YAMAHA C-50

Commentary

A control amplifier equipped with a pure current dam and a new linear transfer, inheriting the design concept of the high-grade C-70.

The circuit of C-50 is a pure A-class system with a new linear transfer of DC configuration. It is also composed of a unit amplifier equipped with a pure current dam which is an advanced type of pure current servo.

In each unit amplifier except for 6 db amplifier, tone control amplifier and headphone amplifier, pure current dam which is an advanced type of pure current servo is adopted.
In this circuit, a semiconductor inductance in series with the power supply and a high-capacity electrolytic capacitor cut off the power supply with the non-linear component flowing in the power supply line at several Hz so that only the DC component flows. Thus, each unit amplifier is cut off from the power supply when AC is low, and at the same time, the change of the current in the ground line is suppressed.
In principle, this pure current dam operates without the need for a bypass current, making it an efficient and excellent power supply system.

Unit amplifiers, excluding buffer amplifiers and headphone amplifiers, are equipped with new linear transfer circuits.
This circuit works so that the voltage drop across the emitter resistor between the two elements is always constant, and the power supply supplies the same distortion-free current as the output signal. This eliminates the effect of current distortion caused by the gm curve of the element, which cannot be avoided with conventional pure class A bias circuits.

Real-time equalizer developed in C-70 is used in the equalizer section.
This circuit uses two RIAA elements and uses an NF-CR type configuration to achieve ideal equalization in terms of frequency and time. This equalizer also has excellent RIAA deviation, combined with the use of the original low-noise FET to achieve stable clear reproduction.

In the MC head amplifier, an original low-noise transistor with excellent audibility is used in complimentary service, and an excellent SN ratio is obtained.

The newly developed logic control is used for the input selector. This method uses a newly designed plunger switch to improve the operability of the selector operation.
A highly reliable gold-clad relay is used in the disk direct and muting switches. These two switches have a built-in memory that can be restored to the previous state of use at the next power ON.

Equipped with a disk direct switch.
This switch allows you to pass the Input Selector, Mode Selector and Tone Control and simply output the output from the equalizer amplifier to the Pre out.

The tone control section is a continuously variable turnover frequency system.

It uses high-quality parts such as electrolytic capacitors in plastic cases, high-precision RIAA elements, non-magnetic gold plated pin jacks, and oxygen-free copper power cords with polarity.

Yamaha's original high-precision 4-series volume is used.
This is done by attenuating before and after the flat amplifier. The resistance value of the volume can be made smaller than that of the normal one, and SN failure in actual use is improved.

Equipped with a Direct Phono MC terminal that is directly connected from the input terminal to the MC head amplifier.

Model Rating

Type	Control amplifier
Input Sensitivity / Impedance	Phono MC : 100 μ V/100 Ω Phono MM : 2.5mV/100 Ω, 47k Ω / 100 pF, 220 pF, 330 pF) Aux, Tape, Tuner : 150mV/47k Ω
Maximum Allowable Input (1 kHz)	Phono MC:8.5mV Phono MM:220mV
Output Voltage / Impedance	Rec out : 150mV/470 Ω Pre-out : 1.5V/47 Ω
Maximum power output	Pre out : 10 v (20 Hz to 20 kHz, 0.01%)
Headphone Output / Impedance	4.5 V (100 Ω), 0.5 V (8 Ω) / 68 Ω (1 kHz, THD0.01%)
Frequency characteristic	Aux, Tape, Tuner : DC ~ 100 khz + 0 -0.5 db
RIAA deviation (MM, MC)	20 Hz to 20 kHz ± 0.2 dB 10 Hz to 100 kHz ± 0.5 dB
Total harmonic distortion rate (20 Hz to 20 kHz)	Phono MC-Rec out:0.002%(3V) Phono MM-Rec out:0.001%(3V) Aux, Tape, Tuner (Tone off) : 0.001% (5 v)
Cross modulation distortion factor	Aux, Tape, Tuner (Tone off) : 0.002% (5 v)
Signal-to-noise ratio	IHF-A-Network (Input Short) Phono MC : 76 dB (100 μ V) Phono MM:87dB(2.5mV) Aux, Tape, Tuner (Tone off) : 105 dB New IHF Phono MC:80dB Phono MM:81dB Aux, Tape, Tuner : 96 dB
Input Equivalent Noise (IHF-A-Network)	Phono MC:-156dBV Phono MM:-139dBV
Residual Noise (IHF-A-Network)	2.5 μ V
Channel separation (1 kHz, Vol. -30dB)	Phono MM : 70 dB (short) Phono MC : 75 dB (short) Aux, Tape, Tuner : 70 dB (5.1k Ω)
Tone control	Bass : Turnover frequency : 100 Hz to 500 Hz Maximum variation : + / - 10 dB Treble : Turnover frequency : 1 kHz to 5 kHz Maximum variation : + / - 10 dB
Filter characteristic	Subsonic Filter : 15 Hz, -12dB/oct.
Audio Muting	-20dB
Tracking error	2dB
Semiconductor used	Transistor : 116 units IC : 9 FET : 8 LED : 9 pcs Diode : 80 pcs
AC outlet	Switched : 1 system, 500 Wmax Unswitched : 2 lines, 500 Wmax total
Pwer	100 VAC, 50Hz/60Hz
Power consumption	40W
External dimensions	Width 435x Height 96.5x Depth 369 mm
Weight	6.8kg