Next letter is Ъ ъ [Ǎ ǎ]
The English equivalent is ‘u’ as in ’t[u]rn’
Let’s list some Bulgarian words starting with the letter [Ъ];

Ъгъл [Ǎgǎl ] -> (an) angle {m.}

!! NB

This letter is a hard sound. In Bulgarian, this is the only word that starts with Ъ. If anything, any other word with such a letter in the beginning - it would be a foreign name (e.g. Ърнест [Ernest]). The letter is normally within words - never staring and never ending a word in modern Bulgarian. In the past, it was written as ѫ [yus]. In daily speech, that hard sound sometimes is rounded and it may sound as an А (like in “b[a]t”). This, of course, sometimes hinders the correct spelling of some words because people often mix the sound of it with the proper grammar. So, be wary and pay attention to words with that letter.