3.5 mm Analog Line Input
A 3.5 mm analogue line-input count states how many mini-jack sockets receive a stereo line-level signal.
The input receives audio from a source. It does not drive headphones, even though the connector can look the same as a headphone-output socket.
3.5 mm Analog Line Input — Headphone Amp
On a headphone amplifier, this input can accept an appropriate analogue signal from a portable source, DAC or other line-level output. The amplifier then controls and amplifies that signal for its headphone output.
Compare the source’s output function and level with the amplifier’s input requirements. One stereo input socket is not two separate inputs. A headphone output used as a source may require appropriate level adjustment; a digital USB connection is a different signal path and should not be included in this analogue input count.