When you turn down or up the volume on devices with either a wheel or button, what actually happens that allows it to sound quieter or louder?
In: Technology
Nowadays the wheel or buttons generate pulses that control a computer that controls the D/A converter that controls the volume of the signal. To get increased dynamics, there can be one D/A converter for the volume and one (much more high resolution) for the signal, multiplied to get the end result, but it’s not a given. Also, the equalizer is completely digital, using digital (calculated) filters.
A system consists of some signal source (tape player, radio etc), usually a preamp, an amplifier and a speaker.
The volume control sits between the preamp and the amplifier. The preamp produces a signal that is (generally) about 1 volt. The volume control has a long resistor, with a wiper that makes contact with the resistor at some point along its length. The preamp output is connected to one end of the resistor, and the other end is attached to the 0 volts point (‘ground’). The wiper is connected to the input of the main amp, which produces a signal with the voltage and power needed to drive the speaker.
When the volume is high, the wiper attaches to the resistor right beside the input. So the full 1volt signal appears at the input of the main amp. When the volume is fully down, it the wiper attaches to the resistor right down at the ground point – there’s no voltage there, as it is at 0 volts, so the main amp sees no signal and you get nothing out.
Anywhere between that, the wiper contacts the resistor somewhere along it’s length, and so the main amp sees somewhere between the full 1v signal and nothing, controlling the volume.
A volume knob or wheel is an example of a device called a *potentiometer*, which is a device that adjusts the voltage going down a wire by increasing or decreasing the electrical resistance.
If the resistance increases (if you turn the volume knob down), then less voltage makes it to the speaker, the cone vibrates less intensely, and the sound is quieter. The opposite is true if you turn the volume up.
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