Chirped-pulse amplification in a Yb 3+-doped phosphate glass regenerative amplifier pumped by a free-running Ti:sapphire laser is demonstrated. Amplified chirped pulse energies up to 20 mJ were obtained. Amplified bandwidths of 20 nm at reduced energies were obtained using regenerative spectral shaping. Spectroscopic measurements are presented which are necessary to model amplification in a quasi-three-level laser.