Up to 650kHz high repetition active Q-switching was achieved with a pulse-width of < 40ns by using a diode-side-pumped Nd: GdxY1-xVO4 bounce amplifier. An average output power of 17.5W was obtained at a pump power of 41W. The pulse repetition frequency range of the stable Q-switching operation was adjusted without any loss of the average output power by changing the Gd:Y mixture ratio. (c) 2006 Optical Society of America