What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Yamaha C-50

 Uncompromised Circuit and Function Engineering
The C-50 Stereo Control Amplifier features an impressive array of unique circuit innovations that are specifically designed to give you more accurate,, natural music reproduction. In addition to straightforward, sensible circuit design from input to output, the C-50 features a brand new ERE (Extended Rolloff Equalizer) circuit that eliminates the high-frequwncy phase deviation inherent in conventional RIAA equalizer designs, New Linear Transfer circuitry for an absolute miniumu of current distortion caused by semiconductor non-linearity in push-pull class-A amplification stages, and DC configuration circuitry throughout for the highest accuracy in waveform transimssion.
Moreover, each and every individual circuit component has been carefully chosen for optimum characteristics so there is virtually no chance of sound quality degradation due to less than ideal or mismatched components. Functionally, the C-50 provides extensive response tailoring flexibility with continuously variable bass and treble control turnover frequencies. And, like any Yamaha component, all controls give you complete control over the most critical parameters that affect your listening pleasure.
If you'reseriously interested in putting together a truly high-performance separate component audio system, the C-50 is one preamplifier you should definitely hear before makong your final choice - your ears will tell you more than we can ever desribe in words.
 Continuously Variable Tone Control Turnover Frequencies
Tone controls are provided in a preamplifier to allow the listener to roughly compensate for acoustic deficiencies in his listening room, as well as for unbalanced program source response, and, simply to create an overall tonal balance that he finds "pleasant". The control range provided by most tone control systems, however, is severly limited since the bass and treble control turnover frequencies are usually arbitrarily determined  and preset by the manufacturer. Some more advanced tone control systems approach this problem by permitting two or three position switching of the tone control turnover frequencies. The Yamaha C-50 goes even further by permitting continuously variable  control of the bass and treble tone control turnover frequencies over a conveniently wide range. Bass control turnover can be varied continuously from 100 Hz to 500 Hz, and treble control turnover can be varied between 1 kHz and 5 kHz, permiting extensive response control for the most accurate tonal compensation in any listening situation.
 Direct MC Cartridge Input Capability
Today's movening coil phono cartridges offer sound reprodution quality with considerably greater detail and clarity than their moving magnet  counterparts. MC cartridge output level, however, is too low to be fed directly to most phono equalizer amplifiers, requiring an extra stage of amplification in the form of a step-up transformer or pre-premplifier.
Simply setting the C-50 phono selector  to "MC" permits direct input of MC cartridges without the need for a separate step-up device. Phono input sensitivity and impedance characteristics are automatically switched for optimum performance with high-quqlity MC cartridges such as the Yamaha MC-1X/1S, MC-3, MC-5, MC-7 or MC-9
 New Linear Transfer Circuit
Although push-pull class-A-bias amplification stages offer overall reproduction accuracy  greater than class B configurations, conventional versions of this circuit suffer from current distortion due to the fact that the "gm" (mutual transconductance) curve of any semiconductor is distinctively non-linear outside its ideal flattest portion.
Signals falling outside the transistors flattest gm range become distorted.
Yamaha engineers found a way to minimize this type of distortion in the New Linear Transfer circuit. This advanced circuit adjusts the bias to the class-A stage semiconductors according to the size of the input audio signal, thereby ensuring that the semiconductors linear gm range always corresponds to the audio signal being processed. This means that an absolute minimum of current distortion is assured with any input signal.
In the C-50 all amplification stages from the phono equalizer to the output stage feature the Yamaha new Linear Transfer system.
 Selectable MM Cartridge Load Capacitance
A fact about moving magnet phono cartridges that is given too little attention in modern audio preamplifiers is that thier high-end frequency response can very considerably depending on the capacitive load presented to the cartridge by the preamplifier's  phono inputs. This means that the user must specifically choose a cartridge that matches his amplifier's input capacitance in order to achieve the best possible reproduction quality. The C-50 eliminates this performance limitation by providing switchable 100pF, 220 pF or 330  pF load capacitances (all at 47 k Ω) that will provide optimum matching with just about any moving magnet cartridge available. The C_50 phono load selector also features a 100 Ω position for use with hig-input moving-coil cartridges.
 ERE (Extended Rolloff Equalizer)
With the vast improvements in overall amplifier performance, the time has come to provide an RIAA  equalizer capable of equally fine performance. Today's low-level flat-response amplifiers easily achieve virtually distortion free  response up to 100 kHz or more. Conventional RIAA equalizer amplifiers, however come nowhere near this outstanding performance. The Yamaha ERE meets the modern performance standards by eliminating phase variation beyond the range where conventional equalizers begin to deviate from the RIAA curve. This type of extended equalizer accuracy was previously impossible to achieve because of high-frequency instability limitations. The Yamaha ERE completely eliminates this instability while providing an accurately extended high frequency curve, permitting greater reproduction precision than has ever been possible.
The Yamaha ERE ciruit makes a difference in phono reproduction that you can hear. And it's a difference you'll really appreciate because you'll discover nuances and subtleties in the music on your favorite records that you may never have heard before.
 Rec Out Selector
This unique Yamaha feature permits simultaneous monitoring and recording of two different sources. For example, you can set the Rec Out selector to Phono  and the Input selector to Tuner, then settle back to listen to your favorite radio program while simultaneously taping a friend's record.

