Difference between /ʌ/ and /ə/ in English IPA

If someone who is a linguistics expert could explain this to me in a way I can understand, I'd really appreciate it. I get that /ʌ/ is used on stressed vowels and /ə/ on reduced vowels, but they sound exactly the same to me.

'Strut' (/strʌt/) is given as an example word for the former, and 'comma' (/ˈkɒmə/) for the latter, but I pronounce both of those words the same. I'm confused as to how these differ from a sound perspective.

"I get that /ʌ/ is used on stressed vowels and /ə/ on reduced vowels."

No. Yes, "/ʌ/ is used on stressed vowels", but there is no phoneme /ə/ in English. There is only an allophone [ə] of various unstressed vowel phonemes, including /ʌ/. (I am giving you my own idiosyncratic opinion here -- some linguists will disagree.) You're not going to be able to deal with the difference you're concerned about until you have some idea of the difference between phonemes and allophones.

Phonemes are perceptual, while allophones are actually pronounced. Unless they have some training in phonetics, or are just naturally very good at phonetics, English speakers don't hear schwa at all, because there is no such phoneme. They will hear a schwa as some similar vowel phoneme, probably caret /ʌ/. But there is nothing intrinsically impossible about hearing and pronouncing both sounds, it is just being stuck with the English phonological pattern that makes for the difficulty.

You have to get beyond the usual limitations of English speakers in order to control both schwa and caret. I suggest taking careful note of your tongue position as you say various unstressed vowels. I find that my tongue is retracted toward the back of my mouth when I say caret, but not retracted when I say schwa.

If there is only one central vowel in a language, then for speakers of that language, the difference between /ə/ and /ʌ/ will be very difficult to hear.

Both of these vowels are articulated with the same portion of the tongue (what we call the "centre") being higher—in other words closer to the roof of the mouth—than the rest. The difference between them is that /ʌ/ is more open. In other words the jaw is slightly lower and the gap between the tongue and the roof of the mouth is slightly greater.

The difference in quality between STRUT and schwa, therefore, is akin to the difference between /e/ and /æ/, the vowels in DRESS and TRAP. The vowel in TRAP requires the jaw to be slightly lower than the for the vowel in DRESS.