Description
As an improved version of the C-2, this control amplifier uses newly developed parts including a low-noise High-gm Dual FET. The basic circuit configuration is a low-noise head amplifier for MC cartridges, a low-noise equalizer amplifier assembled with a current noise reduction circuit, and a high-precision tone control amplifier. All amplifier circuits are balanced full-stage push-pull, which in principle suppresses distortion, and is also DC-configured. The main improvements from the C-2 to the C-2a are improved characteristics and added functions. First of all, all characteristics such as distortion rate, S/N ratio, frequency characteristics, and transient characteristics have been greatly improved. Then, a Phono Selector and Rec out Selector have been added, and a continuously variable tone control has been adopted. In addition, parts that have been carefully selected for their sound quality are used throughout. The first stage of the equalizer amplifier section uses a newly developed low-noise High-gm Dual FET (2SK101). The 2SK101 has excellent low-noise characteristics, especially low 1/f noise, and has a high gm of 120mho (Typ.), and is an Nch silicon junction FET with matching electrical and temperature pair characteristics of paired FETs.The circuit configuration is a differential circuit with low-noise, high-gm dual FETs, and a new cascode bootstrap circuit that is effective in improving DC drift, which is a problem with DC amplifiers, preventing deterioration of distortion due to increased signal source impedance when cartridges are installed, improving frequency characteristics, and reducing current noise, and is also equipped with an auto-balanced active load that is effective in reducing distortion. The predrive stage of the equalizer amplifier section is composed of a current mirror differential push-pull circuit. In addition, the output stage is a two-stage emitter follower complementary push-pull circuit with transistors that have high fT and sufficient collector loss.The current mirror circuit reduces distortion, and the two-stage emitter follower complementary push-pull circuit achieves a low output impedance of 100? while providing sufficient output voltage with low distortion. The RIAA element that determines the accuracy of the equalizer uses high-precision, large-capacity metal film resistors and newly developed high-precision polypropylene film temperature-compensated capacitors, achieving high accuracy. A current noise reduction circuit is installed to reduce current noise generated by the load resistance of the cartridge.In this circuit, the load resistance is set to a large value to reduce current noise. In addition, to prevent the characteristics from being adversely affected by increasing the load resistance, a resistor several times higher is used, and the desired load resistance is obtained by the current noise reduction circuit.As a result, the load resistance becomes a fraction of the resistor used, which reduces the current density of the input-equivalent noise, and an equivalent load resistance with less noise is obtained. The MC head amplifier section is a DC amplifier configuration with a new cascode complementary push-pull circuit in which four NPN/PNP low-noise transistors with low rbb (base resistance) and large hfe are connected in parallel to reduce voltage noise, and one more is connected in cascode. The low-noise transistors are connected in parallel to form a complementary push-pull circuit, achieving excellent low noise and low distortion characteristics. The Phono1 circuit of the C-2a can set the load resistance and load capacity to suit the cartridge used. The load resistance can be switched between three levels by the Phono Selector, and the load capacity can be set by connecting a capacitor to the Cartridge Load terminal on the rear panel. The 100? position is a position exclusively for high-output MC type cartridges. The circuit design of the tone control amplifier is almost the same as that of the equalizer amplifier, and is a NF type tone control circuit with a mid-point defeat.The first stage uses a one-chip dual FET with excellent thermal balance, and furthermore, by assembling a cascode bootstrap circuit, the drift of the midpoint voltage, which is important in DC amplifiers, is suppressed to a minimum. In addition, a volume is inserted in the front stage of the tone amplifier, but by adopting a cascode bootstrap circuit, the deterioration of the distortion rate due to the