Audio Database

The

Accuphase C-280L
700,000 yen(February, 1987 release)

Description

The stereo preamplifier to which improvement, such as carrying the full-scale balanced type line amplifier by 2 amplifier composition in C-280, and carrying ten input terminals in it, was added.

In order to realize more balance transmission which corresponded by the transformer etc. conventionally in high quality, the balance transmission line amplifier by 2 amplifier composition which forms an amplifier in the hot and cold side, respectively is carried.
The same complimentary differential push-pull amplification circuit is completely used for each amplifier.
Moreover, it is controlled in four precise volumes (LR channel linkage) which was divided into cold one also about volume as it is completely hot and which stood in a row.

In addition to all the magnification stage Class-A push pulls, a cascode system is promoted further, FET is used for the load side of cascode connection amplifier, and it is asking for little reproduction sound of coloring more by anxious composition which is not, such as base current leak at the time of bipolar transistor use.

direct-current servo system by IC was adopted as all the unit amplifier, and a direct current generated in the output was detected, it returned to the input, and generating of direct-current drift is prevented.
By direct-current servo system and precise design, generating of direct-current drift is made for there almost to be nothing, and all the signal systems from MC input to an output are made direct connection.
Moreover, a base is firmly 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.

In the power-source part, a power transformer for exclusive use is made a right-and-left channel, it takes it, and it has become the mono-construction which became independent electrically, structurally, and completely.
Furthermore, in order to attain low impedance-ization over a broadband, they are a total of six multiple power supply systems which carry a constant-voltage power source for exclusive use for every unit amplifier.
Since unit amplifier and a constant-voltage power-source part are stored by thick aluminum housing and wire connection is carried out by a curtate distance, they have prevented the rise of the power-source impedance in a high region.

Since a straight signal course is constituted at the shortest, a relay is installed in the place of all the required signal courses, and it is changing by a switch controlling these relays electronically in a logic circuit.
Especially the relay currently used has adopted the encapsulated type relay containing [ which was developed as the object for audios, or an object for communication machines ] nitrogen gas, and a contact is a crossbar twin system of gold and a silver palladium alloy, and has become low contact resistance and a thing of high durability which has high quality.
Furthermore, in order to improve reliability more, it is used for a low-level signal course by 4 circuit parallel, and completeness is expected.

The equalizer amplifier part is selecting carefully and using the low noise element for the input stage of differential amplification especially, although a basic circuit is almost the same as that of one side of line amplifier.
The element which makes the RIAA reproducing characteristics which influence sound quality is constituted from a network which combined resistance and a capacitor, and has adopted especially as this portion the silvered mica condenser developed as an object for audios.
This capacitor forms a silver thin film in the refined piece of mica of high purity 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. Moreover, since it is directly connected to the edge portion of a silver film, how to take out the lead which affects sound quality does not have degradation.

In the head amplifier part, low impedance-ization of a NFB loop is attained and resistance noise is decreased at the same time it uses a low noise element for an input circuit.
Moreover, in order to avoid the influence of the noise generated from direct-current servo, it has returned to the base of not only a method but the current generator which returns to the minus side of differential amplification directly. Thereby, the influence of the noise of a servo system was lost mostly, and has realized SN near theoretical full limits.

In order to correspond to various MC cartridges and to be able to control sound quality minutely, MC input impedance is considered so that it may change to a three-stage (10ohm, 30ohm, and 100ohm).
Moreover, the gain changeover switch is provided so that a profit of 32dB may be obtained by everything but a usual head amplifier profit of 26dB for a low output MC cartridge.

It thinks not deteriorating over a long period of time as important, and the jack which performed high-class rhodium plating is specially made to each input jack, and is used for it. Since it has an altitude which is equal also to 100 million slides by 1-micrometer thickness and excels also in corrosion resistance, good contact is maintained over a long period of time.

