We introduce a new class of quasi-hereditary algebras, containing in
particular the Auslander-Dlab-Ringel (ADR) algebras. We show that this new
class of algebras is preserved under Ringel duality, which determines in
particular explicitly the Ringel dual of any ADR algebra. As a special case of
our theory, it follows that, under very restrictive conditions, an ADR algebra
is Ringel dual to another one. The latter provides an alternative proof for a
recent result of Conde and Erdmann, and places it in a more general setting
