Samadhi may come just after enlightenment or after nirvikalpa Samadhi when you wake up. That cannot happen in Samadhi because the mind is shut down there. Sri Ramakrishna, in the gospel says that you have to be pure. In Samadhi, what remains? Turiam alone remains. Does Turiam have ignorance? No. It needs knowledge is the waker.
Swami Sarvapriyananda teaches one of the shortest and most profound upanishads accompanied by Gaudapada's Karika. This lecture covers Mantra 7 (Part 2).