Sound activated switch using LM386
• Build an Amplifier: Audio amplifiers are everywhere. There are some in concert halls as well as in Hi-Fi systems as well as Bluetooth speakers. We owe them the pleasure of the bass which makes the body tremble but also that of the treble sounds so pleasant to listen to... Do you know how an amp works? What are the components that transform an insignificant signal into a powerful electric current capable of powering large loudspeakers? This complete video explains on the one hand what are the characteristics of an amp and what are the different types of speakers. You will then discover the precise operation in class A, B and even D amplifiers. This information will allow you to understand the logic of electronics and to manufacture your own amplifiers!
Excerpts:
By the way, how does a loudspeaker work? It is like an electric motor that works back and forth. They consist of a coil connected to a membrane and a magnet. When an electric current flows through the coil it becomes more or less magnetic and is sometimes attracted to the magnet, sometimes repelled. Ideally the movement of the coil and therefore that of the membrane reproduce identically the variations of the signal. As it moves through the air, the membrane creates more or less strong pressure waves, in other words sound. Loudspeakers are everywhere, there are speakers, phones, computers, headsets, earphones, and many other devices of all sizes.
A loudspeaker alone is inefficient, it has trouble communicating all its power to the air and then there is an acoustic short circuit. To put it simply, the waves they produce in front or behind are opposite and cancel each other out. To remedy this, you can install a baffle, that is to say a plate that separates the two sides to isolate them. In this case the sound power is much higher but the baffle must be very large, it is not really practical! Fortunately, there are different speaker technologies that make it possible to limit the size. The simplest is the closed enclosure. The inner wave is trapped so we only hear the outer wave. The most widespread technology is the bass-reflex enclosure which has a vent. The sound comes out of the vent with a slight delay which makes it possible to add the previous wave with the new one coming out of the loudspeaker, a way of increasing the sound power without consuming more energy.
Coming back to amplifiers, they can easily be characterized by two parameters. The first is gain. An amplifier that has a gain of 10 multiplies the amplitude of the input signal by 10. It is given more or less 2V in input, it outputs more or less 20V. So obviously all this is true as long as the output amplitude does not exceed a maximum value. If you give a 3V signal to this amplifier and it is supplied with 20V, it obviously cannot output 30V to you. The output signal will be clipped high and low and it does something like this... it's called saturation. The second parameter that characterizes an amp is its internal resistance, also called output impedance. The lower it is, the more the amp will be able to deliver a high output current. All without significant voltage drop or overheating.
So how does a Class D amp work? To understand what makes it so special, you have to see why Class A and B amps perform so badly. If we try to make an alternating voltage, a bit like music, from a direct voltage, we realize that a good part of the energy must be lost in heat. This heat appears in transistors that are never fully turned on or turned off. It would therefore be necessary to find a system in which the transistors operate only in all or nothing, like a switch.
Sound activated switch using LM386
• Build an Amplifier: Audio amplifiers are everywhere. There are some in concert halls as well as in Hi-Fi systems as well as Bluetooth speakers. We owe them the pleasure of the bass which makes the body tremble but also that of the treble sounds so pleasant to listen to... Do you know how an amp works? What are the components that transform an insignificant signal into a powerful electric current capable of powering large loudspeakers? This complete video explains on the one hand what are the characteristics of an amp and what are the different types of speakers. You will then discover the precise operation in class A, B and even D amplifiers. This information will allow you to understand the logic of electronics and to manufacture your own amplifiers!
Excerpts:
By the way, how does a loudspeaker work? It is like an electric motor that works back and forth. They consist of a coil connected to a membrane and a magnet. When an electric current flows through the coil it becomes more or less magnetic and is sometimes attracted to the magnet, sometimes repelled. Ideally the movement of the coil and therefore that of the membrane reproduce identically the variations of the signal. As it moves through the air, the membrane creates more or less strong pressure waves, in other words sound. Loudspeakers are everywhere, there are speakers, phones, computers, headsets, earphones, and many other devices of all sizes.
A loudspeaker alone is inefficient, it has trouble communicating all its power to the air and then there is an acoustic short circuit. To put it simply, the waves they produce in front or behind are opposite and cancel each other out. To remedy this, you can install a baffle, that is to say a plate that separates the two sides to isolate them. In this case the sound power is much higher but the baffle must be very large, it is not really practical! Fortunately, there are different speaker technologies that make it possible to limit the size. The simplest is the closed enclosure. The inner wave is trapped so we only hear the outer wave. The most widespread technology is the bass-reflex enclosure which has a vent. The sound comes out of the vent with a slight delay which makes it possible to add the previous wave with the new one coming out of the loudspeaker, a way of increasing the sound power without consuming more energy.
Coming back to amplifiers, they can easily be characterized by two parameters. The first is gain. An amplifier that has a gain of 10 multiplies the amplitude of the input signal by 10. It is given more or less 2V in input, it outputs more or less 20V. So obviously all this is true as long as the output amplitude does not exceed a maximum value. If you give a 3V signal to this amplifier and it is supplied with 20V, it obviously cannot output 30V to you. The output signal will be clipped high and low and it does something like this... it's called saturation. The second parameter that characterizes an amp is its internal resistance, also called output impedance. The lower it is, the more the amp will be able to deliver a high output current. All without significant voltage drop or overheating.
So how does a Class D amp work? To understand what makes it so special, you have to see why Class A and B amps perform so badly. If we try to make an alternating voltage, a bit like music, from a direct voltage, we realize that a good part of the energy must be lost in heat. This heat appears in transistors that are never fully turned on or turned off. It would therefore be necessary to find a system in which the transistors operate only in all or nothing, like a switch.
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