Commentary

Stereo preamplifier following the flow of C-280.
The sound quality is transparent and emphasizes the texture of the original sound field.

The circuit configuration is all stage cascode A class push-pull configuration to improve the element characteristics before NFB is applied.
The cascode method combines two amplifying elements in a column and operates as a single element. It increases the input impedance and gain, and at the same time greatly improves the high-frequency characteristics.
Linearity is also maintained up to the operating limit of the device, reducing distortion and improving the signal-to-noise ratio.

DC servo system is used for all unit amplifiers.
It detects the direct current generated at the output and returns to the input, so that the output correctly maintains the 0 potential.
As a result, all signal systems from the input to the output of the analog disk (AD) are directly connected, and high-quality playback sound without coloring is obtained.

It is equipped with a power transformer for the left and right channels, and is supplied by a winding for each unit amplifier.
In order to provide a pure and powerful power supply, we have adopted a multiple power supply system that passes through a constant voltage power supply for each unit amplifier. The rectifier and filter capacitor are placed near the transformer. However, the constant voltage power supply circuit is housed in the housing together with the unit amplifier, successfully keeps the source impedance low over a wide range.

In order to configure the shortest and straight signal path, relays are installed in the signal path where switching is necessary, and these relays are controlled electronically by logic circuits for switching.
The relay uses a sealed type relay developed especially for audio equipment. The contact is a crossbar twin system with high quality, low contact resistance and high durability.

Since the signal level of an equalizer amplifier is very weak, it is easily affected by inherent noise. Therefore, a low-noise FET is selected as the input FET.
In addition, the capacitor uses a compound dielectric non-inductive type, which was developed especially for audio with an emphasis on sound quality. Since it is non-inductive, it has excellent characteristics outside the audible band. Moreover, it is filled with epoxy resin to prevent self-vibration caused by signal voltage.
The feedback resistor uses a metal foil ultra-precision type. In addition to the precision, the resistance value hardly changes with temperature, and stable playback sound can be expected.

Six left and right amplifiers, including a balance amplifier, are enclosed in a thick aluminum housing with a dedicated constant-voltage power supply circuit.
The base is firmly fixed with screws to prevent vibration as well as shielding effect of induction prevention.

An independent tape monitor function with two dedicated tape recorder input / output terminals. In addition, a tape copy switch is provided to enable dubbing between two tape recorders.

It is equipped with a 3-step attenuator that can instantly reduce the volume without changing the volume control.
You can select -20dB, -30dB or ∞ (silence).

Rhodium plated input / output jacks provide excellent durability.

It is equipped with functions such as a compensator that balances energy by raising low and high frequencies that are insufficient at low volume and automatically controls the amount of rise according to the position of volume adjustment, a subsonic filter that cuts out unwanted low-frequency noise outside the audible band, a mode switch that is set to monophonic to check the balance of speakers, a headphone jack for monitoring, etc.

Panel finish with gold-style scratch hairlines with natural Persimmon boards on the side.

Model Rating

Type	Stereo Preamplifier
Frequency Response	Tuner, CD, Line, Tape Play Input : 1.0 Hz to 500 kHz, + 0 -3.0 dB 20 Hz to 20 kHz, + 0 -0.2 dB AD Input: 20 Hz to 20 kHz, + 0 -0.2 dB
Total Harmonic Distortion Factor	0.005% (at all input terminals)
Input Sensitivity / Impedance (Rated Output / EIA Output 0.5 v)	AD : 2.0mV/0.5mV/47k Ω Tuner, CD, Line, Tape Play : 126mV/31.5mV/20k Ω CDBalanced : 126mV/31.5mV/40k Ω (20k Ω / 20k Ω)
Rated Output / Impedance	Output (Balanced) : 2.0V/50 Ω (25 Ω / 25 Ω) (Cannon connector) Output (Unbalanced) : 2.0V/1 ohm (Phono jack) Tape Rec : 126mV/200 Ω (at AD)
Headphones	Applicable Impedance : 4 Ω ~ 100 Ω
S/N / Input Conversion Noise	Input Short, A - Compensation AD:85dB/-140dBV Tuner, CD, Line, Tape Play : 110dB/-128dBV CD Balanced:110dB/-128dBV EIA S/N AD:92dB Tuner, CD, Line, Tape Play : 92 dB CD Balanced:85dB
Maximum power level (0.005% distortion rate, 20 Hz to 20 kHz)	Output(Balanced):10.0V Output(Unbalanced):10.0V Tape Rec : at 19.0V/AD
Maximum Input Voltage (1 kHz, 0.005% distortion)	AD:300mV CD(Balanced):10.0V
Minimum Load Impedance	Output (Balanced) : 600 Ω (300 Ω / 300 Ω) Output (Unbalanced) : 1k Ω Tape Rec : 10k Ω
Gain	Tuner, CD, Line, Tape Play → Output : 24 dB Tuner, CD, Line, Tape Play → Rec Output : 0 db AD → Output : 60 dB AD → Rec Output : 36 dB
Loudness Compensator (volume control -30dB)	1:+3dB(100Hz) 2 : + 8 dB at 100 Hz, + 6 dB at 20 kHz
Subsonic Filter	10 Hz, -18dB/oct
Attenuator	-20dB, -30dB, ∞
Semiconductors used	108 tr, 15 fet, 27 ic, 106 di
Power Supply	100 V, 117 V, 220 V, 240 V, 50/60Hz
Power Consumption	40W
External Dimensions	Width 470x Height (including legs) 145x Depth 373 mm
Weight	15.6kg