Commentary

This stereo control amplifier was developed based on the C-200X and taking over the circuit technology of the advanced C-280.

The circuit configuration of the equalizer and high-level amplifier employs a cascode A-class push-pull system with an FET buffer for direct connection to the input. The next stage is a cascode A-class push-pull and the output is a Darlington A-class push-pull.
The cascode connection is characterized by low feedback between input and output and excellent characteristics, especially at high frequencies, high gain, linearity is maintained up to the operating limit of the element, distortion is reduced and S/N is improved, and excellent characteristics can be obtained. In addition, a Darlington A class push-pull is adopted for the output, and the input impedance can be raised, so that the operation of the preceding stage is hardly affected by the load, and the amplifier can be composed of low distortion factor and wide dynamic range.

The head amplifier for the MC cartridge uses a full-scale method in which a dedicated amplifier is inserted in front of the equalizer amplifier. The circuit configuration consists of three stages : cascode differential push-pull, cascode push-pull, and Darlington push-pull.
Since the signal level of the head amplifier is extremely low, S/N is improved by carefully selecting low-noise elements and designing the circuit with low impedance.

Each unit amplifier is equipped with an IC-based DC servo circuit. This circuit detects the DC component generated at the output and feeds it back to the input in reverse phase to prevent the generation of DC. By this circuit, all unit amplifiers can be directly connected to reduce coloring.

Each unit amplifier is driven by an independent winding and independent rectifier circuit. Each unit amplifier has a built-in dedicated constant voltage power supply to stabilize the unit amplifier and cut off interference between unit amplifiers.

In order to configure the shortest and straight signal path, relays are installed in the signal path where a switch is required, and these relays are controlled electronically by logic circuits for switching.
A sealed audio-only relay is used to improve reliability and long-term durability.

In order to support various MC cartridges, the MC input impedance can be switched in three stages. In addition to the normal head amplifier gain of 26 dB, a gain switching switch is provided for low power MC cartridges to obtain a high gain of 36 dB.

Equipped with 600 Ω balanced output.

The tone control employs a stepping method with an independent 11-contact rotary switch on the left and right sides, and a turnover switch is provided so that only the deep bass and the best range can be changed.
Equipped with an on-off switch to cancel the tone control.

It is equipped with a Loudness Compensator switch that adjusts the sound perception and energy balance during low volume playback.
Two curves can be selected according to the playback level and the characteristics of the listening room. The compensation level is automatically adjusted according to the position of the volume adjustment volume.

3 tape recorders can be connected, and mutual dubbing is also possible.

There was a wood cabinet with natural wood Rosewood finish sold separately.

Model Rating

Type	Stereo Preamplifier
Frequency Response	Tuner, Line, Tape play : 1.0 Hz to 500 kHz + 0 -3.0 dB 20 Hz ~ 20 kHz + 0 -0.2 dB Disc : 20 Hz-20 kHz ± 0.2 dB
Total Harmonic Distortion Factor (EIA)	0.005% (20 Hz to 20 kHz at all input terminals)
Input Sensitivity / Impedance (Rated output / EIA output 0.5 V)	Disc (Head amp off) MM : 2.0mV/0.5mV/47k Ω Disc (Head amp + 26 dB) : 0.1mV/0.025mV/10 Ω, 30 Ω, 100 Ω Disc (Head amp + 32 dB) : 0.05mV/0.0125mV/10 Ω, 30 Ω, 100 Ω Tuner, Line, Tape play : 126mV/31.5mV/20k Ω
Rated Output / Impedance	Output (unbalanced) : 2.0V/1.0 ohm Output (balanced) : 2.0V/600 ohm Tape rec : 126mV/200 Ω (at disc)
S/N / Input conversion noise	Input Short A Correction Input Terminal Rated Input S/N Input Conversion Noise EIA S/N Disc(Head amp off)MM: 85dB -140dBV 82dB Disc(Head amp +26dB): 72dB -152dBV 76dB Disc(Head amp +32dB): 66dB -152dBV 76dB Tuner, Line, Tape play : 110dB -128dBV 88dB
Maximum power level (0.005% distortion rate, 20 Hz to 20 kHz)	Output(unbalanced):8V Output(balanced):8V Tape rec : 19 v (at disc)
Disc Maximum Input Voltage (1 kHz, 0.005% distortion)	Head amp off:300mV Head amp +26dB:15mV Head amp +32dB:7.5mV
Minimum Load Impedance	Output (unbalanced) : 1k Ω Tape rec : 10k Ω
Gain	Tuner, Line, Tape play → Output : 24 dB Tuner, Line, Tape play → Tape rec : 0 dB Disc (Head amp off, MM) → Output : 60 dB Disc (Head amp off, MM) → Tape rec : 36 dB Head amp is switchable between + 26 dB and + 32 dB
Tone Controls	10-step control Bass 500 Hz : ± 7.5 dB (100 Hz), 1.5 dB step 200 Hz : ± 7.5 dB (40 Hz), 1.5 dB steps Treble 2 kHz : ± 7.5 dB (10 kHz), 1.5 dB step 7 kHz : ± 7.5 dB (35 kHz), 1.5 dB steps
Loudness Compensator (Volume -30dB)	Comp1:+3dB(100Hz) Comp2 : + 8 dB (100 Hz), + 6 dB (20 kHz)
Subsonic Filter	10 Hz, -18dB/oct
Attenuator	-20dB
Semiconductors used	Transistors : 164 FET : 16 IC : 21 Diodes : 123
Power Supply Voltage	100 VAC / 117 V / 220 V / 240 V, 50Hz/60Hz
Power Consumption	45W
External Dimensions	Width 445x Height 160 (w / legs) x Depth 373 mm W 466x H 190x D 385 mm (with wood cabinet)
Weight	13.6kg
Sold Separately	Wood Cabinet A-8 (¥ 16,000)