The Attenuator which leaves volume as it is and can lower volume in an instant is carried.
With a counterclockwise rotation - 3 step rotary system to which a level falls is adopted as -20dB and -30dB by infinity (silent) and a clockwise rotation.

Even if channel balance is made perfect and a listening point shifts, the right-and-left independent type Attenuator type level control which can control the normal position is carried.

The monitor switch which can perform the recording / playback / monitor of a tape recorder is carried.
The Compensation which improves low-pitched sound is carried. The Subsonic Filter is carried.

The profound persimmon wood case is adopted as the panel of a gold tone scratch hair line.


Rear
Internal Volume
Mother The

Rating of a mode
Form Stereo preamplifier
Frequency response
CD, Tuner, Line, Tape Play : 1.0Hz-350kHz+0 -3.0 dB
20Hz-20kHz+0 -0.2 dB
CD, Line (Balanced Input) : 1.0Hz-700kHz+0 -3.0 dB
AD: 20Hz-20kHz+0 -0.2 dB
Input sensitivity/impedance
(Rating / EIA output 0.5V)
AD(Head Amp off): 4.0mV/0.5mV/47kohm
AD (Head Amp+26dB): 0.2mV/0.025 mV/10ohm, 30ohm, 100ohm
AD (Head Amp+32dB): 0.1 mv/0.0125mV/10ohm, 30ohm, 100ohm
CD, Line, Tuner, and Tape:252mV/31.5mV/20kohm
CD, Line(Balanced):252mv/31.5mV/40kohm (20kohm/20kohm)
An Output power/impedance Output(Balanced): 2.0V/50 ohm (25ohm/25ohm), a XLR type connector
Outpput(Unbalanced): 2.0V/1 ohm, a RCA phono jack
Tape Rec: 126mV/200 ohm (at the time of AD), a RCA phono jack
S/N and input conversion noise
Input terminal Input short-circuit IHF-A compensation EIA S/N
Rated input S/N Input conversion noise
AD(Head Amp off): 90dB -140dBV 86dB
AD(Head Amp +26dB): 78dB -152dBV 76dB
AD(Head Amp +32dB): 72dB -152dBV 76dB
CD, Line, Tuner, Tape : 115dB -128dBV 95dB
CD, Line (Balanced) : 115dB -128dBV 95dB
Maximum-except-take-off level
(0.005% of a distortion, 20Hz - 20kHz)
Output(Balanced):10.0V
Output(Unbalanced):10.0V
Tape Rec:19.0V (at the time of AD)
The maximum inlet pressure
(1kHz, 0.005% of distortion)
AD(Head Amp off):300mV
AD(Head Amp +26dB):15mV
AD(Head Amp +32dB):7.5mV
Minimum load impedance Output (Balanced): 600ohms (300ohm/300ohm)
Output(Unbalanced): 1kohm
Tape Rec: 10kohm
Gain CD, Line(Balanced) ->Balanced Output: 18dB
CD, Tuner, Line, Tape Play->Output:18dB
CD, Tuner, Line, Tape Play->Rec Output:0dB
AD(Head Amp Off) ->Output: 54dB
AD(Head Amp Off) ->Rec Output: 36dB
AD(Head Amp+26dB) ->Output: 80dB
AD(Head Amp+26dB) ->Rec Output: 62dB
AD(Head Amp+32dB) ->Output: 86dB
AD(Head Amp+32dB) ->Rec Outpu: 68dB
Loudness Compensation
(Volume control-30dB)
1:+3dB(100Hz)
2: +8dB (100Hz), +6dB (20kHz)
Subsonic Filter 10Hz, -18 dB/oct
Attenuator - 20dB-30dB, -infinity
The semiconductor used Transistor: 219 pieces
FET: 58 pieces
IC: 26 pieces
Diode: 174 pieces
Power source AC100V/117V/220V/240V, 50Hz/60Hz
Power consumption 75W
Dimensions Width 468x height 171x depth of 396mm
Weight 18.1kg