Audio Database


Accuphase C-280
680,000 yen(December, 1982 release)


The stereo preamplifier which corresponded to the appearance of the digital audio disc and was developed by the main purpose in an analog and both digital disc playback.

the base before circuit composition's combining dregs coding for retrieval with all the magnification stage Class-A push pulls of Accuphase tradition and giving NFB -- the characteristic is improved.
Since dregs cord connection has little feedback, the good high region characteristic is acquired. Moreover, since a linearity is maintained to the operating limits of an element, distortion decreases and there is a merit of the signal to noise ratio being improved.
Furthermore, a linearity and the distorted characteristic before giving NFB are improved with constituting from a Class-A push pull.

The fundamental circuit composition of unit amplifier is common, and has adopted circuit composition common to head amplifier, equalizer amplifier, and high-level amplifier. The dregs cord push pull by the dregs cord push pull differential amplification of the input by eight elements and four elements consists of three-step magnification fundamentally in two steps of a total of three steps.
Furthermore, direct-current servo circuit by IC was carried, and a direct current generated in the output was detected, it returned to the input, and generating of direct-current drift is prevented. It has become that there is almost nothing about generating of direct-current drift by this direct-current servo system and precise design, and all the signal systems of the output were made direct connection from MC input, and coloring is eliminated.

A power-source part uses a power transformer for exclusive use for a right-and-left channel, and serves as a mono-construction which became independent electrically, structurally, and completely.
Moreover, in order to measure low impedance-ization over a broadband, a constant-voltage power source for exclusive use is carried for every unit amplifier, and it has become a total of six multiple power supply systems. Furthermore, the constant-voltage power-source part of equalizer amplifier constitutes dregs cord differential amplifier, obtains high gain, and is raising the constant-voltage effect.
Unit amplifier and a constant-voltage power-source part have prevented that it is stored by thick aluminum housing, wire connection is carried out by the curtate distance, and power-source impedance becomes high in a high region.

In order to prevent generating degradation of a high region, and an unstable component by taking about a signal course for functions, such as an input change and a tape monitor, it is at C-280,The relay was installed in the place of a required signal course, and the switch controlled these relays electronically and has changed them in the logic circuit.
In this case, the encapsulated type relay containing [ which was developed as the object for audios and an object for communication machines ] nitrogen gas is adopted especially as the relay used, and contacts are golden tension and a crossbar twin system of a silver palladium alloy, and have become low contact resistance and a thing of high durability which has high quality.
Furthermore, in order to improve reliability more, the signal course of a low-level is used by 4 circuit parallel.

In the equalizer amplifier part, low noise-ization is further attained by using the element selected carefully.
The silvered mica condenser developed as an object for audios is adopted especially as a capacitor. This mica condenser forms a silver thin film in the piece of mica of high purity selected carefully by the screen method, and also has special processing and structure of printing a glass pattern (thin glass layer). By this, corposant starting potential becomes high, it is stabilized also in the pulse high voltage, and a signal is passed. Furthermore, how to take out the lead which affects sound quality is considering it as the structure directly connected to the edge portion of a silver film, and has prevented degradation.

The system which inserts exclusive flat amplifier in front of equalizer amplifier is used for the head amplifier for MC cartridges.
Low impedance-ization of a NFB loop is measured at the same time it uses a low noise element for an input circuit, and resistance noise is decreased sharply. Moreover, in order to avoid the influence of the noise generated from direct-current servo, it has returned to the base of the source of low current instead of the method of returning to - side of differential amplification directly, and the influence of the noise of a servo system is suppressed.

Since it corresponds to various MC cartridges, MC input impedance can be changed to a three-stage.
Moreover, the gain changeover switch is also carried for a low output MC cartridge.

The 600-ohm balance type output terminal is carried.

The unit amplifier of a total of six right-and-left channels and a constant-voltage power-source part are stored by thick aluminum housing.
A substrate is fixed with a screw, the output element of Class-A magnification and the element of the constant-voltage power source are being stuck and fixed to housing to serve also as heat dissipation, and resonance by guidance and vibration is prevented.

Two tape recorders are connected and recording, playback, and a monitor are possible.

Three step type rotary type Attenuator is carried, and the change of -20dB-30dB and -infinity is possible.

The right-and-left independent type Attenuator type level level control is carried.
For 0 - -6dB can be correctly adjusted at a 1dB step to -14dB a 0.5dB step and henceforth.

The Subsonic Filter which cuts only the subsonic noise of 10Hz or less is carried.

The Compensation is carried instead of tone control.
It is possible for the position of volume to have rectified the frequency response automatically and to choose two kinds of characteristics with a switch.

The input-and-output jack which performed high-class rhodium plating is adopted, and the outstanding durability has been acquired with the hardness which is equal also to 100 million slides by 1-micrometer thickness.

The front panel and the persimmon wood case of a gold tone scratch hair line are adopted.

Rear Internal

Rating of a mode
Form Stereo preamplifier
Frequency response
Tuner, Line, Tape Play : 1.0Hz-500kHz+0 -3.0 dB
20Hz-20kHz+0 -0.2 dB
Disc: 20Hz-20kHz±0.2dB
THD (new IHF) 0.005% (with all the input terminals, they are 20Hz - 20kHz)
Input sensitivity/impedance
(An Output power / new IHF output 0.5V)
Disc(Head amp off) MM: 2.0mV/0.5mV/47kohm
Disc (Head amp+26dB): 0.1mV/0.025 mV/10ohm, 30ohm, 100ohm
Disc (Head amp+32dB): 0.05mV/0.0125 mV/10ohm, 30ohm, 100ohm
Tuner, Line, and Tape Play:126mV/31.5mV/20kohm
An Output power/impedance Output(unbalanced): 2.0V/1.0 ohm
Output(balanced): 2.0V/600 ohm
Tape rec: 126mV/200 ohms (at the time of Disc)
S/N and input conversion noise
Input terminal Input short-circuit IHF-A compensation EIA S/N
Rated input S/N Input conversion noise
Disc(Head amp off)MM: 85dB -140dBV 82dB
Disc(Head amp +26dB): 72dB -152dBV 76dB
Disc(Head amp +32dB): 66dB -152dBV 76dB
Tuner, Line, Tape Play : 110dB -128dBV 88dB
Maximum-except-take-off level
(0.005% of a distortion, 20Hz - 20kHz)
Tape Rec:19.0V (at the time of AD)
The Disc maximum inlet pressure
(1kHz, 0.005% of distortion)
Disc(Head amp off):300mV
Disc(Head amp +26dB):15mV
Disc(Head amp +32dB):7.5mV
Minimum load impedance Output(unbalanced): 1kohm
Tape Rec: 10kohm
Gain Tuner, Line, Tape Play->output:24dB
Tuner, Line, Tape Play->Tape rec output:0dB
Disc(Head amp off) MM->output: 60dB
Disc(Head amp off) MM->Tape rec output: 36dB
Head amp is +26dB and +32dB change type.
Loudness Compensation
(Volume control-30dB)
2: +8dB (100Hz), +6dB (20kHz)
Subsonic Filter 10Hz, -18 dB/oct
Attenuator - 20dB-30dB, -infinity
The semiconductor used Transistor: 225 pieces
FET: 16 pieces
IC: 33 pieces
Diode: 167 pieces
Power source AC100V/117V/220V/240V, 50Hz/60Hz
Power consumption 75W
Dimensions Width 468x height 171x depth of 396mm
Weight 18.1kg