Audio Database


Accuphase C-275
480,000 yen(October, 1995 release)


Control amplifier which enriched many characteristics further with following the balance transmission technology of C-290, and constituting this from a current feedback magnification circuit.
Although it is pure line amplifier composition, playback of an analog disc is also attained by optional exclusive phone equalizer unit AD-275.

The balance transmission system is used for a line amplifier part.
Balance transmission is a system which sends simultaneously the positive/negative symmetrical signal which the phase reversed mutually, and is excellent in the capability to remove the noise ingredient in the common mode.
In this circuit, it has a relation of tucking up its sleeves with a cord that 2 sets of amplifiers feed back each output to the other party, and the +-symmetrical signal is sent out by low impedance. + Since the symmetrical signal of - is the circuit by which floating was carried out from the ground, even if it grounds one side of an output, both of amplifier operates and an Output voltage does not change.

The balance output unit adopts a current feedback magnification circuit, and constitutes it from a discrete part which thought sound quality as important.
This circuit lowers the impedance of the input terminal by the side of a return, detects current, carries out I-V conversion of that current with a transformer impedance amplifier, and is making the output signal.
In this circuit, since it is hard to generate phase rotation since the impedance of a return input portion is very low, and there is almost no necessity for phase compensation, it excels in the response characteristic over an incoming signal, and power is demonstrated to the music playback containing many pulse ingredients.

The amplifier circuit consists of right-and-left a total of four unit amplifier, such as line-in and a balance output, and was stored in aluminum housing which carries a broadband constant-voltage power source, it was fixed to the mother board of glass epoxy, and the resonance and the mutual intervention by vibration are prevented.
Moreover, a power transformer and a filter capacitor are also considered as right-and-left independence, and electric interference and mechanical vibration are suppressed by having perfect monophonic composition according to the framework structure by the hard aluminum of 8mm thickness.

6N quantity purity copper wire is adopted as a power cord.
Moreover, connection of a commercial cord is also possible by a connector system.

Since a straight signal course is constituted at the shortest, without taking about a signal course, the logic relay control system which controls a relay electronically has been adopted.
The encapsulated type relay for communication industry was adopted as the relay used here, and the contact has acquired low contact resistance and quantity durability by the plated with gold and the crossbar twin system to it.

The phase switch which reverses the phase of the whole equipment is carried.
The change method does not have degradation of sound quality only for replacing + and - of the balance amplifier input unit.

Tone control of the added type active filter system currently used for the full-scale graphic equalizer etc. is adopted as tone control.
A flat [ original ] tone control [ this ] signal is a system which passes straight, is another, makes the characteristic if needed, and is adjusted from a flat signal, and serves as predominance in respect of sound quality.

Amplifier is formed only in headphone.
The output to a speaker can be cut and it can carry out variable [ of the headphone output ] in main volume.

The small resistance object of a distortion is adopted especially as volume.
Volume operation with attached remote control is performed in the combination of this volume controller and a small motor with a clutch.

Each Attached
Input An

Rating of a mode
Form Stereo preamplifier
Frequency response
Balanced/Unbalanced Input: 3Hz-350,000Hz+0 -3.0 dB
20Hz-20kHz+0 -0.2 dB
THD 0.005% (with all the input terminals)
Input sensitivity/input impedance
(An Output power / output 0.5V)
Balanced: 252mV/63mV/40kohm
Unbalanced: 252mV/63mV/20kohm
An Output power/Output load impedance Balanced/Unbalanced Output: 2.0V/50 ohm
Tape Rec (at the time of AD input): 252mV/200 ohms
S/N / input conversion noise Input short-circuit, IEC-A compensation
Maximum-except-take-off level
(0.005% of distortion)
Balanced/Unbalanced Output:6.0V
Tape Rec(at the time of AD input): 6.0V
Minimum load impedance Balanced/Unbalanced Output: 600ohm
Tape Rec: 10kohm
Gain Balanced/Unbalanced Input->Balanced/Unbalanced Output: 18dB
Compensation 1:+3dB(100Hz)
3: +6dB (100Hz), +6dB (20kHz)
Tone control Turnover frequency and variable range
Bass: 300Hz, ±10dB (50Hz)
Treble: 3kHz, ±10dB (20kHz)
Subsonic Filter 10Hz, -18 dB/oct
Attenuator - 6dB-20dB-30dB
Headphone jack Conformity impedance, 4ohm-100ohm
Power supply voltage AC100V
Power consumption 20W
Dimensions At usually, the time: Width 475x height 150x depth of 404mm
At the time of AD-275 extension: Depth of 413mm
Weight At usually, the time: 19.7kg
At the time of AD-275 extension: 20.4kg
Option Exclusive phone equalizer unit AD-275 (\100,000)
Attachment: Remote commander RC-10
Remote control system Infrared pulse system
Power source direct-current3V Battery: UM-4(IEC name R03) 2 piece
The maximum Dimensions Width 66x height 175x depth of 20mm
Weight 190g (Battery included)