What is the load impedance on the tiny amplifier in a typical MP3 player with five headphones paralleled to it? Is this a good idea?
In general, the resultant load impedance with 5 headphones attached would be very hard on an MP3 player's amp, or most other devices with a 3.5mm headphone out port. However, connecting the 5 outputs of this splitter to the inputs of 5 high-impedance devices (like a receiver's aux audio input) would be no problem for most MP3 players.Most MP3 players can only really handle load impedances down to about 16 ohms, with some maybe being able to take 8 ohms. Most earbuds are around 32 ohms (for example, the Apple earbuds are), and non-professional headphones top out at around 60 - 100 ohms. Some headphones are as low as 16 ohms. So assuming an average impedance of 32 ohms, 5 in parallel would be 6.4 ohms. Although some MP3 players would be able to handle this without burning out, at least at lower volumes, there most likely will be issues, such as high levels of distortion, especially at higher volumes. At higher volumes, there is even the possibility of burning out the MP3 player's amp or triggering some form of over-current protection.However, as I mentioned, connecting a high-impedance device would be just fine. The "line-in" inputs on devices like receivers, PC audio capture cards, TVs, etc, usually have an impedance ranging from around 10k to 100k ohms, so 5 of those in parallel would be no problem at all for an MP3 player's amp.Note that connecting the "line-out" output from a device like a receiver to the input of this splitter, then connecting the 5 outputs of the splitter to 5 other devices, would not work. A receiver's line-out can only handle devices that have very high input impedances (approx 10k to 100k), and in general it's not a good idea to parallel more than about 2 high-impedance inputs to a line-out. Also, low-impedance devices like headphones should never be connected to a "line-out" (only connect them to actual headphone out ports).
Date published: 2012-07-18