volume control and dissipated power

[makanaky]

hi all ,

does increasing volume control of cassette or mp3 player consumes more power from the battery ?

i will tell u what i think and tell me if it's right or wrong :

i think not because my imagination of volume control is a potentiometer with fixed current and when changing the volume control , the voltage is take from different points along the potentiometer , so P=I²*Rtotal = constant

so is that right ?

 

[nguyennam]

Power dissipated by the volume potentiometer is constant, but the power (voltage more exactly) required by the input stage of the amplifier increases when you increase volume, however, as usually, this power is very small and negligible. So the power dissipated by the volume potentiometer is unchanged.

But remember that when increasing volume, the power supplied to the amplifier increases.

nguyennam

 

[cydi]

these days noboody is using a potentiometer based volume control. The controls are all digital. Basically, its the variable gain of the output stage that is digitally controlled. Some times its the attenuation, which is changed digitally.... These inputs are from one of my friends who is into CE products...

 

[jinal patel]

just power supplied to the amplifier increases but now a days all controls are digitized. so in terms of cost you may think that it increases slightly

 

[rkodaira]

First: the potentiometer volume control acts over output amplifier gain or over the output amplifier input signal. But the power supplied by the amplifier to the headphones or loudspeakers will change with the volume level, which uses more or less power from the power supply.

Another variable is the output amplifier class used in the device. Class A amplifiers use power even when they are idle (no signal), with signal in the input, the output voltage will vary around Vcc/2, but changing a little about average consumption.
Class B uses very small power when there is no input signal and with signal, they start to consume power from the supply.