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This paper presents the development of a high-frequency fine finish power supply in wire-EDM using fixed pulse-width modulation (FPWM) pulse control method. A digital signal processor (DSP) card is employed to generate high-frequency pulse control signals with FPWM for easy modification purpose. The DSP-based power supply can provide very low discharge energy pulses with a frequency of 4.4 MHz, a discharge duration of 90 ns and a peak current of 1.2 A. Experimental results not only validate the applicability of the developed fine finish power supply in reducing the recast layer of titanium and micro-cracking in tungsten carbide, they also demonstrate that the developed system can achieve a fine surface finish as low as 0.16 mum Ra.