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Innovative AAVA type volume control guarantees great sound and top
performance Experience volume adjustment without deterioration in
S/N ratio or distortion. AAVA and other circuit modules are arranged on
motherboard separately for left and right channels. Fully dual monaural
construction features two separate power transformers. Dedicated phono
equalizer unit allows analog record reproduction with superb fidelity.
BUFFER
BUFFER
V- I Converter CPU
OUTPUT INPUT
I -V Converter
Volume
Balance
Attenuator
GAIN
VOLUME5
46
37
28
19
MIN MAX
The C-2400 inherits the design technology of the
outstanding Accuphase C-2800, featuring the
same AAVA type volume control. One of the most
important aspects of a preamplifier is how it
handles volume adjustment. AAVA (Accuphase
Analog Vari-gain Amplifier) is an innovative
concept that differs radically from conventional
variable-resistor type volume controls.
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 the amplifiera 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 monaural 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-2400, 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 phono equalizer unit (AD-2800) for
faithful playback of analog records is also
available.
AAVA (Accuphase Analog Vari-gain Amplifier) volume control
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 resolutionAAVA adjusts the listening volume by means of 16 current
switches which are operated by 16 weighted V-I converter
amplifiers. The number of possible volume steps set by the
combination of these conver ter amplifiers is 2 to the power
of 16 = 65,536.
AAVA maintains high S/N ratioWith conventional volume controls, the impedance
increases significantly at settings that correspond to normal
listening levels, thereby leading to increased noise. Because
AAVA performs adjustment by selective use of V-I conver ter
amplifiers (changing the actual gain), there is no change in
impedance and thus no deterioration of S/N ratio. Changing
the volume with AAVA does not mean introducing noise or
detracting from the high performance of the amplifier.
No more left/right tracking differences or
crosstalk
Because AAVA is an electronic circuit employing highly
precise metal film 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.
Simple circuit configurationAAVA 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.
AAVA means analog processingThe 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.
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.
Input music signal16 current switches
(65,536 possible combinations)
AAVA operation principle
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 positionCurrent
values
are
addedReconversion of current into
voltage
Volume knob is turned and
position is detected
AAVA operation principle
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 volume. Finally, the
combined current is converted back into a voltage by an I-V (current - voltage) conver ter.
Input buffer, 16 V-I converter
amps and current switches,
current adder, I-V converter
amp, and other circuitry on
modular AAVA unit, installed
separately for left/right
channel on motherboard
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Selectable preamplifier gain
The overall gain of the preamplifier
can be set to 12, 18, or 24 dB with
a rear-panel switch. This allows the
C-2400 to operate at optimum gain
in any kind of system.
Logic-controlled relays assure high sound
quality and long-term reliability
The C-2400 offers a host of input and output
connectors and functions. Strategically placed
relays prevent any signal degradation that could
occur if the signal has to travel through long paths
for connection and function switching.
Fully dual monaural 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 dual monaural
approach assures total freedom from unwanted
mutual interaction.
Tone controls use summing active filters for
highest sound quality
The tone control circuitry in the C-2400 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 design
provides
efficient
control
without
degrading signal purity.
F1
VR1
F2
VR2
Supplied remote commander
RC-32
Allows volume control and input
source selection.
Factory default: 18 dB
Flexible input/output configuration
Dedicated headphone amplifier
optimized for sound quality
EXT PRE function allows use of
external preamplifier
Optional phono equalizer allows
playback of analog records
Supplied remote commander with
volume control function
Versatile features:
Recording/playback/monitoring facilities
for 2 recorders
Copy function
Loudness compensator for fuller bass at
low levels
Subsonic filter removes ultra low
frequency noise
Phase selector
Attenuator
Principle of tone control circuitry
(summing active filter)
Input Output
