Suppose I have a relatively small audio source (Bluetooth earbuds, to be specific), and I have the audio lines hooked up in such a way that under most circumstances, the audio source provides an output voltage without being opposed by anything other than the resistance of a pair of headphones.
However, for convenience purposes, the audio source's output (in both cases where the audio source is playing and not) would occasionally be connected to the output of another (larger) external audio source (like a cell phone or a laptop).
Thus, should I have any concerns about accidentally frying the small audio source with the output from the large one? If so, what would you recommend for an easy way to switch between audio sources (without unplugging anything, preferably)?