Why is my mp3 player running out of battery power?

October 24, 2007 6:45 PM

Why does my MP3 player run out of battery power so rapidly when I connect it to an amplifier and speakers as versus when it is connected to my headphones?

I have a small 1gig mp3 player whose only power source is a single AA battery. When I connect it to any amplifier (at the same volume) to output through speakers I feel like I can watch the battery drain... why would the power used have anything to do with what it is connected to?

posted by geos to technology (4 comments total)

Battery Life and Radio Volume. Somewhat old link but it should explain it.
posted by Memo at 6:51 PM on October 24, 2007

why would the power used have anything to do with what it is connected to?

If you re-phrase it to "Why would power used have anything to do with power outputted?" you'll be on the right track. The amplifier produces a far greater power to produce a listenable level of sound for speakers compared to headphones and so consumes a far greater amount of power. There are a few reasons, proximity to your ears being the obvious and most significant. But the speakers are almost certainly a lower impedance than the headphones (you can measure this if you have a multimeter) so at any given volume setting will consume more power.
posted by 6550 at 7:04 PM on October 24, 2007

The amplifier produces a far greater power to produce a listenable level of sound for speakers compared to headphones and so consumes a far greater amount of power.

But the amplifier has it's own AC power, perhaps I should have mentioned that in the question. I am connecting it to a stereo amplifer(s) plugged into the wall.
posted by geos at 7:13 PM on October 24, 2007

It is pretty strange, because the input impedance of the amplifier should be substantially higher than the headphones, thus requiring much less power. Perhaps the high input impedance leads to parasitic high frequency oscillations in the output stage - seems unlikely, but I can't think of anything that seems likely, so..

There are a lot of things you can do to analyze it in more detail, mostly involving temperature probes and oscilloscopes..
posted by Chuckles at 8:26 PM on October 24, 2007