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Powerful output stage consisting of parallel push-pull circuits
with MOSFET drive delivers high-quality power
The integrated stereo amplifier E7207 is a further
reﬁned and enhanced version of the predecessor
model E206. lt is based on the same sonic phi-
losophy and design concept. but it delivers an
even higher level of operational ease and perfor-
mance. for perfect harmony with today's demands
ing program sources.
Integrated amplifiers offer considerable ad
vantages regarding space economy. ease of
setup and operation. To realize these advantages
while at the same time delivering performance on
a par with separateatype amplifiers, is no easy
task. since the total gain from the MC input to the
speaker output can be as high as 107 dB lnter»
ference and crosstalk between the various ampli-
fication stages must therefore be avoided by all
means. The E-207 fully reflects Accuphase's long
experience in circuit destgn technology and man-
ufacture of truly outstanding separate amplifiers
of a very high calibre, its electronic circuit design,
physical parts layout, and choice of materials all
work together towards the goal of sonic perfec-
tion, In performance, the E-207 stands heads and
shoulders above other amplifiers in its class. To
do it full justice. it must be compared to the best
performers in the category of separate compo-
The success of the E-207 is based on the thor-
ough separation of the preamplifier section and
power amplifier section. Simply by setting a
switch on the rear panel, these two sections can
be used on their own. Every circuit unit employs
the complementary differential push»pull circuit
design. which is an Accuphase specialty. It is
further enhanced by the DC servo approach.
which allows direct coupling of all amplification
stages and guarantees absolutely stable opera-
The driver stage in the power amplifier section
uses MOSFETs in an original Accuphase. spe-
cially designed Circuit for superior drive charac-
teristics. The power supply features a large power
transformer and amply dimensioned filter capaci-
tors. which let the amplifier handle even low-
impedance loads with ease, Thus, the E-207 can
produce a rated output power of 100 watts per
channel (into 8 ohms. both channels driven). and
even 2thm loads can be driven comfortably,
The preamplifier has a phono section
equipped to handle MM and MC cartridges, The
of 100 watts/ch into 8 ohms.
Outstanding low impedance drive capacity as low as 2 ohms.
All direct-coupled circuitry designed with DC servo
conﬁguration for straight and pure signal transmission
from MC input to speaker outputs.
high-gain phono equalizer provided maintains
superb sound quality for both MM and MC care
tridges. A subsonic filter (-12 dB/oct.. 17 Hz) is
provided to remove any turntable rumble compo,
nents for stable and clean playback.
The input selector has a total of nine positions
4 seven inputs (AD. CD. TUNER. LINE1 , 4) plus
TAPE1 and TAPEZ, The high~gain amplifier
section employs a differential amplifier design
with a FET input stage. Of course. DC servo
control is employed in this section as well. for
totally stable operation.
The four tone controls with center frequencies
of 100 Hz. 500 Hz. 2 kHz. and 8 kHz allow line and
precise adjustments similar to a graphic equal-
izer. An on/off switch lets the user remove the
entire tone control circuitry from the signal path if
The E207 is available in two versions: with the
traditional Accuphase champagne gold face or
with a black faceplate. Optional persimmons
wood side panels further enhance the visual
appeal of this superb amplifier.
Powerful Parallel Push-Pull Output Stage with
Fig. 1 shows the circuit diagram of the power am-
plifier section. 0.3 and 0... form the MOSFET
driver stage in a symmetrical complementary
push-pull configuration. The final stage consists
of the high-performance bipolar transistors 0.5.
0.5. 0.7 and 0.3. each of which has superior elec-
trical characteristics with a cutoff frequency if.) of
70 MHz, a maximum handling current of 10A and
a maximum power dissipation of 100 watts. The
combination of MOSFETs with lop»quality bipolar
devices which works as an excellent voltage con-
troller bringing out the best of both principles for
stable thermal characteristics and efficient high-
The input stage uses a symmetrical arrange-
ment of balanced differential amplifiers in a com-
plete push-pull design. This results in a high
CMFiFi (Common Mode Rejection Ratio) and
notably improves operation stability of direct-
coupled amplifier stages. The first input stage
uses a junction-type FET with outstanding noise
characteristics, to allow minimum input offset and
enables stable direct-coupled operation.
Direct-Coupled Construction with DC Servo
The E-207 has three maior amplifier sections.
namely the phono equalizer, the high-gain and
the power amplifier sections. All of these have
their own DC servo loop and are connected
without any coupling capacitors, for optimum
signal purity. With an improperly designed DC
amplifier. problems such as output voltage drift
clue to temperature influences or output voltage
offset due to component tolerances can impair
operation stability. Therefore. Accuphase em-
ploys the DC servo principle which eliminates all
of these problems and assures stable operation.
From the phono inputs to the speaker outputs.
there are no capacitors in the signal path. result~
ing in impressively clean and uncolored sound.
Sophlstlcated Phono Section for MM and MC
Although digital media are becoming ever more
prominent. the analog records owned by many
audiophiles will be a source of musical pleasure
for many years to come. The E-207 is well
equipped to bring out the best in analog records.
its equalizer section shown in Fig. 2 has dedi—
cated inputs for moving-magnet (MM) and
movmgscoil (MC) cartridges. optimized for their
specific requirements. Since the output voltage
and output impedance of MM cartridges are com-
paratively high, junction FETs (0.. Q?) are used in
a bootstrap differential configuration. The MC
input on the other hand must handle extremely
low-level signals with low impedances, This is
best achieved by a pair of very low—notse bipolar
transistors (05. 05). also in a differential arrange»
ment. In the output of the phono stage. a boot-
Circuit board for preamplifier section
with high-gain equalizer amplifier
Fig. 1 circuit diagram of power amplifier section (one channel)
Fig. 2 Equalizer amplifier section