Accuphase C-2420 User Manual

● AAVA volu me control for h igh performanc e and outstandi ng sound

● Separate power transformers for left and right channels ● Selectable preamp

gain ● Fully modular construction with separate left/right units for each amplifier
stage ● Logic-controlled relays for shortest signal paths ● Independent phase
selectio n for e ach input position ● Optional phono equalizer unit allows
playback of analog records ● Side panels with elegant natural wood finish

Further advanced AAVA volume control elevates performance to a new realm
— A preamplifier for the next generation, featuring AAVA technology
developed for the C-2820. Modular design of AAVA and other amplifier
sections realized in a dual-mono construction with separate power supplies.
Preamplifier overall gain selection setting and phase selection settings for each
input position stored in memory. Numeric indication of volume level. Optional
phono equalizer unit allows playback of analog records with ultimate fidelity.

The Precision Stereo Control Center C-2420 reflects
the refined sonic sensibility of Accuphase while incor­porating advanced technology features developed for
the C-3800 and C-2820. A full model change has fur­ther elevated performance and sound quality to new
heights.
Ever since being first introduced in the C-2800 pream­plifier in 2002, AAVA technology has been continually
refined and improved, while of course retaining the un­derlying principle. The AAVA volume control operates
fully in the analog domain, but it eliminates all potenti­ometers from the signal path. The advantages of this
approach are many: outstanding S/N ratio, extremely
low distortion, no change in frequency response and
sound quality at any listening level, no left/right level
differences or crosstalk, and no other performance re­lated degradations. The conventional concept of
volume control in analog preamplifiers is now well and
truly a thing of the past. Like the C-2820, the new
C-2420 features a high-rigidy, high-precision volume
sensor extruded from a solid aluminum block and
linked directly to the massive volume knob. Both ope­ration feel and accuracy of operation are significantly
improved by this design.
The C-2420 features separate power supplies for left
and right channel, each with a dedicated power trans­former, filtering capacitors and peripheral circuitry. Mod­ular units for the line input, balanced input, AAVA, and
other circuit stages are arranged separately for left and
right channels, to eliminate any risk of unwanted electri­cal or mechanical interaction between the two stereo
channels. A wide variety of versatile functions make the
C-2420 a true control center. There are tone controls
designed for optimum sonic performance, a loudness
compensator, subsonic filter, recorder related functions,
overall preamp gain selection, EXT PRE provision for
use of another preamplifier, individual phase selection
for each input position, and more.
The separately available Phono Equalizer Unit AD-2820
supports both MC and MM cartridges and allows the
reproduction of analog records with utmost fidelity.
Advanced technology enables performance and
sound quality on a level that approaches the realm of
top-of-the-line products. The C-2420 ushers in a new
era of preamplifier excellence.

■

Short and straight signal
paths, along with logic­controlled relays for sig­nal switching assure
high sound quality and
long-term reliability.

■ Versatile arrangement of

line and balanced input

Balanced input and output connectors

and output connectors.

■ EXT PRE function allows use of external preamplifier.

■ Selectable preamplifier gain with three settings (12 dB,

18 dB, 24 dB).

■ 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.

■ Dedicated headphone amplifier ensures great sound and

features two selectable gain settings (standard, +10 dB)
for optimum matching to headphone efficiency.

■ Fully balanced input circuit shuts out external noise.

■ Side panels with beautiful natural wood finish.

■ Tone controls using summing active filters for optimum

sound quality.

