کلیه حقوق متعلق به وبلاگ برق - فیزیک می باشد و کپی برداری از مطالب در وبلاگ ها و وب سایت های دیگر فقط با ذکر منبع مجاز می باشد .
مدیر وبلاگ : حامد ص
Volume and Loudness controls CD and Aux inputs
P1______________47K Log. Potentiometer (twin concentric-spindle dual gang for stereo) R1,R2,R4_______100K 1/4W Resistors R3,R14_________560R 1/4W Resistors R5_______________1K 1/4W Resistor R6,R7,R10_______10K 1/4W Resistors R8,R9___________22K 1/4W Resistors R11_____________68K 1/4W Resistor R12______________1K5 1/4W Resistor R13_____________12K 1/4W Resistor C1_______________1µF 63V Polyester Capacitor C2,C3__________100pF 63V Polystyrene or Ceramic Capacitors C4______________47nF 63V Polyester Capacitor C5______________22nF 63V Polyester Capacitor C6_____________220pF 63V Polystyrene or Ceramic Capacitor C7,C10_________100nF 63V Polyester Capacitors C8,C11___________4µ7 25V Electrolytic Capacitors C9,C12________2200µF 25V Electrolytic Capacitors IC1___________TL072 Dual BIFET Op-Amp IC2___________78L15 15V 100mA Positive Regulator IC IC3___________79L15 15V 100mA Negative Regulator IC D1,D2________1N4002 200V 1A Diodes SW1____________DPDT Toggle Switch SW2____________2 poles 3 ways Rotary Switch J1,J2,J3,J5____RCA audio input sockets J4_____________Mini DC Power Socket
This is the first article of a five-part series describing a complete
audio preamplifier formed by five Mini-Modules, namely: Control Center,
Switching Center, Phono Preamplifier, Tone Control and Headphone
Amplifier. A suitable Power Amplifier module is already available here: 45 Watt Class B Amplifier.
The modular arrangement allows the amateur to choose only the modules
more suited to his requirements in order to build a chain one to five
Each module, excepting the Switching Center that is a passive
circuit, incorporates its own separate power supply rectifiers and
regulators and requires only an external 15 - 18V ac (50mA minimum)
Power Supply Adaptor.
Each electronic board can be fitted in a standard enclosure: Hammond extruded aluminum cases are well suited to host the boards of this preamp. In particular, the cases sized 16 x 10.3 x 5.3 cm or 22 x 10.3 x 5.3 cm are the more appropriate and can be stacked with advantage.
Control Center circuit description:
This circuit features two high-level inputs switched by SW1, followed by the unity-gain high input impedance buffer IC1A. The output of this buffer drives the passive network Loudness circuit. Its control switch SW2A allows the choice of two different frequency compensation curves (see graph below) to be used when the sound programme is reproduced at low levels. Curve I should be used with low to mid reproduction levels, in practice when the volume control knob is set around the second quarter of its travel. Curve II is best suited to very low levels, i.e. when the volume control knob is set around the first quarter. To obtain a perfectly flat frequency response, the Loudness control must be set in the OFF position.
The following Op-Amp (IC1B) provides all the gain required by the preamplifier, featuring 166mV RMS input sensitivity at 1.5V RMS output with very low distortion. Therefore it is capable of driving low input sensitivity power amplifiers.
The dual rail power supply necessary for this circuit is drawn from the single 15 - 18V ac voltage provided by a suitable external Power Supply Adaptor. D1 and D2 rectify respectively the positive and the negative half wave in order to obtain a dual opposite polarity rail voltage referred to ground. IC2 and IC3 provide a well regulated ±15V dc supply to the Op-Amps.
Loudness Frequency Response:
A possible arrangement of the front and rear panels of this Module
Having Questions? comment me
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دوشنبه 5 تیر 1396 08:06 ب.ظ
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