IPA is so detailed that it can represent two schwa-like sounds in English. The upside-down "e" when the syllable is unstressed, and a upside-down "v" for the clearer sound when it is.

Compare "but"(stressed) and the final syllable of "system" (unstressed). In a word like "rubber," the final vowel is so indistinct that a third symbol is often used: a dot under the "r" (when the "r" is pronounced.

It takes practice to hear some of these distinctions, but eventually you wonder how you could ever have thought the sounds were identical.