m Revolutionary AAVA volume control for top performance and superb
sound quality m Fully modular construction with individual left/right
amplifier units arranged on motherboard m Separate powertransformers and filtering capacitors for left and right channels
m Logic-controlled relays for shortest signal paths m High quality
tone controls m Optional analog record playback capability

Innovative AAVA type volume control guarantees great sound and top
performance Experience volume adjustment without deterioration inS/N ratio or distortion. AAVA and other circuit modules are arranged onmotherboard separately for left and right channels. Fully dual monaural
construction features two separate power transformers. Dedicated phonoequalizer unit allows analog record reproduction with superb fidelity.
The C-2400 inherits the design technology of theoutstanding Accuphase C-2800, featuring thesame AAVA type volume control. One of the mostimportant aspects of a preamplifier is how it
handles volume adjustment. AAVA (AccuphaseAnalog Vari-gain Amplifier) is an innovative
concept that differs radically from conventionalvariable-resistor type volume controls.
Amplification and volume control are fully unified,eliminating all mechanical contact points. Pureanalog processing ensures optimum
performance and superb sound. Doing away withthe variable resistor in the signal path has
numerous advantages and brings the amplifiera significant step closer to absolute purity insignal 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 aposition detection method that combines superb
precision with a smooth conventional feel.
The power transformer, filtering capacitors andall other parts of the power supply are duplicatedfor the left and right channel. What's more, allunit 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 theelectrical and the physical plane.
The line amplifier with integrated volume control
is a major aspect of the C-2400, but there arealso a host of other attractive features in thissuperb analog preamplifier. Tone controls andloudness compensator allow fine tuning of thesound. Tape recorder and copying facilities aswell as an EXT PRE function provide connection
flexibility. A phono equalizer unit (AD-2800) for
faithful playback of analog records is alsoavailable.

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 highsignal-to-noise ratio and low distortion of the signal are maintained. The volume can be adjusted without any deterioration in sound quality.

n AAVA resolution
AAVA 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 thecombination of these converter amplifiers is 2 to the powerof 16 = 65,536.

16 current switches(65,536 possible combinations)n AAVA maintains high S/N ratio
With 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 converter
amplifiers (changing the actual gain), there is no change inimpedance 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.

AAVA operation principle

I-V Converter

BUFFER

Reconversion of current intovoltage

INPUT
BUFFEROUTPUT

Input music signal

Currentvalues
areaddedGAINn No more left/right tracking differences orcrosstalkBecause AAVA is an electronic circuit employing highly
precise metal film resistors, there is virtually no left/righttracking error also at low volume levels. Since channels
can be kept separate, crosstalk also does not present aproblem.

n Simple circuit configuration
AAVA unifies the amplifier and volume control functions,
resulting in a circuit that is electrically very simple. Longterm reliability is excellent, with performance and soundquality that will remain unchanged also after prolonged use.

n 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.

VOLUME
54CPU

V- I Converter
Conversion into current with 16
weighting stages (1/2 - 1/216)

VolumeBalance
Attenuator

CPU detects position of volume knob
and operates current on/off switches
according to knob position

637

1

928MINMAX

Volume knob is turned andposition 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, 1/22, ... 1/215, 1/216]. 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, thecombined current is converted back into a voltage by an I-V (current - voltage) converter.

n Same operation feel as a conventional highquality 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 thesame as with a conventional control, and as before,
operation via the remote commander is also possible.

n Attenuator and balance
implemented by AAVAcontrol

also

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 theconfiguration simple helps to maintain high performanceand sonic purity.

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/rightchannel on motherboard

n Supplied remote commander
RC-32
Allows volume control and input
source selection.