■More versatile features:

●

Provisions for recording and playback with a recorder

●

Loudness compensator enhances low end presence

●

Attenuator (-20 dB)

●

Subsonic filter for removing ultra-low-frequency noise

●

Numeric indication of preamplifier overall gain and volume level

6

4

2

0

−

2

−

4

SUBSONICFILTER：ON

−

6

−

8

ResponseindB

−

10

−

12

−

14

−

16

−

18

1     10    100    1k    10k   100k    1M

FrequencyinHz

Frequency Response / Subsonic Filter Characteristics

18

16

14

12

10

ResponseindB

−

−

−

LOUDNESSCOMPENSATOR：ON

8

6

4

2

0

2

4

6

10        100       1k       10k       100k

Loudness Compensator Characteristics

FrequencyinHz

Line input and output connectors

LED indicators for
EXT PRE
function and
phase selector
button

INPUT

Principle of tone control circuitry

(summing active filter)

16

Low

frequency

12

range

8

Boost

4

0

−

4

ResponseindB

−

8

Cut

−

12

BASS TREBLE

adjustment range adjustment range

−

16

10        100       1k       10k       100k

Tone Control Characteristics

FrequencyinHz

Gain selector

High
frequency
range

OUTPUT

C-2420 Block Diagram

−

-

Extruded from solid aluminum block - High-rigidity volume sensor construction

Turning the volume knob on the front panel causes the knob position
to be detected. A corresponding signal is sent to a CPU which in turn
controls the action of the AAVA circuitry accordingly. This vol­ume sensor mechanism was developed by Accuphase
in-house. The massive knob provides a solid
and smooth operation feel and fur­ther enhances position de­tection accuracy.

Interior parts in the

*

image are simulated.

■Supplied remote

commander RC-220

Allows volume

adjustment, input
source switching, and
other operations.

AAVA (Accuphase Analog Vari-gain Amplifier) Volume Control

■Total of 18 V-I converter amplifiers, with dual buffer

amplifiers in input stage for powerful drive capability

The AAVA input stage uses separate buffers for the inverted and

non-inverted side of the balanced input, and features 18 V-I amplifiers,
with the amplifiers for the upper two bits being paralleled for further
improved S/N ratio.

■No more left/right tracking differences or crosstalk

Because the channels can be kept separate, there is virtually no

left/right tracking error also at very low volume levels, and crosstalk
does not present a problem.

■Amplifier display shows accurate gain

When the volume knob is turned, the selected volume level is clearly

indicated by the numeric display on the front panel.

16 current switches
(65,536 possible combinations)

2

3

15

16

＋

BUFFER

INPUT

BUFFER

−

(Music signal)

1
2

1
2

1
2

1
2

1
2

■

AAVA ensures high S/N ratio, low distortion, as well as uni­form frequency response and sound quality at any volume

Because AAVA does not introduce a change in impedance, there is

no deterioration of S/N ratio at any volume setting, and frequency re­sponse remains totally uniform. Therefore the tonal quality is practical­ly not altered.

■Volume control resolution

AAVA adjusts the listening volume by means of 16 weighted V-I convert-

er 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.

■

Attenuator and left/right balance control also implemented by AAVA

Keeping the circuit configuration simple helps to maintain high perfor-

mance and sonic purity.

AAVA configuration in C-2420

I -V Converter

Reconversion of
current into voltage

＋

Current
values are
added

I - V

GAIN

LEVEL DISPLAY

OUTPUT

The music signal is converted into 16 types of weighted current
by V-I (voltage - current) converting amplifiers [ 1/2, 1/2

16

]. The 16 currents are turned on or off by 16 current switches,

1/2
and the combination of switch settings determines the overall
volume. The switching operation is controlled by a CPU to match
the position of the volume control knob. The combined current
forms a variable gain circuit that adjusts the volume of the music
signal. The respective currents are combined and converted back
into a voltage by an I-V (current - voltage) converter.

■High performance and sound quality to last

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.

■AAVA means analog processing

The AAVA circuit converts the music signal from a voltage into a current,
alters 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

Operating the volume knob feels exactly the same as with a conven­tional control, and operation via the remote commander is also possi­ble.

AAVA operation principle

2

, ... 1/215,

V- I Converter

Conversion into current with 16
weighting stages (1/2 - 1/2

16

)

Volume
Balance

CPU

Attenuator

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

Volume knob is turned
and position is detected

AAVAusesaunitamplifierconfigurationcomprisingtheinputbuffer,16V-Iamplifiersandcurrentswitches,cur­rentsummingcircuit,I-Vconverteramplifier,etc.Leftandrightchannelcircuitryiskeptseparateoneachboard.

