Abstract
In this paper we present a broadly tunable high-power THz FEL amplifier driven by a photoinjector with a seed source tunable between 0.7-2.0 THz. A fully synchronized THz seed pulse is provided by an optical parametric amplifier pumped by the very driver laser of the electron injector. The FEL amplification gain is almost 3000 at 2 THz for nominal input beam parameters.