Is /æ/ sound always same?
There are multiple ways of pronouncing this phoneme. The “pure” pronunciation is a near-open front unrounded vowel [æ] (as in cap and back), which as you can see on a vowel chart is directly between [ɛ] (Э) and [a] (А).
Before a nasal consonant such as /n/, it is also pronounced as [eə] or [εə] (as in can and Mary) in many accents.
Furthermore, in English, unstressed consonants are usually pronounced [ə], so “can” is often pronounced [kən] as in “I can do that”.