Accuphase E-407, E-407-E Brochure
INTEGRATED STEREO AMPLIFIER
E-407
m Triple parallel push-pull output stage delivers quality power: 180 watts × 2 into 8
ohms m Current feedback principle combines superb sound with total operation stability
m Logic-controlled relays for shortest signal paths m Separator switch allows
independent use of pre/power sections m Large toroidal power tr ansformer m Balanced
inputs m Option board available for playbac k of analog records
State-of-the-art integrated amplifier features current feedback topology
for superb high-range phase fidelity. Wide-range power transistors in
triple parallel push-pull configuration and massive tor oidal transformer
deliver ample power: 260 watts × 2 into 4 ohms, 180 watts × 2 into 8
ohms. Option board enables analog record reproduction in top-notch
quality.
The E-407 represents a new pinnacle of amplifier design. Featuring latest technology and using only the highest quality materials, this integrated stereo amplifier is destined to become a
new reference. Frequency response, S/N ratio,
and all other performance aspects make the
E-407 perfectly suited for the new generation
of ultra high quality program sources such as
SACD and DVD-Audio.
An integrated amplifier provides various advantages such as convenient operation and modest
space requirements. How ev er, because its overall gain is very high, even the slightest interference or crosstalk at the input can have a considerable eff ect on the sonic result. To preclude this
possibility , the E-407 is designed to achiev e total
electrical and structural separation of the
preamplifier and power amplifier sections. These
two parts operate as if they were entirely separate components. A s witch e v en allows using the
preamplifier and power amplifier independently.
Accuphase's highly acclaimed current feedback
topology virtually eliminates phase shifts in the
upper frequency range and assures outstanding
performance and sound quality. The power amplifier output stage employs a triple parallel pushpull configuration, using multi-emitter power tr ansistors designed for high-power audio applications. Ample muscle is provided by the power
supply section which features a massive, highly
efficient toroidal power transformer housed in a
diecast enclosure equipped with heat fins.
In the standard configuration, the E-407 has six
inputs, two of which employ the balanced principle that assures ideal signal transmission characteristics. Provisions f or two tape recorders, with
easy dubbing in both directions, tone controls, and
loudness compensation are further attractive features. An optional analog disc input board allows
reproduction of analog records with outstanding
sonic quality .
The external design of the E-407 continues the
Accuphase tradition, featuring a champagne gold
brushed front panel. Two large power meters in
the center are flanked by the input selector section and the volume control. Not only by virtue of
its excellent sound, from its looks as well the
E-407 is a great addition to any living room.
T riple parallel push-pull output stage delivers
quality power: 260 watts/channel into 4 ohms,
220 watts/channel into 6 ohms or 180 watts/
channel into 8 ohms
The output devices are multi-emitter power transistors designed for high-power audio applications. These de vices hav e excellent frequency response, f orward-current transfer ratio linearity, and
switching performance characteristics. They are
connected in a triple parallel configuration (Figure 1) for low impedance and mounted directly
on a large heat
sink to assure efficient dissipation
of thermal energy .
This allows the E407 to deliver ample power output,
amounting to 260
watts into 4 ohms,
220 watts into 6 ohms, or 180 watts into 8 ohms
per channel.
Current feedback topology in power amplifier
and preamplifier sections guarantees toplevel performance
In the E-407, the signal current rather than the
voltage is used for f eedback. Figure 2 shows the
operating principle of this circuit. At the sensing
point of the feedback loop , the impedance is kept
low and current detection is performed. An impedance-converting amplifier then converts the
current into a voltage to be used as the feedbac k
signal. Since the impedance at the current feed-
Figure 2 Principle of current feedback amplifier
Bias
stabilizer
High-current power transistors
back point (current adder in Figure 2) is very low ,
there is almost no phase shift. Phase compensation can be kept to a minimum, resulting in excellent transient
response and
superb sonic
transparency.
Figure 3 shows
frequency response for different gain settings of the current feedback
amplifier. The graphs demonstrate that response
remains uniform over a wide range.
Discrete-type line amplifier for superior sonic
purity
The line amplifier is entirely built from discrete
parts, to assure optimum performance. Using a
principle developed by Accuphase, a differential
pure complementary push-pull circuit is combined
with a single-ended push-pull emitter follower
output stage. This comparatively simple topology
reduces the need for phase compensation, resulting in effortless, utterly natural and transparent sound.
Highly reliable logic-controlled relays
Program source switching is performed by logiccontrolled relays which are arranged so as to
permit the
shortest possible signal
paths. The
hermetically
sealed relays
are high-quality types developed specifically for demanding communication applications. The contacts are twin crossbar types
plated with gold for minimum contact resistance
and outstanding long-term reliability.
Figure 3 Frequency response with current feedback
(Response remains uniform also when gain changes)
Line amplifier assembly with
current feedback circuitry
Relays connected directly to
gold-plated input/output jacks
Figure 1 Circuit diagram of power amplifier section (one channel)
Tone controls use summing active filters for
pure sound
The tone control circuitry in the E-407 was specially designed with summing active filters. Figure 4 illustrates the operation principle of this cir-
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