Clipping is one of the main problems that causes distortion in amplifiers. It causes the amplitude level of a waveform to drop suddenly before it reaches the limit that it was supposed to reach. Well, here is a simple circuit that will help to detect the clipping in a waveform. The clipping can be identified as an LED is kept as the alert indicator when a clipping occours.

This circuit will show correct accuracy if you are able to make it on a high quality PCB. The circuit is mainly based on the working of two operational amplifers (TL 082) inside IC1. They act as window comparators. All it does is to detect the input signal and find out its positive or negative peak value. Correct calibration of the circuit can be done with the POT R5, while POT R1 has to be adjusted to the level at which the LED is supposed to glow.

As we can see Diodes D1 and D2 are connected to the output of the operational amplifier. They are used to drive the transistor Q1 which further drives the LED to glow. A very small time delay is induced by the capacitor C5 so as to identify rapid as well as short peaks. The circuit will easily work with the help of a 9 Volt battery. The circuit is very useful and can be used on all types of power amplifiers, pre-amplifiers and mixers.

Circuit Schematic

Here isthe circuit diagram of a simple power megaphone circuit. All you have to look out for is whether you get the perfect power and speaker matching. For that the transistors Q1 and Q2 (HEP 230) are connected in parallel. An input voltage supply of 12 Volts is required. It can be either given from a battery supply or a DC power supply. A carbon type michrophone is more than enough for the circuit to work. It is the same component that is used in our ordinary telephone sets. A Push-to-talk (PTT) switch can be easily setup if we use an ordinary carbon type michrophone.

Any type of power transisitors can be used for this circuit. You have to only look out that the transistors used are kept on heat sinks. The volume control can be adjusted wiith the help of the POT R1, through which you will get max. volume with min. distortion. Take a look at the circuit diagram given below.

Circuit Description

The circuit has to be made neatly in a printed circuit board. We must also note down that the capacitors have a minimum rating of 15 Volts. The IC uA 741 should be mounted on an IC base. For adjusting the volume level POT R6 can be used.

Circuit Schematic

Though the headphones that are present in the market today are good enough, the music player may not be able to provide enough power to drive the headphone. The only way to make them produce a clear and gud sound is to amplify them. For this, a very simple circuit is enough consisting of three amplifiers. The circuit only needs a 3 Volts battery and needs to be made on a good quality Printed Circuit Board.
The transistors used for this circuit are BC 239 BC 337 and BC 327. Out of these Q1 (BC 239) acts as the pre-amplifier, while transistors Q2 (BC 337) and Q3 (BC 327) act as the driver circuit for the speaker. The performance of the circuit is increased by feeding back the emitter voltage of Q1 the base of Q1 itself through the resistance R3. You must also note down that the capacitors have a rating of 10 Volts. After the circuit is made all you have to do is ON/OFF the switch S1.

Circuit Schematic

Here is a simple guitar pre-amplifier circuit. The circuit is designed for high oimpedance type electric guitar pickups. An op-amp IC uA 741 is all that is required. uA 741 IC is IC1 which acts as the non-inverting amplifier. The volume can be controlled with the help of POT R1 and the tone can be controlled with the help of POT R6. The tone effects can be adjusted to “SOFT” and “BRILLIANT” modes with the help of switch S1.

An input voltage of 12 Volt DC power supply or battery is more than enough, though a maximum of 24 Volts can be used.

Circuit Schematic

Here is the circuit diagram of an audio monitoring system which can be easily setup on a PCB. The main use of such a circuit is to transmit a sound from one location and to reproduce it on the other end with the help of a reciever. In this ciruit both the power supply as well as the signal that is transmitted share the same wire.

As seen in the figure, it must be noted that the terminal A is connected tp A’using the wire of required length. The same procedure must be followed for B to B’. A simple speaker of 8 Ohm and 2 Watts is required as K1. The gain of the transmitter circuit is controlled by the POT R2. while POT R14 is used to control the gain at the reciever end. A 12 Volt battery or 12 Volt DC power supply is enough as the input voltage.

The microphone M1 picks up the audio signals. The signals will then be amplified by the double stage amplifier build along with the transistors Q1 and Q2. The microphone has no special specifications. It can be a general purpose one. The by[pass of all the audio frequencies and noise from the line is done by the capacitor C4. C4 also ensures the pure DC for the circuit. The audio signal output of the amplifier is coupled to the line with the help of the capacitor C6. The audio signal from the line is extracted and is fed to the inverting input of TL 071, which is the IC1 in the circuit. This operation is done by the capacitor C7. The integrated power amplifier IC2 for which an LM 386 IC is used recieves the output of IC1. IC2 also provides all the necessary current gain to drive the speaker. The audio frequencies are isolated along with the noise from the power supply of both the IC’s with the help of capacitor C1.

Circuit Schematic

Given below is an IR audio link circuit that has been designed to transmit audio signals as far as 4 meters. The signal is passed on to the base of transistor Q1 through the resistor R4. This signal, when passing the transistor Q1 makes the transmitting diodes D1 and D2 ON.
The circuit has to be neatly designed on a PCB with a 9V PP3 battery for powering the transmitter and reciever. The IR signals that are transmitted are modullated along with the audio input.

The IR signals that are transmitted will be recieved by the photo transistor Q2. On recieving it the emitter voltage of the photo transistor changes according to the strength of the IR signal, which again depends on the sound modullated. Apart from Q2, there are also ordinary transistors Q3 and Q4 which are used to amplify the signal to drive the speaker. Capacitor C1 and Resistor R3 are connected as a filter circuit so as to avoid the interference from all the stray IR signals.

A simple 8 Ohm speaker is enough for the output. The photo transistor Q2 should be an NPN type. They can be anyone like PNZ154, PNA1605F, BPW77NA or BPW85.

Circuit Schematic

Circuit Schematic

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

Circuit Schematic