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Innovative AAVA type volume control Adjusts listening level without
deterioration in S/N ratio or distortion. Dual mono construction with two power
transformers and separate modular AAVA amplifiers for left and right channels
mounted on motherboard. Option board slots provide support for digital input
signals and high-grade analog record playback.
The C-2000 inherits the design technology of
the Accuphase C-2800 and C-2400, featuring
the same AAVA type volume control. AAVA
(Accuphase Analog Vari-gain Amplifier) is an
innovative concept that differs radically from
conventional variable-resistor type volume
controls. It tackles one of the most important
aspects of a preamplifier, namely how it handles
listening level adjustment.
In AAVA, amplification and volume control are
fully unified, eliminating all mechanical contact
points. Pure analog processing ensures
optimum performance and superb sound. Doing
away with the variable resistor in the signal path
has numerous advantages and brings theamplifier a significant step closer to absolute
purity in signal transmission. Another benefit of
AAVA is that it is configured only with highly
reliable semiconductor components. This
assures that performance and sound quality will
remain undiminished for many years to come.
The large volume knob on the front panel
employs a position detection method that
combines superb precision with a smooth
conventional feel.
The power transformer, filtering capacitors and
all other parts of the power supply are duplicated
for the left and right channel. What's more, all
unit amplifiers such as for line input, balanced
output, and AAVA are also entirely separate forthe two channels, arranged on a high-quality
motherboard. This fully monophonic construction
prevents unwanted interaction both on the
electrical and the physical plane.
The line amplifier with integrated volume control
is a major aspect of the C-2000, but there are
also a host of other attractive features in this
superb analog preamplifier. Tone controls and
loudness compensator allow fine tuning of the
sound. Tape recorder and copying facilities as
well as an EXT PRE function provide
connection flexibility. A range of option boards
allows the amplifier to handle digital input
signals and to realize high-grade playback of
analog records.
BUFFER
BUFFER
V- I Converter CPU
OUTPUT INPUT
I -V Converter
Volume
Balance
Attenuator
VOLUME5
46
37
28
19
MIN MAX
The newly developed volume control called AAVA (Accuphase Analog Vari-gain Amplifier) is totally different from conventional controls using
resistors. Because the music signal does not pass through variable resistors, it is not affected by changes in impedance. This means that high
signal-to-noise ratio and low distortion of the signal are maintained. The volume can be adjusted without any deterioration in sound quality.
AAVA operates by feeding the music signal to a V-I (voltage - current) converting amplifier
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 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.
Modular AAVA unit contains
input buffer, 16 V-I converter
amps and current switches,
current adder, I-V converter
amp, and other circuitry on
three boards, plus a CPU for
AAVA control. Modules are
installed separately for left/
right channel on a mother-
board.
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nVolume control resolution
AAVA adjusts the listening volume by means of 16 current
switches which are operated by 16 weighted V-I conver ter
amplifiers. The number of possible volume steps set by
the combination of these converter amplifiers is 2 to the
power of 16 = 65,536.
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nAAVA maintains high S/N ratio and unchanged
frequency response
With conventional volume controls, the impedance
increases significantly at settings that correspond to normal
listening levels, thereby leading to increased noise.
Because there is no change in impedance with AAVA, there
is no deterioration of S/N ratio, and frequency response
also is not affected. Adjusting the volume with AAVA does
not mean introducing noise. High S/N ratio is maintained,
and there is no alteration of sound quality.
n nn n
nNo more left/right tracking differences or crosstalk
Because AAVA is an electronic circuit employing fixed-
value resistors, there is vir tually no left/right tracking error
also at low volume levels. Since channels can be kept
separate, crosstalk also does not present a problem.
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nSimple circuit configuration
AAVA unifies the amplifier and volume control functions,
resulting in a circuit that is electrically very simple. Long-
term reliability is excellent, with performance and sound
quality that will remain unchanged also after prolonged
use.
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nAAVA 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 reconver ts the current into a voltage. The entire
process is carried out in the analog domain.
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nSame 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.
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nAttenuator 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.
AAVA (Accuphase Analog Vari-gain Amplifier) volume control
AAVA principle
Input music
signal
16 current switches
(65,536 possible combinations)
Conversion into current
with 16 weighting stages
(1/2 - 1/2
16) CPU detects position of volume knob
and operates current on/off switches
according to knob position
Reconversion of
current into voltage
Current values
are added
Volume knob is
turned and position is
detected
AAVA operation
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Output
Input
F1
-“A1 -“ A2
VR1
F2
VR2
Response in dB
Frequency in Hz 10 100 1k 10k 100k 16
12
8
4
0
-“4
-“8
-“12
-“16
100Hz BASS TREBLE
40Hz 20kHz 8kHz
Logic-controlled relays assure high sound
quality and long-term reliability
The C-2000 offers a host of input and output
connectors and functions. Strategically placed
relays allow straight and short signal paths, to
prevent degradation that could occur if the signal
had to travel long distances for connection and
function switching.
Dual mono construction with separate power
transformers and separate board-mounted
unit amplifiers for left/right
The input buffer, AAVA circuit, balanced output
and other amplifier circuitry are configured as
five separate units for each channel, arranged
neatly on a motherboard. Power transformers and
smoothing capacitors are also separate for the
two stereo channels. This thorough dual
monophonic approach assures total freedom
from unwanted mutual interaction.
Tone control circuit principle
(using summing active filters)Tone control characteristics
Tone controls use summing active filters for
highest sound quality
The tone control circuitry in the C-2000 uses
summing active filters. The illustration below shows
the operation principle of this circuit. The flat signal
is passed straight through, and only when an
adjustment is required, the characteristics are
created at F
1 and F 2 and added to the signal,
thereby producing the desired change. This designprovides efficient control without degrading signal
purity. The turnover frequency for the bass control
(max. ±8 dB) can be switched between 40 and
100 Hz, and that for the treble control (max. ±8
dB) between 8 kHz and 20 kHz.
nSupplied remote commander RC-20 Allows volume control
and input source
selection.
