Wikipedia
Sadananda (also called Svami Sadananda Das) (1908–1977) was born Ernst-Georg Schulze of Germany. He met Bhakti Hridaya Bon, a disciple of Bhaktisiddhanta Sarasvati Thakura. Bon took Schulze to India, where he received diksa from Bhaktisiddhanta and took the name Sadananda Dasa. He was the first known individual who was not of Asian origin to embrace the Gaudiya Vaishnava tradition. After conversion of Vamana Dasa ( Walter Eidlitz) Sadananda continued to preach in Europe.
Sadananda Yogendra Saraswati, the exponent of the Advaita Vedanta as taught by Adi Shankara and the renowned author of Vedantasara which is one of the best known Prakarana Granthas (text-books) of the philosophy of the Upanishads, was the son of Anantadeva, and probably lived in mid-15th century A.D. He is also reputed to have written - Vedantasiddhanta-sarasangraha, Bhavaprakasa on Bhagavad Gita and Brahmasutra-tatpryaprakasa – which are works of equal repute and importance. Not much is known about the life of this acharya. Hiriyanna states that Sadananda of Vedantasara is different from the Sadananda of Advaitbrahmansiddhi the text that was published by the Asiatic Society of Bengal.
In his works Sadananda stresses the liberated being’s freedom from bondage, detachment from the body, and constant goodness, although being beyond virtue. The liberated being after having lived out his prarabdha karma merges with Brahman.
Adyayananda was the Guru of Sadananda.