Voltage gain Vs Power Gain

You can use the amp for headphone or earbud. I designed it for my earbud. I buy them at dollar tree for a $1 each. They have headphones too, I like the ear bud better. Any way I ran the sim for both so you can see how that works.

With my earbud I get 175mv-pk.

With the headphone I get over 400 mv-pk. So which is better? The one you have of course. Oh well if you have a choice which would perform better with this amp?

Wow 75 uw should drive the headphone well. Actually 1 or 2 uw will drive a sound powered phone well.

But look at the ear bud. Close to 500 uw. Yes the ear bud will produce as much sound as the headphone. The earbuds are rated 90dbm - 110dbm and the phone is rated up to 120dbm. The phone is a little more sensitive but the amp will drive the earbud harder with a smaller input.
I have been using this amp to drive a single earbud. The plug was bad on the bud so I split the cord and made 2 singles. The little amp drives the single bud very well.