Phono equalizer amp uses
a dual mono configuration

■Function setting controls on
C-2420 front panel

Dedicated Phono Equalizer Unit AD-2820

Analog records can be reproduced by installing the dedicated phono equalizer unit AD-2820 in a special slot on the rear panel.
The AD-2820 features separate input circuitry for MC and MM cartridges to ensure optimum matching for each cartridge type.
The balanced output stage configuration minimizes noise and ensures highly pure playback. The printed circuit boards are
made from glass cloth fluorocarbon resin and 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.

■MC Gain: 60/70 dB, switchable
Input impedance: 10/30/100/300 ohms, switchable

■MM Gain: 30/40 dB, switchable
Input impedance: 47 kilohms

Q

13

Q

15

Q

16

Q

14

MM

10

MC

MC/MM

INVERTER

Q

5

MM 30 dB

Q

6

MM 40 dB

MC 60 dB

Q

4

AD GAIN

MC 70 dB

EQUALIZER

ELEMENT

MC LOAD

–

Q

7

Q11Q

+

12

Q8Q9Q

Q

2

Q

3

INPUT

Q

1

MM

MC

MC/MM

10Ω

30Ω

100Ω

300Ω

EQUALIZER

ELEMENT

–

+

DC SERVO AMP.

Q

17

Q

18



For information regarding use in other preamplifier models

*

(C-2810, C-2410 etc.), or regarding compatibility with
previous phono equalizer units (AD-2810 etc.), please
contact the Quality Assurance Department of Accuphase.

+ B

Q

19

OUTPUT

Q

20

–

B

AD GAIN selector

■Front panel

MC LOAD selector buttons and LED indicators

Circuit diagram of phono equalizer unit AD-2820 (one channel)

C-2420

Guaranteed specifications are measured according to EIA standard RS-490. AD stands for "Analog Disc".

*

Specifications are shown for phono equalizer unit AD-2820 installed.

*

Gain selector set to 18 dB position.

*

●

Frequency Response

20 - 20,000 Hz +0, -0.2 dB
        AD INPUT (MM/40 dB, MC): 20 - 20,000 Hz ±0.2 dB
       AD INPUT (MC/30 dB): 20 - 20,000 Hz ±0.3 dB

BALANCED/LINE INPUT: 3 - 200,000 Hz +0, -3.0 dB

Guaranteed Specifications

● Total Harmonic Distortion (for all inputs) 0.005%

● Input Sensitivity,

Input Impedance

●

Pressing this button

■Rear panel

AD-2820
installation slot

q Input selector
w Recorder buttons 
e LED function indicators
r Stereo/mono selector button
t Volume control knob
y Power switch
u Output selector
i Bass/treble controls
o Phase selector button
!0 Tone control on/off button
!1 Display on/off button
!2 Subsonic filter
!3 Headphone level selector

ON / PLAY

@1 @2 @3

@5 @7@6 @8

@0 Headphone jack
@1 Line input connectors 
@2 Recorder playback/recording connectors
@3 Line output connectors (2 sets)
@4 EXT PRE input connectors
@5 Balanced input connectors (2 sets)
@6 Balanced output connectors (2 sets)

With line input signal:w negative (-), e positive (+)
With balanced input signal: same phase as source equipment

(Can be switched with phase selector button o )

@7 EXT PRE input connectors (balanced)
@8 AC power supply connector (for supplied power

cord)

opens the sub panel.

@4

★

TUNER / CD / LINE 1, 2 ,3

★

!4 MC load impedance selector button
!5 Balance control
!6 Gain selector 
!7 AD gain selector
!8 Loudness compensator button
!9 Attenuator button

Remarks

★ This product is available in versions for 120/220/230 V AC. Make sure that the voltage shown on the rear panel matches the AC line voltage in your area.
★ 230 V version has an Eco Mode that switches power off after 120 minutes of inactivity.
★ The shape of the AC inlet and plug of the supplied power cord depends on the voltage rating and destination country.

