There is no one letter to represent this sound, so it is often mispronounced by newcomers to the English language because they tend to focus too much on the written word instead of the sound. When learning new vocabulary in English, always focus more on the sound of the word rather than the way it is written.
I've found that the smallest words present the most problems and are often overlooked. So let's begin with them. Note the various ways the words are spelled but phonetically still have the /ʌ/ sound.
a and uh are both /ʌ/
son and sun are both /sʌn/
one and won are both /wʌn/
country is pronounced /'kʌn-tri/
Please listen to the audio and post your comments or questions below.