4-Gang Volume Control
In most preamplifiers, gignal-to-noise ratio deteriorates as volume is reduced because the amplifier's residual noise level becomes proportionately larger in relation to the audio signal as audio signal level is reduced. Yamaha's four-gang volume control however reduces the amplifir's residual noise as well  as the audio signal level, thereby maintaining an extremely high signal-to-noise ratio all the way down to the lowest of low listening levels. No matter how low you set the volume, musical detail will not be obscured by unwanted noise.

Disc Direct Function
This advanced feature reflects yamaha dadication to giving you nothing but the most natural sound reproduction quality available. When the Disc Direct function is engaged, the many input selector switch contacts as well as the entire tone control system are completely bypassed, coupling the output of the ERE phono equalizer amplifier directly to one of the C-50's high-performance flat amplifiers. This provides the purest most straightforward signal path achieving the ultimate in disc reproduction accuracy.

Solenoid/Relay Function Switching
The C-50 features a unique light-touch function switching matrix that adds considerably to overall operating ease and convenience.  This system has been made possible by the incorporation of a solenoid switching system for input selection (this helps to minimize signal lead lenght in the input stage thereby maximizing sound quality) and relay switching for the Disc Direct and Audio Muting functions. The relays used feature special gold-clad contacts which ensure that absolutely no sound degradation occurs due to contact resistance.

Other Features
Dual AUX terminals.
Flip-down control cover.
Switchable 15 Hz subsonic filter.
Phono 1 / 2 selector
Stereo / Mono mode selector.
Optional EIA rack mount adaptors.
Input Sensitivity/Impedance: 
Phono MC : 100µV/100 Ω
Phono MM : 2,5 mV/100 Ω
100 / 220 / 330 pF : 2,5 mV/47 k Ω
Aux, Tape, Tuner : 150 mV/47 k Ω
Input Sensitivity (New IHF):
Phono MC : 33µV
Phono MM : 0,83 mV
Aux, Tape, Tuner : 50 mV
Maximum Input level (1kHz, 0,01% THD/New IHF)
Phono MC : 8.5 mV/8 mV
Phono MM : 220 mV/220 mV
Output Level/Impedance:
Rec Out : 150 mV/470 Ω
Pre Out : 1,5 V/47 Ω
Maximum Output level (20 -20,000 Hz, 0,1% THD)
Pre Out : 10 V
Headphone Maximum Output level/Impedance (1 kHz,0,01% THD, Output Impedance 68 Ω):
0,45 V /8 Ω
4,0 V /100 Ω
Frequency Response  (Aux, Tape, Tuner to Sp Out):  DC to 100,000 Hz +0 -0,5 dB
RIAA Deviation:
Phono Mc : 20 to 20,000 Hz ±0,2 dB
Phono MM : 10 to 100,000 Hz ±0,5 dB
Total Harmonic Distortion:
Phono MC to Rec Out 3 V output : 0,002%
Phono MM to Rec Out 3V output : 0,001%
Aux, Tape, Tuner to pre Out 5V output (Tone switch Off) : 0,001%
Intermodulation Distortion (Aux, Tape, Tuner 5V output. Tone Switch Off):  0,002%
Signal-to-Noise ratio (IHF-A Network/New IHF)
Phono MC (500 V, Input Shorted) : 90 dB / 80 dB
Phono MM (500 V, Input Shorted) : 93 dB / 81 dB
Aux, Tape, Tuner (Tone switch Off) : 105 dB / 96 dB
Residual Noise (IHF-A Network):  2,8µV
Channel Separation
Phono MM/Aux, Tape (5,1 k Ω, Input Shorted)
40 Hz, 1 kHz, 10 kHz : 85 dB/85 dB;  80 dB/70 dB;  68 dB/53 dB
Subsonic Filter Characteristics:  15 Hz , -12 dB/oct
Audio Muting:  -20 dB
Tone Control:
Bass (boost/cut):  ±10 dB
Treble (boost/cut):  ± 10 dB
Turnover Frequency:
Bass : 100 to 500 Hz
Treble : 1 to 5 kHz
Power Supply:  110 -120 V, 220 - 240 V AC 50/60 Hz
Power Consumption:  40 W
Dimensions (W x H x D):  435 x 96,5 x 369 mm (17-1/8" x 3.¾" x 14-½")

Weight:  6,6 kg (15 lbs)

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