Selectable preamplifier gain
The overall gain of the preamplifier
can be set to 12, 18, or 24 dB witha rear-panel switch. This allows theC-2400 to operate at optimum gain
in any kind of system.
Factory default: 18 dB

Logic-controlled relays assure high soundquality and long-term reliabilityThe 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 withseparate power transformers and separateboard-mounted unit amplifiers for left/rightsmoothing capacitors
are also separate for the twostereo channels. This dual monauralapproach assures total freedom from unwanted
mutual interaction.
Tone controls use summing active filters forhighest 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, thecharacteristics are created at F1 and F2 andadded tothe signal, Input
OutputtherebyproducingFthe desired
VRchange.
This design
F
providesVR
efficient
Principle of tone control circuitry
control(summing active filter)without
degrading signal purity.
112

2

The input buffer, AAVA circuit, balanced output
and other amplifier circuitry are configured asfive separate units for each channel, arranged
neatly on a motherboard. Power transformers andn Flexible input/output configurationn Dedicated headphone amplifier
optimized for sound quality
n EXT PRE function allows use of
external preamplifiern Optional phono equalizer allows
playback of analog records
n Supplied remote commander withvolume control functionn Versatile features:m Recording/playback/monitoring facilities
for 2 recorders
m Copy function
m Loudness compensator for fuller bass atlow levels
m Subsonic filter removes ultra low
frequency noisem Phase selectorm AttenuatorDedicated Phono Equalizer Unit AD-2800
Analog records can be reproduced by installing the dedicated phono equalizer unit AD-2800 in a rearpanel slot. The AD-2800 uses printed circuit boards made from Teflon material (glass fluorocarbon resin)
and is housed in a sturdy aluminum case for complete protection against any external interference. Shortest
possible connection between inputs and amplifier circuitry assures outstanding S/N ratio. Highly reliable
DIN connectors are used for connection to main unit.
+BQ13Q1MMQ19Q11Q3InputQ17Q5Q7Q9Q6Q8Q 10Q15Q4Output

Q2MMMMGain:
30/36 dB, switchable
Input impedance: 47 kilohms

MCGain:62/68 dB, switchable
Input impedance: 10/30/100 ohms, switchable

Q20
Q16Q12 MCMCQ14Q18–B✽ The phono equalizer units AD-290 and AD-290V designed for
the Accuphase models C-290 and C-290V can also be used inthe C-2400.
✽ The AD-2800 can also be used in the Accuphase models
C-2800, C-290 and C-290V.

Equalizer
elements

AD-2800

Circuit diagram of phono equalizer
unit AD-2800 (one channel)

DC servo amplifiern Front panel

C-2400 Guaranteed Specifications
Push to open
sub panel[Guaranteed specifications are measured according to EIA standard RS-490. AD stands for“Analog Disc”.] [Specifications are shown for phono equalizer unit AD-2800 installed.]
m Frequency Response

BALANCED/UNBALANCED INPUT: 03 - 200,000 Hz
20 - 020,000 Hz
AD INPUT [MM/36 dB, MC]:20 - 020,000 Hz
AD INPUT [MM/30 dB]:
20 - 020,000 Hz

m Total Harmonic Distortion (for all inputs)+0 –3.0 dB+0, –0.2 dB±0.2 dB±0.3 dB0.005%

m Input Sensitivity, Input Impedance
Input
AD:MM/30 dB INPUT
AD:MM/36 dB INPUTAD:MC/62 dB INPUTAD:MC/68 dB INPUTBALANCED/UNBALANCED

m Rated Output Voltage,
Output Impedancen Rear panel

Input terminal
AD:MM/30 dB INPUT
AD:MM/36 dB INPUTAD:MC/62 dB INPUTAD:MC/68 dB INPUTBALANCED/UNBALANCED

m Maximum Output Level

0
A Input selector
B Function LED indicator
C Volume control
D Power switch
E Output selector
ALLBAL UNBAL OFF

F Bass/Treble controls
G Tone control on/off button
H Phase selector button
I Stereo/mono selector
J Copy button
K Subsonic filter
L MC cartridge load impedance selector
M Equalizer gain selector
MM: 30 dB/36 dB

