Commentary

Based on the balanced transmission technology established in C-290, a current feedback amplifier circuit is adopted. As a culmination of analog preamp, this control amplifier aims at the highest level by further improving the completeness of all circuits.

It uses a current feedback amplifier circuit that feeds back the output signal in the form of a current.
In this circuit, the impedance of the input terminal on the feedback side is lowered to detect a current, and the current is converted to I-V by a transimpedance amplifier to produce an output signal. Since the impedance of the feedback input part is extremely low, phase rotation hardly occurs, and there is almost no need for phase guarantee. Therefore, various characteristics can be greatly improved with a small amount of NFB, and dynamic characteristics such as rising are excellent, and natural energy response is obtained in terms of sound quality.

It is equipped with a bridge feedback type balance output circuit.
Balanced transmission is a method of simultaneously transmitting positive and negative symmetric signals whose phases are inverted with each other. It has an excellent ability to remove common mode noise components.
In C-290V, the outputs of two pairs of amplifiers are fed back to the other side, and the + - symmetric signal is sent out with low impedance. In this circuit, since the + - symmetric signal is floating from ground, even if one side of the output is grounded, both amplifiers operate and the output voltage does not change.

The line amplifier is a pure complimentary service push-pull circuit and consists of discrete parts using a current feedback amplifier circuit.
This reduces phase compensation at each stage.
The signal transmission circuit uses a printed circuit board made of Teflon (glass cloth fluorine resin).
This material has the lowest relative dielectric constant and dissipation factor, excellent heat resistance and high frequency characteristics, and is used mainly for satellite broadcasting and high-precision measuring instruments using the SHF band.
In printed circuit boards, the lower the dielectric constant, the faster the signal propagation speed, and the smaller the dielectric dissipation factor, the smaller the transmission loss. The C-290V has a gold plate on the copper foil to further improve the sound quality.

The power transformer and filter capacitor are independent on the left and right, and are completely monaural. In addition, all unit amplifiers are equipped with a wide-band low-impedance power supply to prevent interference between amplifiers.
The power transformer uses an amorphous core with excellent frequency characteristics. Amorphous is a composite thin band obtained by ultra-rapid cooling of molten metal. It is an amorphous metal with no crystal structure. As a result, it has superior magnetic and mechanical properties compared with crystal structure metals, and has excellent characteristics and features for audio applications.

The volume is a 4-strand volume that uses a conductive plastic (CP) element as a resistor.
The CP resistor is an element with low contact resistance and low distortion factor whose surface is finished to mirror surface by high temperature pressure molding after the resistance element is printed.
An 8 mm diameter extra-thick brass shaft is supported by an aluminum cutting bearing, and each of the four elements is housed in a high-precision aluminum cutting case for complete shielding to improve sound quality.
The variable method is a continuously variable type, and the tracking error is within 0.5 dB measured at the position of -60dB.

The logic relay control method is used to configure the shortest and straight signal transmission.
The relay used for this is a closed type relay for the communication industry. The contact is gold-plated and crossbar twin system, and low contact resistance and high durability are obtained.

The amplifier circuit consists of a total of four unit amplifiers on the left and right, such as a line input and a balance output, each with its own power supply.
These unit amplifiers are housed in a thick aluminum housing to prevent interference.

Nine NINE RCA-phono jacks for input, a balanced input in the Route 3, and a Route 6 for output.

The left and right balance controls use a 1-dB-step attenuator that can be adjusted from 0 to -6dB and - ∞ with the left and right push buttons, respectively. It appears on the panel display.

In order to play back analog records, a special phono equalizer unit AD-290V (sold separately) is installed from the rear panel side to play back records.
The AD 290 V uses a printed circuit board made of Teflon (glass cloth fluorine resin) and is housed in a sturdy aluminum case to prevent external influences.
The circuit configuration consists of a push-pull circuit with all circuit symmetry. It is equipped with a dedicated input circuit that matches each cartridge of MM/MC. At MM input, it is composed of FET elements with high S/N. Since MC receives minute signals with low impedance, it is composed of a differential input circuit with low-noise elements, enabling low-noise reproduction.
Three types of MC input impedance can be selected, and two types of MC/MM gain can be selected according to the output of the cartridge. These can be switched on the C-290V panel.

It is also compatible with the phono equalizer unit AD-290 used for the C-290 and can be used for the C-290V.

Model Rating

Analog disk characteristics show when AD-290V is added
Type	Stereo Control Amp
Frequency Response	Balanced, Unbalanced : 3 Hz to 300 kHz + 0 -3.0 dB 20 Hz ~ 20 kHz + 0 -0.2 dB AD MM/36dB, MC input : 20 Hz ~ 20 kHz ± 0.2 dB AD MM/30dB input : 20 Hz ~ 20 kHz ± 0.3 dB
Total Harmonic Distortion Factor	0.005%
Input Sensitivity / Impedance (Rated Output / 0.5 v Output)	AD MM/30dB : 8.0mV/2.0mV/47k Ω AD MM/36dB : 4.0mV/1.0mV/47k Ω AD MC/62dB : 0.2mV/0.05mV/10 Ω, 30 Ω, 100 Ω switching AD MC/68dB : 0.1mV/0.025mV/10 Ω, 30 Ω, 100 Ω switching Balanced : 252mV/63mV/40k Ω Unbalanced : 252mV/63mV/20k Ω
Rated Output / Impedance	Balanced, Unbalanced output : 2V/50 Ω Tape rec (at AD input) : 252mV/200 Ω
S/N, input conversion noise	Input Short A - Correction EIA S/N S/N at rated output 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 power level (0.005% distortion rate, 20 Hz to 20 kHz)	Balanced, Unbalanced output : 8.0 v Tape rec:9.5V
AD Maximum Input Voltage (1 kHz, 0.005% distortion)	MM(30dB/36dB) input:300mV/150mV MC(62dB/68dB) input:7.5mV/3.75mV
Minimum Load Impedance	Balanced, Unbalanced output : 600 ohms Tape rec : 10k Ω
Gain	Balanced, Unbalanced input → Balanced, Unbalanced output : 18 dB Unbalanced input → Rec output : 0 dB 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
Compensator (Volume -30dB)	1:+3dB(100Hz) 2 : + 8 dB at 100 Hz, + 6 dB at 20 kHz
Subsonic Filter	10 Hz, -18dB/oct
Attenuator	-20dB
Power Supply	100 VAC, 50Hz/60Hz
Power Consumption	24W
Maximum External Dimensions	469 mm wide x 160 mm high x 405 mm deep When adding AD-290V : Depth 414 mm
Weight	23.8kg When AD-290V is added : 24.8 kg
Sold Separately	Phono equalizer unit AD-290V (¥ 200,000)