I have some good Sennheiser on-ear earphones with a small male plug but it has two red lines around it.

4.4mm balanced adapter cable and is it Is there a 3.5mm to 4.4mm balanced adapter cable and is it

Similarly, if you hook up a stereo plug to a mono output jack, you will likely only hear sound from the left audio channel.

But the headphone jack would think (I know they don’t actually think, but) it’s designed, rather, to send the stereo signal out to headphones, and only a mono signal in.

4.4mm Balanced Audio Cable 8 Core In-Ear UGREEN MMCX to 4.4mm Balanced Audio Cable 8 Core In-Ear

The Cayin iHA-6 headphone amplifier featuring low and high impedance ¼” single-ended, dual 3-pin XLR balanced and 4-pin XLR balanced headphone outputs from Cayin . it could be wired as a normal headphone splitter totally ignoring the mic input or it could do what you need it to do.Royal Mail First Class International Tracked Airmail - Items are usually delivered within 10-15 working days. Please do not ask how it changes the sound, balanced output only helps you get more power from a DAC/AMP that supports it.