dc-type voltage reset characteristics for amorphous ribbon, permalloy ribbon, sendust ribbon, and amorphous fiber were examined and compared with constant current reset characteristics (CMC) up to 500 kHz. A new instrument with square-wave driving is developed. We defined the control force by using the average value of control current when the control current flows forwardly with control voltage. An amorphous core with ribbon thickness of 5 μm exhibited highest gain among the cores. This clarified that the average value of reset magnetizing force for an amorphous core corresponds to the average speed of flux reset and that dc-type voltage reset characteristics for an amorphous ribbon are almost identical to CMC at high frequencies. These results are applicable for a detailed steady-state analysis of magnetic amplifiers.