NIKKO C-201

Commentary

Professional preamplifier with all-FET configuration.

The equalizer circuit is a first stage low-noise, two stage differential, three stage amplified group source follower circuit. It is two stage amplified with an RIAA element in between.
The C-201 gives an RIAA curve with a CR time constant to avoid the NF type in order to focus on sound quality. This eliminates the phase rotation of the unit amplifier and provides excellent sound quality and fidelity.
The CR type cannot be expected to have a good effect on the S/N ratio and dynamic range. However, the C-201 has achieved an excellent S/N ratio by carefully selecting the components used. For example, a low-noise FET and a metal film resistor with less noise components are used. As for the dynamic range, a high-voltage FET with Vds200V is adopted for the first stage unit amplifier in order to be able to withstand a large input in the high-frequency range.
In addition to improving the S/N ratio by making the final stage high withstand voltage and using a low-noise FET for the first stage differential, we have also studied the bare characteristics and amplified the signal flattened by the RIAA element at a low distortion rate.

The flat amplifier section has a circuit configuration of first stage low noise, two stage differential, three stage amplification, and final stage source follower.
The circuit design emphasizes bare characteristics and achieves FLAT characteristics up to ultra-high frequencies, while utilizing the characteristics of the FET element itself to achieve low distortion.

It uses a 21-point click type 4 connected volume.
Since this volume controls both the input and output of the flat amplifier section, the noise of the equalizer amplifier and flat amplifier is reduced and the S/N ratio in actual use is improved.
In addition, a buffer amplifier section using a source follower circuit by FET is mounted to eliminate the change of output impedance due to the use of four connected volumes and to lower the output impedance, and the dynamic range is expanded by applying a voltage of ± 50 V.

In the power supply section, the power supply for the equalizer amplifier and the power supply for the FLAT AMP are wound separately and supplied as a constant voltage to eliminate interference distortion.
These constant-voltage power supply circuits are composed of error-amplifying transistors and supply a stable constant voltage to each circuit.

The Phono input is provided in the Route 3 so that the load resistance and input capacitance can be changed for CH1, the input capacitance can be changed for CH2, and the load resistance can be changed for CH3. The load resistance can be changed in 5 stages and the input capacitance can be changed in 3 stages, so that the performance of each cartridge can be demonstrated.
In addition, a NAB compensation circuit is provided so that not only disks but also tapes can be played directly from the magnetic head, and a FLAT circuit for MIC is also provided.

The signal system has been simplified by eliminating the tone control circuit, which enables music playback without signal degradation.

Equipped with a protection circuit.
The C-201 is equipped with two pairs of full-scale stabilizing power supplies. Large capacitors are used in various parts of the power supply. It takes time to stabilize the power supply after the power switch is turned on. During this time, irregular noise is generated from the amplifier. To prevent this noise, the output and the amplifier circuit are isolated for 10 seconds after the power switch is turned on. When the power switch is turned off, the output is isolated instantly.
An indicator display circuit also electronically changes the power indicator from red to green to indicate relay operation.

Model Rating

Type	Control amplifier
Input Sensitivity / Impedance	Phono CH1, CH3 : 2mV/22k Ω, 33k Ω, 47k Ω, 68k Ω, 100k Ω Tuner, Aux1, 2 : 100 mv
Input capacity	Phono CH1, CH2 : 0, 47 pF, 100 pF
Frequency characteristic	Phono1, 2 : 20 Hz to 20 kHz ± 0.2 dB Aux and Tuner : 10 Hz to 20 kHz ± 0.1 db
Total harmonic distortion factor	Phono1, 2 : 0.01% or less (at rated output)
S/N ratio (IHF, A-network short circuit)	Phono1, 2 : 72 dB Tuner, Aux, Tape1, 2 : 100 dB
Residual noise	20 μ V
Phono maximum allowable input	400mV
Output Level / Impedance	Output1, 2 : 1V/600 Ω Tape out1, 2 : 100mV/600 Ω
Semiconductor used	FET : 38 Transistor : 21 Diode : 22 pcs
Pwer	100 VAC, 50Hz/60Hz
Power consumption	40W
External dimensions	Width 482x Height 50x Depth 430 mm
Weight	5.8kg