MC: 62 dB/68 dB

N Recorder switch
O Balance control
P Headphone jack
Q Loudness compensator
R Attenuator
S Line input connectors
TUNER CD LINE 1, 2, 3
T Recorder output/input connectors
U
21 Unbalanced output connectors
U
22 External preamplifier input connectors (unbalanced)
U
23 Gain selector 24 dB 18 dB 12 dB
U
24 CD/LINE balanced input connectors
a Ground b Inverted (–) c Non-inverted (+)
U
25 Balanced output connectors
U
26 External preamplifier input connectors (balanced)
U
27 AC inlet0Remarks
0 This product is available in versions for 120/230 V AC. Make sure that the voltage shown on
the rear panel matches the AC line voltage in your area.
0 The shape of the AC inlet and plug of the supplied power cord depends on the voltage rating
and destination country.

n Supplied accessories:

Input impedance
47 kΩ
47 kΩ
10/30/100 Ω, switchable
10/30/100 Ω, switchable
40 kΩ/20 kΩ

BALANCED/UNBALANCED OUTPUT:
REC (with AD input):2V
252 mV

50 ohms
200 ohms

m S/N Ratio

Expansion slot
for AD-2800

EXT PRE

Sensitivity
For rated output For 0.5 V output
8.0 mV
2.0 mV
4.0 mV
1.0 mV
0.2 mV
0.05 mV
0.1 mV
0.025 mV
252 mV
63 mV

Input shorted, IHF-A weighting
S/N ratio at rated output
95 dB
89 dB
80 dB
75 dB
111 dBBALANCED/UNBALANCED OUTPUT:
REC (with AD input):

S/N ratio (EIA)
91 dB
92 dB
87.5 dB
88.5 dB
108 dB

7.0 V
6.0 V

m LINE Maximum Input Level BALANCED/UNBALANCED INPUT:

6.0 V

m Maximum AD Input Level MM [30/36dB] INPUT:(1 kHz, 0.005% THD)MC [62/68dB] INPUT:

300/150 mV
7.5/3.75 mVm Minimum Load Impedance BALANCED/UNBALANCED OUTPUT:REC:

600 ohms
010 kilohms

m Gain (gain selector: 18 dB)* Gain can be set to 12/18/24 dB
BALANCED/UNBALANCED INPUT ➞ BALANCED/UNBALANCED OUTPUT: 18 dB
UNBALANCED INPUT ➞ REC OUTPUT:0 dB
AD (MM 30/36dB) INPUT ➞ BALANCED/UNBALANCED OUTPUT: 48/54 dB
AD (MM 30/36dB) INPUT ➞ REC OUTPUT:
30/36 dB
AD (MC 62/68dB) INPUT ➞ BALANCED/UNBALANCED OUTPUT: 80/86 dB
AD (MC 62/68dB) INPUT ➞ REC OUTPUT:
62/68 dBm Tone Controls

Turnover frequency and adjustment range
BASS:
300 Hz ±10 dB (50 Hz)
TREBLE: 3 kHz ±10 dB (20 kHz)m Loudness Compensation +6 dB (100 Hz)
m Subsonic Filter

10 Hz: –18 dB/octave

m Attenuator–20 dBm Power Requirements

AC 120 V / 230 V, 50/60 Hz (Voltage as indicated on rear panel)m Power Consumption

33 watts

m Maximum Dimensions

Width 465 mm
Height 150 mm
Depth 403 mm(18-3/8”)(5-7/8”)(15-7/8”)(Depth with AD-2800 installed: 412 mm)
m Weight

17.6 kg (38.8 lbs) net (18.5 kg with AD installed)
23.0 kg (50.7 lbs) in shipping carton

m AC power cordm Audio cable with plugs (1 m)m Remote commander RC-32• Specifications and design subject to change without notice for improvements.

http://www.accuphase.com/G0305Y

PRINTED IN JAPAN 851-0133-00 (AD1)