Japanese speakers
Mistake: Pronouncing it as "KOORU ASU" with a light Japanese l and a full [a] onset for "us".
Why: Katakana English has no dark l and preserves each word as separate.
Fix: The dark l [ɫ] of "call" links directly to the [ʌ] of "us": [ˈkɔːˈlʌs]. Say "callus" as one word — it sounds like the noun "callus" (the skin condition).
Korean speakers
Mistake: Producing light Korean ㄹ and glottal reset before "us".
Why: Korean prosody adds glottal onsets and Korean l is lighter than English dark l.
Fix: English l in "call" is dark [ɫ] — tongue tip at alveolar ridge, back of tongue raised. Link to [ʌ]: [ˈkɔːˈlʌs], smooth flow, no gap.
Spanish speakers
Mistake: Producing a light Spanish l, or extending the vowel of "call" too long.
Why: Spanish l is light; Spanish vowels can be longer than English equivalents.
Fix: English dark l [ɫ] followed by [ʌ]: [ˈkɔːˈlʌs]. Same as saying "callus" (skin condition) or "careless" without the ess-ending's.