Headphone amplifiers with RCA input

RCA

— RCA is technically a type of connector that can be used for a variety of purposes. However, in this case, a very specific application is implied — in the format of a line input (for an analogue audio signal). In this format, one physical connector is responsible for one channel of sound, so this type of input usually consists of a pair of jacks — for the left and right channels.

In general, linear RCA is practically not used in portable devices, but it is very popular in stationary audio equipment. It is somewhat inferior to more advanced standards (like XLR, see the relevant paragraph) in terms of functionality and noise immunity, but this interface is often quite enough for both everyday and simple professional use.