Accuphase E-460 User manual

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■Power amplifier assembly and output stage with triple
parallel push-pull power MOS-FETs directly mounted to
large heat sink
Line input and output connectors and balanced input connectors
Power MOS-FETs
Filtering capacitors
"EXT PRE" selector
MC/MM selector
Toroidal power transformer
Large speaker terminals
Circuit diagram of E-460 power amplifier
(one channel)
"PHASE" selector
Power amplifier unit with power MOS FETs in triple parallel
configuration delivers ample power: 180 watts/channel into
8 ohms or 260 watts/channel into 4 ohms.
Instrumentation amplifier principle in power amplifier
section allows fully balanced signal paths. Current
feedback design ensures outstanding high-range phase
characteristics, together with further improved MCS+
topology.
Massive high-efficiency toroidal transformer and large filtering capacitors
(33,000 MF x 2) provide ample reserves.
Output phase selectable individually for
each input, with visual indication. When INV
LED is lit, output phase is inverted. When
LED is out, phase is normal.
EXT PRE switch and power amplifier input
connectors allow independent use of power
amplifier section.
Two option board installation slots provide
further versatility. With AD-20 board, MC/MM switching on
E-460 front panel is possible.
Dedicated headphone amplifier optimized for sound quality.
Analog peak power meters for monitoring output levels.
Loudness compensator for enhanced bass at low listening
levels.
Tone controls using active filters for optimum sound quality.
Two sets of large-size speaker terminals accept also Y lugs.
Logic-controlled relays assure high sound quality and long-term
reliability.
Versatile array of inputs with two balanced inputs to shut out external
noise interference.
The successful and long-running E-400 series
from Accuphase has garnered high praise both
in Japan and abroad and is widely regarded as
the pivotal line of high-end integrated
amplifiers. The E-460 represents a model
change from the popular E-450. It incorporates
the sophisticated technological know-how
gained by Accuphase over the years, and
features a further refined AAVA volume control.
It also marks a return to MOS-FET devices in
class A/B integrated amplifier from Accuphase.
Latest circuit topology and strictly selected
parts bring out the hidden potential in each
music source. Rediscover the joys of music
with this high-class integrated amplifier.
AAVA is a revolutionary principle that redefines
the concept of volume control from the ground
up. Unlike the digital approach involving A/D
and D/A processing, it operates purely in the
analog domain for high performance and
ultimate sound. Because the amplification and
volume control tasks are integrated in a single
electronic entity without any variable resistors,
performance and sonic purity do not deteriorate
over the years, providing excellent reliability.
The power amplifier section is built as an
advanced instrumentation amplifier, which
enables fully balanced signal transmission
throughout. Together with the further improved
MCS+ circuit topology and the highly
acclaimed current feedback principle, this
makes for even better electrical characteristics.
In the output stage, high-power MOS-FET
devices renowned for their great sound and
utter reliability are arranged in a triple parallel
push-pull configuration per channel. MOS-
FETs have excellent frequency response and
high input impedance which reduces the load
on the preceding driver stage. They also have
perfect thermal stability. The power supply
features a massive toroidal transformer and
large filtering capacitors, sustaining the high-
quality power output rated at 260 watts x 2 into
4 ohms or 180 watts x 2 into 8 ohms.
(IGH%ND7/HMS)NTEGRATED!MPLIFIERn)NNOVATIVE!!6!VOLUMECONTROL
ANDTRIPLEPARALLELPUSHPULLPOWER-/3&%4ARRANGEMENTINOUTPUTSTAGE0OWER
SUPPLY FEATURING MASSIVE HIGHEFFICIENCY TOROIDAL TRANSFORMER AND LARGE FILTERING
CAPACITORS PROVIDES AMPLE RESERVES FOR HIGH OUTPUT POWER )NSTRUMENTATION
AMPLIFIER PRINCIPLE IN POWER STAGE ENABLES FULLY BALANCED SIGNAL TRANSMISSION
#URRENTFEEDBACKDESIGNCOMBINEDWITHFURTHERIMPROVED-#3TOPOLOGY
■
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Bias
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Bias
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REGULATOR
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Q1
Q3
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Q8
Q6
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Q18 Q20
Q21
Q22
Q23
Q24
Q25
Q26
Q13
Q11 Q15
Q10 Q14
Q12 Q16
MCS＋
Multiple Circuit
Summing
（ ）

