuit of perfection
has taught them that high quality parts make the difference in amplifiers
which have that special power to express music more brilliantly. clearly
and impressively.

HI 75W/ch POWER AMP EMPLOYS MOS FETs
AND DC SERVO CONTROL

The power amplifier section employs MOS FETs. the most ideal
device for the power output stage. They deliver a powerful 75 watts
(8-ohm load. both channels simultaneously driven. 20-20000 Hz..
distortion within 0.0l%).

MOS FETs assure a very high quality output signal that is free of
notching and crossover distortions. MOS FETs also have very wide-
band characteristics. which. when fully utilized, prevents harmful TIM
(Transient Intermoduiation Distortion) that occurs when strong dynamic
signals are handled. This is achieved in the E204 by providing a wide
frequency response within the NF (Negative Feedback) loop circuit to
obtain the high speed amplification characteristics necessary to
prevent TIM.

A DC Servo Control system is also employed to stabilize DC amp
operation in the output stage. It effectively prevents DC drift that might
otherwise occur from temperature and/or power supply voltage
fluctuations. and also prevents the flow of DC current and spurious
ultra-low frequency noise into the speakers,

DC SERVO CONTROLLED HIGH-LEVEL
AMPLIFIER SECTION

The lineup of the high-level amplifier section includes the use of dual
FETs in the input buffer stage. followed by a high performance
operational. differential amplifier that feeds a wideband com-
plementary-symmetry final stage. This preamplifier section supplies
amplified. undistorted signal voltages of the highest order to the
following circuits.

Here again. as in the power amplifier section. DC Servo Control is
utilized to prevent DC drift and ensure pure DC operation. This.
together with the use of FETs at the input. has made possible perfect
direct coupling of all sections. all the way from the input to the output
without using coupling capacitors. Sound coloration has thus been
eliminated. giving the E-204 the capability to deliver a more faithful
signal reproduction with improved sound transparency.

3 LOW NOISE, WIDE DYNAMIC RANGE HEAD
AMPLIFIER

The Head Amplifier features push-pull circuitry throughout that
includes a differential push-pull input and a complementary-symmetry
push-pull output.

The input circuit of the Head Amplifier employs ultra»low-noise
transistors in a differential amp circuit. which together with the low
impedance of the NF loop are the reasons for the high S/N ratio of 70 dB
(at rated input). Any type Moving-coil cartridge can be connected
directly without fear of clipping distortion because of the wide dynamic
range of the Head Amplifier (maximum input voltage l0 mV rms).

(Ill
J l, HIGH S/N EOUALIZER AMP

Low noise active devices must be used in the equalizer input circuit
to achieve high S/N ratio. but this alone is insufficient. Low noise parts
and elements must be used as well. Low impedance of the feedback
loop is also most important to obtain low current-noise and thermal-
noise,

Class-A operation with large current flow in the final equalizer
transistors has lowered the impedance of the NF loop. and greatly
reduced the noise generated at the differential input circuit. The S/N
ratio is 77 dB (at rated input) which is close to the theoretical limit.

il
1 \i
TURNOVER SELECTOR SWITCH

A turnover selector switch is provided to expand the tone control
function. This provides selection of 200 Hz and 500 Hz turnover
frequencies for BASS. and 2 kHz and 7 kHz for TFiEBLE. The turnover
selections of 200 Hz and 7 kHz are especially effective for smooth
control over the widest range from the deepest bass to the highest
treble tones. Furthermore. a iO-step detent type control permits
accurate lO-step tonal variations as well as on/off switching of the tone
control circuit.