Audio Database

The

Accuphase C-290V
980,000 yen(December, 1998 release)

Description

Control amplifier which adopted the current feedback magnification circuit, raised the completeness of all the circuits further as a compilation of an analog preamplifier based on the balance transmission technology established by C-290, and aimed at the highest peak.

The current feedback type magnification circuit which returns an output signal in the form of current is adopted.
In this circuit, the impedance of the input terminal by the side of a return was lowered, current was detected, I-V conversion of that current was carried out with the transformer impedance amplifier, and the output signal is made. Since the impedance of a return input portion is very low, it is hard to generate phase rotation and there is almost no necessity for a phase guarantee. For this reason, many characteristics have been sharply improved by a little NFB(s), it excelled in dynamic characteristics, such as a standup, and the natural energy response has been obtained also in respect of sound quality.

The balance output circuit of a bridge feedback system is carried.
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 C-290V, it has a relation of tucking up its sleeves with a cord which feeds back each output of 2 sets of amplifier to the other party, and the symmetrical signal of +- is sent out by low impedance. In this circuit, since floating of the symmetrical signal of +- is 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.

A line amplifier part is a pure complimentary push pull circuit, and constitutes this from a discrete part by a current feedback magnification circuit. Thereby, phase compensation of each stage is made light.

The printed circuit board by a Teflon base (woven glass fabric fluoro-resin) is adopted as a signal transmission circuit.
This material has the lowest relative dielectric constant and dielectric dissipation factor, and heat resistance and the high frequency characteristic are excellent, and it is used for satellite broadcasting, a high precision measuring instrument, etc. which mainly use a super-high-frequency belt.
The propagation velocity of a signal becomes quick, so that the dielectric constant of a printed circuit board is low, and path loss becomes small, so that a dielectric dissipation factor is small. In C-290V, a golden plate is given to a 銅箔 side, and also improvement in sound quality is aimed at.

Right-and-left independence is achieved also with a power transformer and a filter condenser, and it 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 thoroughly.
The amorphous core which was excellent in the frequency response is adopted as a power transformer. Amorphous (Amorphous) serves as amorphous metal which is a synthetic thin strap obtained by super-quenching a Molten metal, and does not have a crystal structure. For this reason, the character which was excellent in magnetic and a machine target compared with crystal structure metal was shown, and it has the characteristic and the feature of having excelled as an object for audios.

Four ream volume in which CP (conductive plastic) element is adopted for the resistance body is adopted in the volume.
When CP resistance object carries out high temperature pressurization fabrication after printing a resistive element, the surface is the low contact resistance and the element of a low distortion which were finished in the shape of a specular surface.
A very thick brass shaft 8mm in diameter is supported by an aluminum cutting bearing, four children's element is stored in a high precision aluminum cutting case, respectively, a perfect shield is given, and improvement in sound quality is aimed at.
A variable system is continuation good transformation, and a tracking error is a position of -60dB and serves as survey of less than 0.5dB.

Since straight signal transmission is constituted at the shortest, the logic relay control system has been adopted.
The sealed type relay for communication industry is adopted as the relay used for this, and contacts are a plated with gold and a crossbar twin system, and have acquired low contact resistance and quantity durability.

The amplifier circuit consists of right-and-left a total of four unit amplifier, such as line-in and a balance output, and carries the exclusive power-source part in each.
In order to prevent that these unit amplifier interferes, it has stored in thick aluminum housing.

In the RCA phono jack, nine lines and a balance input carry three inputs. Moreover, the output is equipped with six lines.

Balance control on either side has adopted the Attenuator of the 1dB step changed to 0 to -6dB, and -infinity with a push button on either side, respectively. It is displayed on the display of a panel side.

In order to correspond also to playback of an analog record, record playback is also supported by extending optional exclusive phone equalizer unit AD-290V from the rear panel side.
The printed circuit board by a Teflon base (woven glass fabric fluoro-resin) is adopted as the quality of the material of a print board, and the influence of external is prevented by storing in a strong aluminum case AD-290V.
Circuit composition consists of all the circuit symmetrical type push pulls, and is equipped with the exclusive input circuit which matched the cartridge of each MM/MC. It constitutes from an FET element of high S/N at the time of MM input, and since MC receives a minute signal by low impedance, it constitutes the difference input circuit by a low noise element, and enables little reproduction of noise.
MC input impedance can choose three kinds. Moreover, a profit can also choose each two MC/MM to compensate for the output of a cartridge. These changes can be performed in respect of the panel of C-290V.

It is possible for phone equalizer unit AD-290 used by C-290 to be compatible, and to use it for C-290V.


Rear The
An
Relay AD-290V

Rating of a mode
The analog disc characteristic shows the time of AD-290V extension.
Form Stereo control amplifier
Frequency response
Balanced, Unbalanced : 3Hz-300kHz+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
Tape 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: 94dB -136dBV 86dB
AD MM/36dB: 90dB -138dBV 86dB
AD MC/62dB: 80dB -154dBV 85dB
AD MC/68dB: 75dB -155dBV 85dB
Balanced: 111dB -123dBV 95dB
Unbalanced 111dB -123dBV 95dB
Maximum-except-take-off level
(Distortion 0.005%, 20Hz - 20kHz)
Balanced, Unbalanced output:8.0V
Tape rec:9.5V
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
Tape rec: 10kohm
Gain 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(62/68dB) input -> Balanced, Unbalanced output: 80/86dB
AD MC(62/68dB) input -> Rec output: 62/68dB
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 24W
The maximum Dimensions Width 469x height 160x depth of 405mm
At the time of AD-290V extension: Depth of 414mm
Weight 23.8kg
At the time of AD-290V extension: 24.8kg
Option Phone equalizer unit AD-290V (200,000yen)