Accuphase C-2400

Commentary

This is a stereo control amplifier with AAVA volume control, inheriting the design technology of C-2800.

The volume control uses the Accuphase Analog Vari-gain Amplifier (AAVA) method.
The AAVA is an analog volume control system that eliminates mechanical contact by integrating the amplifier and volume regulator.
In this method, 16 weighted V-I conversion amplifiers convert music signals into currents. Each of the 16 currents is turned on / off by 16 current switches. The volume is determined by the combination of these switches. The CPU controls the knob position and volume to be the same. In the final stage, the combined signal is converted back to voltage by an I-V converter.
This method eliminates the problem of deteriorating S/N ratio due to impedance changes at the volume position, crosstalk between channels, and left / right volume error, which were problems with conventional volumes.
Because the AAVA is an electronic circuit that integrates an amplifier and volume control, it has a simple electrical structure that minimizes the deterioration of performance and sound quality over time. In addition, because the left and right volume balance and attenuator are also controlled by the AAVA, it has a simple configuration that does not pass through any extra circuits.

The gain of the entire preamplifier can be set from three levels : 12 db, 18 db, and 24 db.

A logic relay control method is adopted for the switching of input / output terminals and functions, suppressing signal routing and realizing the shortest and straight signal path.

The amplifier circuit consists of five unit amplifiers such as input buffer, AAVA and balanced output.
These amplifier circuits are separated to the left and right on the board and placed on the motherboard. The power transformer and smoothing circuit are also separated to the left and right to eliminate mutual interference between the amplifiers.

The tone control circuit uses an additive active filter method.
In this method, a flat signal whose characteristics do not change is made to pass through straight, and the characteristics are made to increase or decrease from the flat signal as required.

Equipped with a headphone amplifier circuit.

Equipped with an EXT-PRE function capable of switching to an external preamplifier.

Equipped with a compensator that increases the volume of the low range.

Equipped with a subsonic filter, ultra-low frequency noise can be cut.

Equipped with a phase switching function.

Equipped with an attenuator function.

Analog playback is possible by adding the phono equalizer unit AD 2800.
The AD-2800 uses Teflon base material (glass cloth fluorine resin base material) and is stored in a sturdy aluminum case to minimize the influence from the outside.
Uses a highly reliable DIN standard connector for connection to the body.
The AD 2800 allows 2-stage gain switching for both MM and MC, and 3-stage impedance switching for the MC position.
* AD-2800 can be used for C-2800, C-290 and C-290V.

The C-2400 is also compatible with the AD-290/AD-290V phono equalizer units used on the C-290/C-290V.

Remote Commander RC-32 is included.
This remote control can adjust the volume and switch the input selector.

Model Rating

Type	Control amplifier
* AD characteristics are when AD 2800 is added.
Frequency characteristic	Balanced/Unbalanced input 3 Hz ~ 200 kHz + 0 -3.0 dB 20 Hz ~ 20 kHz + 0 -0.2 dB AD input (MM/36dB, MC) : 20 Hz to 20 kHz ± 0.2 dB AD input (MM/30dB) : 20 Hz to 20 kHz ± 0.3 dB
Total harmonic distortion factor	0.005% (at all input terminals)
Input Sensitivity / Impedance	Balanced : 252 mv (Rated Output) / 63 mv (0.5 v Output) / 40k Ω Unbalanced : 252 mv (rated output) / 63 mv (0.5 v output) / 20k Ω AD MM (30 db) : 8.0 mv (Rated Output) / 2.0 mv (0.5 v Output) / 47k Ω AD MM (36 dB) : 4.0 mV (Rated Output) / 1.0 mV (0.5 V output) / 47k Ω AD MC (62 dB) : 0.2 mV (Rated Output) / 0.05 mV (0.5 V output) / 10 Ω / 30 Ω / 100 Ω switching AD MC (68 dB) : 0.1 mV (Rated Output) / 0.025 mV (0.5 V output) / 10 Ω / 30 Ω / 100 Ω switching
Rated Output / Impedance	Balanced/Unbalanced output : 2V/50 ohm Rec (at AD input) : 252mV/200 Ω
Signal-to-noise ratio	Balanced : 111 dB (input short, IHF-A at rated output) / 108 dB (EIA) Unbalanced : 111 dB (input short, IHF-A at rated output) / 108 dB (EIA) AD MM (30 dB) : 95 dB (at input short, IHF-A, rated output) / 91 dB (EIA) AD MM (36 dB) : 89 dB (input short, IHF-A, at rated output) / 92 dB (EIA) AD MC (62 dB) : 80 dB (input short, IHF-A, at rated output) / 87.5 dB (EIA) AD MC (68 dB) : 75 dB (input short, IHF-A, at rated output) / 88.5 dB (EIA)
Input equivalent noise (input short, IFF-A)	Balanced:-123dBV Unbalanced:-123dBV AD MM(30dB):-137dBV AD MM(36dB):-137dBV AD MC(62dB):-154dBV AD MC(68dB):-155dBV
Maximum output level	Balanced/Unbalanced output:7.0V Rec (at AD input) : 6.0 V
Line Maximum input voltage	Balanced/Unbalanced input:6.0V
AD Maximum Input Voltage (1 kHz, 0.005% Distortion)	MM(30dB/36dB)input:300mV/150mV MC(62dB/68dB)input:7.5mV/3.75mV
Minimum load impedance	Balanced/Unbalanced output : 600 Ω Rec : 10k Ω
Gain	Gain Switch : 18 db Position (12dB/18dB/24dB switchable) Balanced/Unbalanced input - Balanced/Unbalanced output : 18 db Unbalanced input - Rec output:0dB AD(MM:30dB/36dB) input - Balanced/Unbalanced output:48dB/54dB AD(MM:30dB/36dB) input - Rec output:30dB/36dB AD(MC:62dB/68dB) input - Balanced/Unbalanced output:80dB/86dB AD(MC:62dB/68dB) input - Rec output:62dB/68dB
Tone control	Bass : ± 10 dB (50 Hz), Turnover frequency 300 Hz Treble : ± 10 dB (20 kHz), Turnover Frequency 3 kHz
Compensator	+6dB(100Hz)
Subsonic filter	10Hz:-18dB/oct
Attenuator	-20dB
Pwer	100 VAC, 50Hz/60Hz
Power consumption	33W
Maximum external dimensions	Width 465x Height 150x Depth 403 mm When AD 2800 is added : Depth 412 mm
Weight	17.6kg When adding AD-2800 : 18.6 kg
Attachment	Remote Commander RC-32 AC power cord Audio cable with plug (1m)
Sold Separately	Dedicated Phono Equalizer Unit AD-2800 (¥ 200,000)