■Supplied remote commander RC-200
Allowsvolumeadjustmentand
inputsourceswitching.
■
AAVAvolumecontrolassembly
 withhigherintegrationdensity
 ofcomponentsandcircuitry
■CPU assembly which controls AAVA and various other functions
AAVA operation principle
The music signal is converted into 16 types of weighted current by
V-I (voltage - current) converting amplifiers [1/2, 1/2
2
, ... 1/2
15
, 1/2
16
].
The 16 currents are turned on or off by 16 current switches, and the
combination 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 voltage by an I-V (current - voltage)
converter.
AAVA is a radically different volume control principle that eliminates all variable resistors from the signal path and provides top-notch performance and sound quality.
Because the music signal is not affected by changes in impedance, high signal-to-noise ratio and low distortion are maintained at any volume control setting.
AAVA (Accuphase Analog Vari-gain Amplifier) Volume Control
AAVA configuration in E-460
16 current switches
(65,536 possible combinations)
CPU detects position of volume
knob and operates current on/off
switches according to knob position
Conversion into current with 16
weighting stages (1/2 - 1/2
16
)
Current values
are added
Input music signal
Reconversion of
current into voltage
Volume knob is turned
and position is detected
V- I Converter
#05
2
OUTPUT
INPUT
5-MCS
I-V Converter
6OLUME
"ALANCE
!TTENUATOR
＋
22
23
1
−
1
−
1
−
216
1
−
1
−
215
BUFFER
■Volume control resolution
AAVA adjusts the listening volume by means of 16 weighted V-I converter amplifiers which are
controlled by current switches. The number of possible volume steps set by the combination of these
converter amplifiers is 2 to the power of 16 = 65,536.
■Input buffer amps use 5-MCS topology
One of the factors that have a bearing on possible noise in an AAVA arrangement is the input buffer
design. By connecting five high-performance amps in parallel, excellent S/N ratio is assured.
■AAVA maintains high S/N ratio and uniform frequency response
Unlike with conventional volume controls, AAVA does not introduce a change in impedance at any
volume setting. Consequently, there is no deterioration of S/N ratio, and frequency response remains
totally uniform. The benefits are especially apparent at settings that correspond to normal listening
levels, because the tonal quality is not altered in any way.
■No more left/right tracking differences or crosstalk
Because AAVA is an electronic circuit employing fixed-value resistors, there is virtually no left/right
tracking error also at low volume levels. Since channels can be kept separate, crosstalk also does not
present a problem.
■AAVA means analog processing
The AAVA circuit converts the music signal from a voltage into a current, switches gain by means of
current switches, and then reconverts the current into a voltage. The entire process is carried out in the
analog domain.
■Same operation feel as a conventional high-quality volume control
The volume control knob position is detected by a dedicated CPU which in turn selects the current
switches for AAVA operation. Operating the knob therefore feels exactly the same as with a
conventional control, and as before, operation via the remote commander is also possible.
■Attenuator and balance control also implemented by AAVA
The functions of the attenuator and the left/right balance control are covered by the AAVA circuit as
well, eliminating the need for additional circuit stages. Keeping the configuration simple helps to
maintain high performance and sonic purity.
■Display shows volume level as numeric value
The volume level (degree of attenuation) as set with AAVA is shown as a numeric indication in the
center of the front panel. The indication ranges from MAX (0 dB) to MIN (lowest setting).

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