fluctuation of the signal source impedance when the volume is operated is suppressed.The pre-driver stage is a differential cascode current mirror output with low impedance drive by an emitter follower, preventing the deterioration of the loop frequency characteristic due to the mirror effect of the feedback capacitance of the element.The output stage uses a pure complementary OCL circuit with transistors with well-matched complementary characteristics with a high high-frequency limit frequency (fT), and the output impedance is sufficiently low. The tone amplifier is designed so that the element with a time constant is completely removed from the signal path at the midpoint of the tone control volume, and it operates as a wideband flat buffer amplifier.In addition, it is a DC tone control circuit in which no capacitors other than the polypropylene film capacitor for setting the frequency characteristic are inserted even when the tone control is used. The time constant element for tone control uses the same polypropylene film capacitor (1% accuracy, 50PPM/? temperature characteristic) and metal film resistor as the RIAA element, and the control volume uses a newly developed conductive plastic volume with a high accuracy and special curve. Equipped with a subsonic filter. The power supply circuit uses an OI core transformer that is small but has very good regulation and low leakage flux, and an electrolytic capacitor from the audio low noise series with low distortion. In addition, a cascode bootstrap active load is assembled to a low drift comparison amplifier using dual transistors, and a low noise avalanche effect diode is used for the diode for generating the reference voltage, forming a low distortion, low noise, high speed response constant voltage power supply circuit. In addition, the power supply for the MC head amplifier, which is easily affected by power supply fluctuations, is further reduced in impedance by a local power supply. The C-2a uses high-quality parts such as a low-impedance 70? thick printed circuit board + pure copper bus earth, IO core transformer, Yamaha original audio coupling capacitor, high-precision conductive plastic volume, new mechanism rotary switch, and other metal film resistors and polypropylene film capacitors. In addition, gold-plated cut-type pin jacks and connectors are used to improve reliability. Equipped with a -20dB audio muting circuit. Equipped with a Rec out Selector, you can select the signal to Rec out regardless of the program source that the amplifier is playing. Rec out and Pre out1/2 are equipped with relay circuits to prevent shock noise when the power is turned on and off. Equipped with AC outlet Type Control amplifier amplifierInput sensitivity/impedance Phono1 MM: 2.5mV/47k?, 68k?, 100k?Phono1 MC: 100?V/50?Phono2 MM: 2.5mV/47k?Aux, Tuner, Tape PB1/2: 150mV/47k?Cartridge load 100k?, 68k?, 47k?, 100?Maximum allowable input Phono1 MC: 10mV or more (20kHz, 0.03%)Phono1/2 MM: 350mV or more (1kHz, 0.01%)Aux, Tuner, Tape PB1/2: 30V or more (Volume -34dB)Rated output/impedance/maximum output Pre out1/2: 2V/250?/15V or moreRec out1/2: 150mV/100?/20V or moreFrequency characteristics Phono1/2 MM: 20Hz to 20kHz 0±0.2dB (RIAA)Phono1 MC: 20Hz to 20kHz 0±0.3dB (RIAA)Aux, Tuner, Tape PB1/2: 10Hz to 100kHz +0 -0.2dBTotal harmonic distortion (20Hz to 20kHz) Phono1/2 MM: 0.003% or lessPhono1 MC: 0.01% or lessAux, Tuner, Tape PB1/2: 0.003% or lessHarmonic distortion (20Hz to 20kHzSum of 2nd to 10th orders at HP-IB) Phono MM?Rec out(1.5V): 0.0007% or lessAux, Tuner, Tape1/2?Pre out: 0.0007% or lessIntermodulation distortion Aux, Tuner, Tape PB1/2: 0.003% or less (10V output)Signal-to-noise ratio (IHF-A network) Phono1/2 MM: 92dB or morePhono1 MC: 78dB or moreAux, Tuner, Tape PB1/2: 103dB or moreResidual noise 0.03?V or lessChannel separation(1kHz, Volume max) Phono1/2 MM: 90dB or morePhono1 MC: 78dB or moreAux, Tuner, Tape PB1/2: 90dB or moreFunction separation(1kHz, Volume max) Phono1/2 MM?Tuner: 90dB or moreTuner?Phono1/2 MM: 95dB or moreAux?Tuner: 90dB or moreTone control characteristicsTurnover frequency Bass: 350HzTreble: 3.5kHzMaximum variable range Bass: ±10dB (20Hz)Treble: ±10dB (50kHz)Subsonic filter 15Hz, 12dB/octAudio muting -20dBSemiconductors used FET: 5 piecesSemiconductor: 101 piecesZener diode: 10 piecesDiode: 32 piecesAC outlet switched: 400Wmaxunswitched: 400WmaxPower supply AC100V, 50Hz/60HzPower consumption 36WExternal dimensions Width 435 x Height 72 x Depth 320mmWeight 7.9kg
Live search