I've started using some in-ear monitors, and I'm not sure if they are high resistance or low resistance, but they are very sensitive to volume. The lowest volume setting on my phone is plenty of volume, and three notches is the most that I ever need, I have turned on the volume limiter on my phone but it's still goes up to like 7 out of 10 which is way too much. If the volume is ever inadvertently pressed and held down, it could blow out my ears and the idea of that freaks me out. As far as I can find, there aren't any further options in my phone that would solve the problem, all I get is that limiter which is way too much. It works well for normal headphones and IEMs but not something as sensitive as these are.
With headphone amps as I know that they generally work, the best I can think of is to 3D print a cover that would go around the volume knob so that it cannot be altered unless the cover is removed, but surely there must be something with a built-in locking mechanism like a switch or some such thing that will do this easier than having to create a cover to physically prevent the knob from being able to be turned unless I mean to do it.
If I can lock it in place, then I could turn the volume all the way up on my phone, and then set the amp to the loudest that I would ever want to listen to it, and then permanently lock the volume in place and never touch it again, and then that would be my volume limiter. I could do all of my actual volume adjustment with the phone