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Extracted text from Accuphase E 450 Brochure (Ocr-read)
The E-450 succeeds the highly popular and
successful Accuphase model E-408. It reﬂ ects
latest research breakthroughs and features
the innovative AAVA-II volume control princi-
ple. Only top-quality parts are used throughout
its sophisticated circuitry. The overall result is
an integrated ampliﬁ er that brings out even
the most delicate nuances in the music with
The AAVA volume control principle developed
by Accuphase totally revolutionizes the way
that the listening volume is adjusted. However,
in its initial form, AAVA required a consider-
able amount of physical space. With AAVA-II,
Accuphase has now taken this principle to the
next level, delivering the same peerless per-
formance in a more compact form factor. This
was made possible by implementing highly
sophisticated surface mount technology while
increasing component density and integration
and optimizing the layout. With AAVA-II, ampli-
ﬁ cation and volume control are fully integrated.
The use of highly reliable electronic compo-
nents eliminates mechanical wear and associ-
ated problems, allowing the control to function
perfectly for many years.
Because an integrated ampliﬁ er has very high
overall gain, even the slightest interference or
crosstalk at the input can have a considerable
effect on the signal provided at the output. To
preclude this possibility, the E-450 is built with
totally separate preampliﬁ er and power ampli-
ﬁ er sections. Both electrically and structurally,
these two parts operate completely autono-
mously. A set of EXT PRE inputs and outputs
allows using the preampliﬁ er and power ampli-
ﬁ er separately. In terms of performance quality,
the E-450 can hold its own even when com-
pared with stand-alone components.
The power ampliﬁ er section is built as an
advanced instrumentation ampliﬁ er, which
enables fully balanced signal transmission
throughout. Together with further improved
MCS+ circuit topology and the highly ac-
claimed current feedback principle, this makes
for even better electrical characteristics. In the
output stage, high-power transistors designed
for audio applications are arranged in a parallel
push-pull conﬁ guration, greatly improving the
capability of the ampliﬁ er to drive low imped-
High-class integrated ampliﬁ er with 180 watts per channel (8 ohms) – Inno-
vative AAVA-II volume control opens up new musical frontiers. High-power
transistors operate in a parallel push-pull arrangement. Power supply with
large, highly efﬁ cient toroidal transformer and oversized ﬁ ltering capacitors
sustains ample power. Instrumentation ampliﬁ er conﬁ guration in power ampli-
ﬁ er makes optimum use of current feedback design combined with further im-
proved MCS+ topology, resulting in excellent high-range phase characteristics.
MCS+ (Multiple Circuit Summing-up)
n Parallel push-pull power ampliﬁ er unit achieves 180 watts
per channel into 8 ohms or 260 watts into 4 ohms.
The output stage devices feature excellent frequency response, current
ampliﬁ cation linearity, and switching characteristics. These high-power
transistors have a rated collector dissipation of 220 watts.
n Instrumentation ampliﬁ er principle in power ampliﬁ er section
allows fully balanced signal paths. Current feedback design
ensures outstanding high-range phase characteristics together with further
improved MCS+ topology.
n Massive high-efﬁ ciency toroidal transformer and large ﬁ ltering capacitor
selected for sound quality provide ample reserves.
n Logic-controlled relays assure high sound quality and long-term reliability.
n Tone controls using active ﬁ lters for optimum sound quality.
n Loudness compensator for enhanced bass at low listening
n E-450 front panel switching enables MC/MM selection for
optional Analog Disc Input Board AD-20.
n “ EXT PRE” button and preampliﬁ er output/power ampliﬁ er
input connectors allow independent use of preampliﬁ er and
power ampliﬁ er sections.
n Dedicated headphone ampliﬁ er delivers audiophile quality
n Analog peak power meters for monitoring output levels.
n Two sets of large-size speaker terminals.
n “High Carbon” cast iron insulator feet further enhance sonic
n Versatile array of inputs with balanced connectors to shut out external
Toroidal power transformer
Large speaker terminals
Unbalanced input/output jacks and balanced input connectors
High-reliability parts selected for sound quality
n Output stage and power ampliﬁ er assembly
with parallel push-pull devices, MCS+ circuit
and current feedback circuitry mounted to
large heat sink Circuit diagram of E-450 power ampliﬁ er
“EXT PRE” button
AAVA-II (Accuphase Analog Vari-gain Ampliﬁ er) type volume control
AAVA-II (Accuphase Analog Vari-gain Ampliﬁ er) is a totally new volume control concept that completely does away with variable resistors in the signal path.
Because the music signal does not have to pass through such devices, there is no adverse inﬂ uence from changes in impedance. This means that the outstanding
S/N ratio and low distortion of the ampliﬁ er are not compromised in any way, and the same superb sound quality will be obtained at any volume setting.
n AAVA-II input stage employs current feedback
principle that ensures high-speed, low-noise
operation and assures excellent characteristics
at high output voltages.
n Volume control resolution.The listening volume is adjusted by a combination of 16 V-I
converters. The number of possible volume steps is 2 to the
power of 16 = 65,536, as determined by current switches.
n AAVA-II circuitry is deceptively simple.Because AAVA-II employs circuitry that is electrically very
simple, long-term reliability is excellent, with performance and sound quality that will remain unchanged also after prolonged
n AAVA-II means analog processing.The AAVA-II circuit converts the music signal from a voltage
into a current, to allow control by current switches, and then
back into a voltage. The entire process is carried out in the
n No more left/right tracking differences or
Because AAVA-II is an electronic circuit employing only ﬁ xed-value
resistors, there is virtually no left/right tracking error also at low
volume levels, and crosstalk also does not present a problem.
n AAVA-II maintains high S/N ratio and uniform
Because AAVA-II does not introduce any change in impedance,
there is no deterioration of S/N ratio or alteration of frequency
response. Changing the volume with AAVA does not mean
introducing noise or otherwise degrading the sound quality of
the ampliﬁ er.
n Control knob gives same operation feel as with
a conventional high-quality volume control.
n Attenuator and balance control also imple-
mented by AAVA-II.
n Supplied remote commander RC-200
Allows volume adjustment and input
V- I ConverterVolume
Conversion into current
with 16 weighting stages
16)CPU detects position of volume knob
and operates current on/off switches
according to knob position16 current switches
(65,536 possible combinations)
addedReconversion of current
Volume knob is turned
and position is detected
principle How AAVA-II works
AAVA-II operates by feeding the music signal to a V-I (volt-
age - current) converting ampliﬁ er where it is weighted in 16
steps [1/2, 1/2
2, ..., 1/2 15, 1/2 16]. The 16 current steps are
turned on or off by 16 current switches, and the combina-
tion of switch settings determines the overall volume. The
switching operation is controlled by a CPU according to the
position of the volume control knob. The combined signal
current forms a variable gain circuit that adjusts the volume.
Finally, the combined current is converted back into a music
signal voltage by an I-V (current - voltage) converter.
n AAVA-II volume control assembly
with higher integration density
of components and