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I'm surprised no one has discussed battery life yet. One of my 'weird unverified theories of life' is that turning the volume on portable device down (laptop/p

I'm surprised no one has discussed battery life yet. One of my 'weird unverified theories of life' is that turning the volume on portable device down (laptop/phone/mp3 player) and the volume on the speakers up saves the battery of the device itself. (For example when you're in a car.)

nagrom 14y ago
From the link, it appears that to get 'lower' volume, you scale the output values if digital, whereas you may scale the output signal if analogue. If you have an analogue output (stereo jack), then you probably generate a lower-power output and therefore save energy by turning the volume down. If you use digital out, then the volume of your local device doesn't have any bearing on the battery life of that device, because you are effectively putting out numbers. But I could be wrong!
mbell 14y ago
A small amount, perhaps. In all likelihood your probably better off setting the volume on the device somewhere in the middle, but this will vary based on device. Two major things come into play: 1) The input impedance of powered speakers or any external processing stage will be high. ~5-10k ohms, compared to 80-500 ohms for an average set of headphones. This means regardless of the level you use on the player the current draw will be substantially lower than it would be if driving headphones. This means the level doesn't matter nearly as much. 2) The efficiency curve of the output amplifier. Depending on the topology of the output amplifier of the device it may be more or less efficient at different power levels. If the output driver is a class AB topology it actually gets more efficient as it nears its rated output (generally the relationship is logarithmic). As a result you can actually be 'better' overall on power to using a higher power level at some points in the curve. You use more power to drive the output but you also increase efficiency reducing your overall power usage. Class AB is pretty in-efficient anyway as your only going to see 30-50% peak efficiency. With a class D output which is becoming more popular you can see upwards of 90% but your efficiency vs output power curve is generally sharper, you get much closer to peak efficiency much faster (depending on the exact design of course, most portable devices will be filter-less class D topologies).

nagrom 14y ago

From the link, it appears that to get 'lower' volume, you scale the output values if digital, whereas you may scale the output signal if analogue. If you have an analogue output (stereo jack), then you probably generate a lower-power output and therefore save energy by turning the volume down. If you use digital out, then the volume of your local device doesn't have any bearing on the battery life of that device, because you are effectively putting out numbers. But I could be wrong!

mbell 14y ago

A small amount, perhaps. In all likelihood your probably better off setting the volume on the device somewhere in the middle, but this will vary based on device. Two major things come into play: 1) The input impedance of powered speakers or any external processing stage will be high. ~5-10k ohms, compared to 80-500 ohms for an average set of headphones. This means regardless of the level you use on the player the current draw will be substantially lower than it would be if driving headphones. This means the level doesn't matter nearly as much. 2) The efficiency curve of the output amplifier. Depending on the topology of the output amplifier of the device it may be more or less efficient at different power levels. If the output driver is a class AB topology it actually gets more efficient as it nears its rated output (generally the relationship is logarithmic). As a result you can actually be 'better' overall on power to using a higher power level at some points in the curve. You use more power to drive the output but you also increase efficiency reducing your overall power usage. Class AB is pretty in-efficient anyway as your only going to see 30-50% peak efficiency. With a class D output which is becoming more popular you can see upwards of 90% but your efficiency vs output power curve is generally sharper, you get much closer to peak efficiency much faster (depending on the exact design of course, most portable devices will be filter-less class D topologies).