Power amplifier electronic circuits-tube audio rf amplifiers

Electronic Amplifier Circuits-Power amplifier, audio amplifier designs and circuits

August 20th, 2009

Speaker To Michrophone Converter

About The Circuit
This is the simplest way of converting a loud speaker to a michrophone. Though the output voice is not so conventional, an average quality output will be obtained for sure. The circuit has to be assembled neatly in a PCB.
The basic working is that when the sound waves hit the diaphragm of the speaker, the coils in the diaphragm will fluctuate, causing a small considerable amount of induced voltage. Voltage gain is obtained by connecting the transistor Q1 in the common base mode. Current gain is obtained by connecting the transistor Q2 as an emitter follower. The circuit requires an input voltage from a 9 V PP3 battery. The capacitors must have a minimum rating of 15 Volts. The speaker K1 should have 3 inch thickness. Inorder to collect the produced sound in the output an 8 Ohm speaker or headphone is more than necessary.
It must be noted that while setting the circuit, keep the preset R2 at around 10 Ohms and connect the battery. Later adjust R2 until you get good sound quality.

 

Circuit Schematic

speaker to michrophone converter circuit

August 20th, 2009

Simple Graphic Equalizer Circuit

About The Circuit

Given below is the circuit diagram of a simple three band graphic equalizer circuit. An IC called LF 351 IC is used here which is designed to operate as a wide bandwidth single operational amplifier. The IC also has a very high input impedancewhich helps the circuit to become more compatible to almost all the audio signal sources.

An input voltage between (6-30) Volts can be applicable to this circuit. It is to be noted that as the inpt voltage increases the gain will also increase. If an input voltage of 12 Volts is given for the circuit the electrolytic capacitors used in the circuit should be more than 12 Volts. The op-amp used in the circuit is wired as an inverting amplifier. The input signal is first passed on to the inverting input through the filter network. This filter network can produce a +20 to -20 dB enhancement or a cut on the frequency bands, 50Hz,1KHz and 10KHz.The gain of the se banda are adjusted using the POTs R1, R2 and R3. The circuit should be assembled on a PCB.

Circuit Schematic

simple-graphic-equalizer-circuit.jpg

August 20th, 2009

Simple Sub-Woofer Amplifier

About The Circuit
Given below is a 100 Watts sub-woofer amplifier that has been designed only with the use of transistors. There are mainly seven transistors, in which two of them are used in the pre-amplifier stage and four of them in the output stage.
The greatest advantage of this type of a circuit is that there are no IC’s used and so is easy to assemble on a PCB. This circuit is designed to produce 100 Watts output and an input power of +35V/-35V, 5A dual supply is to be used. The size of the sub-woofer depends on the outpu and a normal specification of 12 inch is required. It must be noted that the transistors Q4, Q5, Q6 and Q7 are fitted along with heat sinks. The electrolytic capacitors used here should have a rating of 100 Volts.

Circuit Schematic

100-w-subwoofer-amplifier-circuit.jpg