Power amplifier electronic circuits-tube audio rf amplifiers

About The Circuit

A 2 transistor tone controller circuit is illustrated below. This simple circuit is made with the help of Baxndal tone control design. A 12 Volt DC power os required for the circuit. Also note that the connection for the input and output is given in respect to the ground. Two POT’s are used. Out of these POT R5 is to bring adjustments to the bass and POT R8 is to bring adjustments to the treble. Sufficient current gain and input impedance must be provided by the circuit. For this reason, the transistor Q1 is placed as an emitter follower. Voltage amplification of the signal is provided by the second transistor. Tone is controlled by the resistor and capacitor network connected between emitter of Q1 and base of Q2. Variation of the values of these resistors and capacitors change the audio response of the system. On the frequency ranges of 10KHz to 60Hz, a maximum attenuation and boost of 10decibel is obtained. All electrolytic capacitors should have a rating of atleast 12 Volts.

Circuit Schematic

About The Circuit

A circuit diagram of a simple stereo line driver circuit is given below. BC 109c transistors are used for driving each channel by wiring them as emitter followers. Apart from the transistors, only a few passive components are wired. The emitter followers are very ideal for driving long cables. They have a voltage gain of and also a high current gain and low output impedance, which makes tem ideal for driving loud speakers.

The circuit should be made on a PCB with a 12 Volt power from a battery or a DC power supply. It must also be noted that the line driver circuit is placed near  to the audio source. At the listening end, a power amplifier is required as the emitter follower has only unity voltage gain.

Circuit Schematic

About The Circut

Here is the circuit diagram of a 741 IC based 3 input mic mixer ckt. Altogether four 741 IC’s are used out of which IC1, IC2, and IC3 are used as pre-amplifiers. A 40 dB gain is produced by the op-amp on the induvidual input circuits. A summing amplfier (IC4) is also used so as to add the signals from the three pre-amplifiers. A 5 dB gain is provided by IC 4 to the final output signal. So totally 45 dB’s is produced as the gain.

The circuit should be assembled on a high quality PCB. It must be noted that the inputs and outputs are connected with respect to the ground. The power should be given from a +15/-15 V DC dual power supply. All the IC’s must be mounted on holders for their safety. Only 10 Volt rating is required for the electrolytic capacitors C1, C2, and C3, while the other capacitors must have a rating of 30 Volts. Take a look at the circuit schematic.
Circuit Schematic