Most headphones designed for mobile use will hover around 16Ω or 32Ω, which is very easy for your smartphone to handle. The higher that number is, the more it resists current, and the quieter it can get with the same output. Search for the “impedance” spec and take note of the number followed by the Ω symbol. So how can you tell if you need an amp? Click on over to the specifications pages of the products you’re looking at. Though most new headphones will never have this issue because they’re designed to work more efficiently with smartphones, planar magnetic and other high-current cans will still need an amp of some sort. If you’re absolutely sure your headphones aren’t broken, you may need an amp for your headphones. Most headphones nowadays are a lot more power efficient, so this is a very rare problem. But it’s something you should know how to rule out if something’s amiss.

Using an amplifier like this one can properly run power-hungry headphones.