Audio Database

The

Accuphase C-270V
580,000 yen(April, 1992 release)

Description

preamplifiers only for a high level line, such as CD which the thought and the grade of C-280V were inherited, and it came out, was developed, and was reformed completely at all the points from the founder C-270.

The balance transmission circuit is adopted as a line amplifier part like C-280V. 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.
With the line amplifier of C-280V, it consists of three differential amplifier fundamentally at the time of balance transmission, and amp1 becomes an input and amp2 and amp3 become an output. From +-both the inputs of amp1, a signal enters, and is amplified, and it is inputted into the following amp2 and amp3. 2 sets of these amplifier has a relation of tucking up its sleeves with a cord which feeds back each output to the other party, and sends out the symmetrical signal of +- by low impedance.
Moreover, in making imbalanced connection, the input-and-output side operates normally only by connecting the terminal of either one side to a grand (ground) line.

In C-270V, the line amplifier for a disequilibrium output and the line amplifier for a balanced output are equipped independently, respectively.
With the line amplifier for a disequilibrium output, the input unit is a sauce follower of the constant current load dregs cord bootstrap by all FET, and is amplifying it in the balanced symmetrical type differential push pull emitter earthed circuit with this high phase signal removal ratio. The output unit consists of symmetrical type dregs cord push pull + emitter follower circuits.
With the line amplifier for a balanced output, the balanced output circuit is added to the same exclusive input circuit as disequilibrium output amplifier. this output circuit is the same as that of C-280V -- reversal amplifier and each reversed amplifier -- the bridge feedback which applied feedback to a partner's amplifier constitutes a balance output, and reversal and a reversed output are completely separated from the ground.
direct-current servo is applied to all of these unit amplifier, and, as for the capacitor for a direct-current cut, an input and an output are not inserted.

A power-source part achieves right-and-left independence also with a transformer and a filter capacitor, and has monophonic composition completely electrically. Furthermore, the broadband low impedance power source was carried in all the unit amplifier, and the mutual intervention between amplifier is prevented.

4 linkage volume controller by CP (conductive plastic) element is adopted as the volume which has big influence on sound quality.
CP element currently used as an object for studio is used for the resistance object, and high temperature pressurization fabrication is carried out after printing a resistive element. And the surface of the element was finished in the shape of a specular surface, and low contact resistance and a low distortion are realized.
The brush in contact with a resistance object is a gilding many contact type, is made into an external terminal and solid construction, abolishes a metal-to- metal contact side, and is reducing distortion by different-species metal contacting.
Moreover, a rotary system is considering it as the structure which is not a method which a brush rotates and a resistance object rotates, it decreases sharply, and makes the internal point of contact unnecessary [ contact grease ], and its durability is also improving.
A 極太 brass shaft 8mm in diameter is supported by an aluminum cutting bearing, four elements are stored in a high precision aluminum cutting case, respectively, a perfect shield is given to the case of a tone control machine, and improvement in sound quality is aimed at to it.
A variable system is continuation good transformation and the tracking error has realized survey of less than 0.5dB in a position of -60dB.

The logic relay control circuit is adopted as the change of an incoming signal.
By this system, the high reliability relay was installed in each local, and since the timing of a change is controlled by the logic circuit, it prevented leading about of wiring and has prevented sound quality degradation.
Moreover, the full sealing structure relay containing [ which was developed as an object for audios for - communication machines ] nitrogen gas is adopted especially as a relay, and the contact which influences sound quality has realized low contact resistance and quantity durability with the crossbar twin system of gold and a silver palladium alloy.

C-270V consists of right-and-left a total of six units of the line amplifier for a balanced output divided into the line amplifier for a disequilibrium output, and two units. A print circuit board and the local-area power source which cannot receive interference easily become a pair, and each unit amplifier is stored by thick aluminum housing.
From electric stability or service nature consideration, it is being fixed on the large-sized Mother printed board, and these are being fixed with the chassis by the aluminum material of 8mm thickness so that it may not interfere electrically and mechanically.

The exclusive headphone amplifier of a direct connection system is carried.

The characteristic jack to which rhodium plating was performed is adopted as an input-and-output jack, and outstanding durability is realized.

Three step type Attenuator is carried.

Channel balance is made perfect and the right-and-left independent Attenuator type level control which can control the normal position by arbitrary listening positions is carried. It is possible to adjust for 0 - -6dB to character at intervals of 1dB to -14dB a 0.5dB step and henceforth.
The resistive element has adopted the low distortion type of specular surface finishing.

The phase switch which reverses the phase of the whole equipment is carried.
Since a change system only replaces +- of the balance amplifier input unit and does not have an addition circuit like a phase inversion machine, there is no sound quality degradation.

The Compensation switch which rectifies the shortage of massive at the time of small volume is carried, and the position of a volume controller rectifies the characteristic automatically.

Two tape recorders are connected, and the monitor switch is carried so that recording, playback, and a monitor can be performed.
Balance / imbalanced conversion circuit for exclusive use are equipped so that tape relations can be used in the time of balance as well as the time of unbalance. Moreover, the copy of tape recorders is also possible.
Furthermore, a tuner output is outputted to a tape recorder output terminal also in the time of the power source off of C-270V for absence recording.

The board of natural persimmon finishing is attached to both sides.


Rear
Mother
Unit
Volume
Relay
Rhodium
Internal
It

Rating of a mode
Form Stereo preamplifier
Frequency response
balanced input (CD, Line) : 1.0Hz-300kHz+0 -3.0 dB
20Hz-20kHz+0 -0.2 dB
CD, Tuner, Line, Tape Play : 1.0Hz-300kHz+0 -3.0 dB
20Hz-20kHz+0 -0.2 dB
THD 0.005% (with all the input terminals)
Input sensitivity/impedance
(at the time of an Output power / 0.5V output)
Balanced: 252mV/63mV/40kohm
Unbalanced: 252mV/63mV/20kohm
An Output power/impedance Balanced output: 2.0V/50 ohm
Unbalanced output: 2.0V/1 ohm
Tape rec: 252mV/100 ohms
Headphone jack Conformity impedance: 4ohms - 600ohms
S/N and input conversion noise
Input terminal Input short-circuit IHF-A compensation EIA S/N
Rated input S/N Input conversion noise
Balanced: 110dB -122dBV 94dB
Unbalanced: 110dB -122dBV 94dB
Maximum-except-take-off level
(0.005% of a distortion, 20Hz - 20kHz)
Balanced output:7.0V
Unbalanced output:7.0V
Tape rec:7.0V
Minimum load impedance Balanced output: 600ohms
Unbalanced output: 1kohm
Tape rec: 10kohm
Gain Balanced input->Balanced output: 18dB
Balanced input->Unbalanced output: 18dB
Balanced input->rec output: 0dB
Unbalanced input->Balanced output: 18dB
Unbalanced input->Unbalanced output: 18dB
Unbalanced input->rec output: 0dB
Loudness Compensation
(Volume -30dB)
1:+3dB(100Hz)
2: +8dB (100Hz), +6dB (20kHz)
Attenuator - 20dB-30dB, -infinity
The semiconductor used Transistor: 74 pieces
FET: 36 pieces
IC: 25 pieces
Diode: 97 pieces
Power supply voltage AC100V/117V/220V/240V, 50Hz/60Hz
Power consumption 18W
Dimensions Width 468x height 149x depth of 403mm
Weight 22.0kg