Complex sentence: Like the T-34, the DB design had a rear drive sprocket and a forward situated turret, but unlike the T-34, the DB design had the preferred three-man turret crew: commander, gunner, and loader.
Split into simpler sentences: Like the T-34, the DB design had a rear drive sprocket. Unlike the T-34, the DB design had a three-man turret crew: commander, gunner, and loader.