Audio Database

The

Accuphase C-2800
1,100,000 yen(July, 2002 release)

Description

Control amplifier which aimed at the highest peak by the engine performance which carries AAVA system volume control as a compilation of an analog preamplifier while raising the completeness of all the circuits further, repeats examination and an audition of part each, and kept being polished to the limit, and sound quality.

The newly developed AAVA (Accuphase Analog Vari-gain Amplifier) system volume control is carried.
This is a volume control system of the completely new concept which does not use a variable resistor object, changes a music signal into voltage -> current, changes current with a switch, controls a gain, and has analog structure again changed into current -> voltage.
The principle of operation has changed the music signal into "1/2, 1/22, ..., 1/215, 1/216", and 16 kinds of current by which dignity attachment was carried out with the V-I transducer. 16 kinds of this current is turned on and off with 16 current switches, respectively, and volume is decided by that combination. By CPU (micro computer), switching control is controlled so that a knob position and volume become the same. Composition of these current serves as Variable Gain Circuit (volume control circuit) which changes the magnitude of a music signal, and also the current compounded in the final stage is returned to voltage with an I-V transducer.
AAVA carries out variable [ of the volume ] by the change of 16 current switches. If 65,536 steps of 16th power = combination of 2 of 16 switches becomes possible and the maximum except take-off makes it 5V, they have the resolving power of a 0.07mV minute signal.
Since there is no generating of the thermal noise from a resistance object in order that a music signal may not pass a variable resistor object, since electronic, and also a music signal is not influenced by impedance, AAVA has the feature that the signal to noise ratio does not change even if it changes volume. Furthermore, there is no distorted influence constitutionally and a super-low distortion is obtained.
Since actual volume operation used the conventional variable resistor and has detected the absolute value for volume in the knob position, it has obtained the conventionally same feeling of operation as volume.

The amplifier circuit of C-2800 consists of right-and-left a total of 18 unit amplifier, such as an input buffer, AAVA, and a balance output, and each unit amplifier is arranged with right-and-left independent composition on the mother board of glass epoxy.
The framework structure by the hard aluminum of 8mm thickness is firmly fixed so that a mutual intervention may not be carried out, and these unit amplifier has prevented electric interference and mechanical vibration.

In order to avoid leading about of a signal course, a logic relay control signal electronic switch is adopted, and the straight signal course is constituted at the shortest.

Newly developed R-toroidal transformer is adopted as a power-source part, and it has at it monophonic composition which made right and left become independent with a filter condenser.
When cross-sectional form is using the circle-shaped core, and R toroidal transformer reduces a magnetic loss and raises efficiency, most leakage flux is lost. Moreover, the exterior uses glass fiber for core material, and has a double case of resin material with high intensity, and 3-fold structure by the epoxy high filler material of vibration proof and adhesion nature.

The printed circuit board by a Teflon base (woven glass fabric fluoro-resin base) is adopted as a signal transmission circuit.
A Teflon base has the lowest relative dielectric constant and dielectric dissipation factor, and is excellent in the high frequency characteristic, and has the feature that heat resistance is also good. In C-2800, a golden plate is further given to a Copper foil
side, and also improvement in sound quality is aimed at.

The gain of a preamplifier part can be chosen by a three-stage.

Sound quality is thought as important and headphone amplifier for exclusive use is built in.

The EXT PRE function in which a change in an external preamplifier is possible is carried.

A Compensation, a phase change function, a function of an Attenuator, a Subsonic Filter, etc. which are compensated with the shortage of massive of low-pitched sound and loud sound are carried.

It is dedicated by the wood case of persimmon finishing.

There is a phone equalizer unit for exclusive use as an option, and it can respond also to playback of an analog record by extending to the rear panel side.
AD-2800 has adopted the Teflon base (woven glass fabric fluoro-resin base), and the influence from the outside is reduced by storing in a strong aluminum case.
Moreover, the magnification circuit was connected with the input terminal by the curtate distance, the signal to noise ratio is improved, and the connector of a reliable DIN standard is adopted as connection with a main part.

It is possible for it to be compatible with C-290, phone equalizer unit AD-290 which were used by C-290V, and AD-290V, and to use it for C-2800.
Moreover, AD-2800 can be used also for C-290 and C-290V.


Rear The
An
An
Logic Phone

Rating of a mode
The analog disc characteristic shows the time of AD-2800 extension.
Form Stereo control amplifier
Frequency response
Balanced, Unbalanced : 3Hz-200kHz+0 -3.0 dB
20Hz-20kHz+0 -0.2 dB
AD MM/36dB, MC input:20Hz-20kHz±0.2dB
AD MM/30dB input:20Hz-20kHz±0.3dB
THD 0.005%
Input sensitivity/impedance
(An Output power / 0.5V output)
AD MM/30dB: 8.0mV/2.0mV/47kohm
AD MM/36dB: 4.0mV/1.0mV/47kohm
AD MC/62dB: 0.2mV/0.05 mV/10ohm, 30ohm, a 100-ohm change
AD MC/68dB: 0.1mV/0.025 mV/10ohm, 30ohm, a 100-ohm change
Balanced: 252mV/63mV/40kohm
Unbalanced: 252mV/63mV/20kohm
An Output power/impedance Balanced, Unbalanced output:2V/50 ohm
Rec (at the time of AD input): 252mV/200 ohms
S/N, input conversion noise
Input short-circuit and A-compensation EIA S/N
At the time of an Output power S/N Input conversion noise
AD MM/30dB: 95dB -137dBV 91dB
AD MM/36dB: 89dB -137dBV 92dB
AD MC/62dB: 80dB -154dBV 87.5dB
AD MC/68dB: 75dB -155dBV 88.5dB
Balanced: 111dB -123dBV 110dB
Unbalanced 111dB -123dBV 110dB
Maximum-except-take-off level Balanced, Unbalanced output:7.0V
Rec(at the time of AD input): 6.0V
The Line maximum inlet pressure Balanced, Unbalanced input:6.0V
The AD maximum inlet pressure
(1kHz, distortion 0.005%)
MM(30dB/36dB) input:300mV/150mV
MC(62dB/68dB) input:7.5mV/3.75mV
Minimum load impedance Balanced, Unbalanced output: 600ohms
Rec: 10kohm
Gain
(Gain switch 18dB position)
Balanced, Unbalanced input -> Balanced, Unbalanced output: 18dB
Unbalanced input -> Rec output: 0dB
AD MM(30/36dB) input -> Balanced, Unbalanced output: 48/54dB
AD MM(30/36dB) input -> Rec output: 30/36dB
AD MC(60/66dB) input -> Balanced, Unbalanced output: 80/86dB
AD MC(60/66dB) input -> Rec output: 62/68dB
* 12 / 18/24dB change is possible for a gain switch.
Compensation
(Volume -30dB)
1:+3dB(100Hz)
2: +8dB (100Hz), +6dB (20kHz)
Subsonic Filter 10Hz, -18 dB/oct
Attenuator -20dB
Power source AC100V, 50Hz/60Hz
Power consumption 48W
The maximum Dimensions Width 477x height 156x depth of 412mm
At the time of AD-2800 extension: Depth of 414mm
Weight 21.2kg
At the time of AD-2800 extension: 22.1kg
Attachment Remote commander RC-32
AC power cord
An audio cable with a plug (1m)
Option Phone equalizer unit AD-2800 (200,000yen)