Accuphase E 305 V Brochure

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DQCUPIWCISG

E305 V

INTEGRATED STEREO AMPLIFIER

0 Output Stage Consisting of 3 Power MOSFET Parallel Push-Pulls
Delivering 130 W/ch (into 8-ohm loads) 0 Low Load Impedance
Design 0 DC Servo Directly Coupling from MC Input to Output
0 Logic Relay Assembly Making Shortest Signal Path

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The EASOSV Integrated Amplifier is the cream of
Accuphase's crop of state-of-theart development
technology. This new Integrated Amplifier was de
veloped based on its predecessor, the E-305. but my
corporates far more sophisticated features than
those of the E7305,

As its name implies, an integrated amplifier com-
bines two amplifiers. a preamplifier and a power
amplifier. into a single chassis, Naturally. this makes
operation easier and saves installation space.
However. it is very diflicult for an integrated amplifier
to achieve the electric characteristics on par with
those of stand-alone amplifiers. The biggest reason
for this difficulty is that the total gain of the inte-
grated amplifier exceeds lOO dB. which can cause
mutual interference and cross talk among internal
units.

However, we. at Accuphase. have finally found a
solution that satisfies even the severest audiophile
demands, Drawing on our tradition of building sep-
aralevtype amplifiers of world renown, we have used
only the finest materials and applied innovative de-
sign to create this new Integrated Amplifier. Conse-
quently. the E~305V has the quality of a stand-alone
preamplifier and power amplifier in an integrated
package

Additionally. the
power amplifier and
the preamplifier of the
E-305V can be used
independently of each
other if so set with a
selector sWitch on the
rear panel

The output stage of
the power amplifier is
made of three parallel
push-pull Circuits per
channel These push-
pull circuits consist of
MOSFETs. Accuphase
has a long tradition of
using power MOS
FETs. In l978, we de-
veloped an integrated
stereo amplifier, the EA
303. using power
MOSFETs for the first

Output stage consisting of 3 parallel push-pull circuits with
power MOSFETs powerfufly driving loads with an impedance
as low as 2 ohms. Complete construction with directly coupled

unit amplifiers. Pure and straight configuration from input to output.
Remote Commander as an accessory. The world can now witness the
emergence of this integrated stereo amplifier with performance

so great that it rivals the quality of stand-alone amplifiers.

time in the world. Since then. Accuphase has intro-
duced many models employing MOSFETs. all of
which have enjoyed an excellent reputation.

A MOSFET has a high input impedance,
Therefore. when MOSFETS are used in the output
stage of an amplifier. the workload of the preceding
stage. the driver stage. is Significantly alleviated. so
that the driver stage can drive the output stage in an
ideal manner. The excellent high-frequency charac-
teristics of the MOSFET offer superb sound quality
and its different atmosphere from that of bipolar
transistor is highly interesting to hifi enthusiasts.
Another notable feature of the MOSFET is the nega-
tive temperature coefficient. This means that the
MOSFET has an excellent environmental durability.
For those reasons. Accuphase has employed
MOSFETs again in creating this new integrated
Amplifier which can deliver 130 watts per channel
into 8ohm loads. 180 watts into 4-ohm loads. and
as much as 250 watts into 2-ohm loads. to addition,
the E-305V is also equipped with a stable. compler
mentary differential push-pull Input circuit. a high»
capacity power transformer. and filter capacitors. to
drive loads With low impedance ratings.

The preamplifier is equipped with a phono equal-
izer amplifier for analog discs so that both MC and
MM cartridges can be used. To linearly amplify the
signals input from such sources as CD players and
tuners. highly stable cascode differential FET input
is used for a high-level amplifier. An independent
regulated power supply circuit is provided to each
of the L and R channels to prevent mutual interfer-
ence among the amplifiers. which would otherwise
occur through the the power supply circuit,

For the volume control. Accuphase has devel-
oped a new potentiometer consisting of. distortion»
free and mirror-like polished rotating resistive
element and a fixed brush. unlike the ordinary po»
tentiometer which is made of a rotating brush and
fixed resistive elements. By fixing the brush. the
number of metal contact points have been reduced.
This contributes significantly to the improvement of
sound quality. In addition. this volume control device
features a gear mechanism and motor. so that it can
be controlled by the Remote Commander supplied
as an accessory. This Remote Commander can also
control the input selector and attenuator. The input
selection is made by gold-clad twin cross-bar relays

lNPUT

Fig. 1 Circuit diagram of power amplifier section

.5.

OUTPUT

.5.

nEcu- s
won 5:

Loudness
compensator
characteristics

which are remote»control|ed with a logic circuit-
another consideration to improve sound quality,

Generally. tone controls are thought to deterioratr
sound quality The tone controls of the E-305Vr-V
however. are of the summing active filter type. which
are also employed in Accuphases Graphic
Equalizer (3-18. With these tone controls. the music
signals do not go through the filter crrcuit. but only
the necessary quantity of the signals are filtered
(summed) to prevent degradation of sound quality.
The loundness compensator ideally performs level
weighting according to the volume

In the Accuphase tradition. the font panel of E-
305V is finished in hair-line polished gold with the
natural persimmon side panels creating warm atmo-
sphere. Large power meters are arranged in the
center of the front panel, flanked by the input selec-
tor to the left and a large volume control knob to the
right for ergonomic conSideration. Switches for less
frequently used functions are arranged behind a
hinged subpanel.

Powerful 3-Parallel Push-Pull Power MOSFET
Output Stage Ideal for Driving Low-Impedance
Loads

Figure 1 shows the circuit desrgn of the E~305V
power amplifier, N-channel power MOSFETs (0.7.
Org. and 0,.) and P-channel power MOSFETs (0.5.
0.3. and 020) are arranged in 3-parallel push-pull
configuration MOSFETs are voltage-controlled
devices. Since the carrier of electrons is different
from that of bipolar transistors. MOSFETs have good
high frequency characteristics and a high switching
speed, The temperature coefficient of a MOSFET is
negative. which means that the drain current does
not increase with temperature, making the MOSFET
free from current concentration and thermal
runaway. Moreover. unlike the bipolar transistor. the
second breakdown does not take place in a
MOSFET in the high voltage region. and therefore.
the MOSFET can guarantee a wide area of safe op
eration.

By using such power MOSFETs in parallel config-
uration. ample power can be supplied to low-impe-
dance loads. Consequently. the E-305V can deliver
130 watts per channel into an 8-ohm loads. 180
watts into a 4-ohm loads. and as much as 250 watts
into 2mm loads.