Attenuating Headphone Cable
My headphones are too loud. I have in-ear headphones which seal out outside noise and are quite sensitive. I have to keep the volume at its lowest setting, almost off, for comfortable listening. This has two drawbacks: it is painfully loud if the volume ends up at its max setting, and there's usually a hiss coming from my phone or laptop which competes with the music at the lowest volume setting.
To fix this, I made a short headphone cable which reduces the volume. This is similar to the headphones which have a volume knob or slider built into the cable, except that it only has one setting: quiet. The circuit is two simple voltage dividers, one for the left channel and one for the right channel. I found the resistor values through trial-and-error on a breadboard, just trying different values until I found some that gave the ideal volume reduction. The circuit is tiny enough to fit inside the headphone jack and it works well. I can now comfortably use the entire volume range when listening to music, and at the higher volume settings the hiss is drowned out by the music so I can't hear it any longer.