12 dB / 18 dB / 24 dB

■

Supplied accessories

●

Power cord

●

Audio cables with plugs (1 m)

●

Remote commander RC-220

●

Cleaning cloth

Rated Output Voltage,
Output Impedance REC (with AD input): 252 mV 200 ohms

●

Signal-to-Noise Ratio,
Input-converted noise

●

Maximum Output Level

(0.005% THD, 20 - 20,000 Hz)

Maximum LINE Input Level

●

●

Maximum AD Input Level

(1 kHz, 0.005% THD)

●

Minimum Load BALANCED/LINE OUTPUT: 600 ohms

Impedance RECORDER REC: 10 kilohms

● Gain

Gain selector:

LINE INPUT → BALANCED/LINE OUTPUT: 18 dB

（      ）

18 dB

AD [MM: 30/40 dB] INPUT → BALANCED/LINE OUTPUT: 48/58 dB
AD [MM: 30/40 dB] INPUT → REC OUTPUT: 30/40 dB
AD [MC: 60/70 dB] INPUT → BALANCED/LINE OUTPUT: 78/88 dB
AD [MC: 60/70 dB] INPUT → REC OUTPUT: 60/70 dB

      * Gain selector can be set to 12/18/24 dB

● Tone Controls
 BASS: 300 Hz ±10 dB (50 Hz)
 TREBLE: 3 kHz ±10 dB (20 kHz)

Loudness Compensation

●

MC [60/70 dB] INPUT: 9.5/3.2 mV 

● Subsonic Filter 10 Hz: -18 dB/octave

● Attenuator -20 dB

● Headphone Jack Suitable impedance: 8 ohms or higher

Output Level: 2 V (40 ohms)

Power Requirements AC 120 V/220 V/230 V 50/60 Hz (Voltage as indicated on rear panel)

●

●

Power Consumption

Maximum Dimensions

●

Height 150 mm (5-7/8")
Depth 409 mm (16-1/8")
(Depth 414 mm with AD-2820 installed)

● Mass 19.2 kg (42.3 lbs), 20.1 kg (44.3 lbs) with AD-2820 installed

25.0 kg (55.1 lbs) in shipping carton

Input

AD-MM/30 dB INPUT
AD-MM/40 dB INPUT
AD-MC/60 dB INPUT
AD-MC/70 dB INPUT

BALANCED/LINE

BALANCED/LINE OUTPUT: 2 V

Input

AD-MM/30 dB INPUT
AD-MM/40 dB INPUT
AD-MC/60 dB INPUT
AD-MC/70 dB INPUT

BALANCED/LINE

BALANCED/LINE OUTPUT: 7.0 V

RECORDER REC (with AD input): 6.0 V

BALANCED/LINE INPUT: 6.0 V

MM [30/40 dB] INPUT: 310/96.5 mV

BALANCED/LINE INPUT → BALANCED/LINE OUTPUT: 18 dB

Turnover frequency and adjustment range

+6 dB (100 Hz)

34 watts

Width 465 mm (18-5/16")

Input Sensitivity

For rated output

0.25 mV

0.08 mV

Input shorted (A weighting)

S/N ratio at rated output

8.0 mV

2.5 mV

252 mV

For 0.5 V output impedance

0.63 mV

0.063 mV

0.02 mV



94 dB
84 dB
80 dB
72 dB

109 dB

2.0 mV

63 mV

50 ohms

AD-2820 installed

Input

impedance

47 kilohms
47 kilohms

10/30/100/300 ohms, switchable
10/30/100/300 ohms, switchable

40/20 kilohms

EIA S/N

85 dB
85 dB
85 dB
85 dB

107 dB

●

Specifications and design subject to change without notice for improvements.

http://www.accuphase.com

K1205Y PRINTED IN JAPAN 850-2177-00（B1）