I have a small DC motor being driven by a controller which supplies +6V/-6V to the motor to control its speed and direction (elliptical machine resistance control motor). The issue is that 6Vs is not provide enough speed/power from the motor, but if I drive the motor with a 9V or 12V battery it works sufficiently. The controller determines the position of the mechanism with a potentiometer and changes the driving voltage accordingly until the correct position is reached. What I would like to do is double the voltage being supplied to the motor (to +12V/-12V), while leaving the rest of the system intact. I have been trying to research simple cheap boost converters, but I cannot figure out if these devices can take a varying +/- input voltage and output the corresponding +/- voltage with double the amplitude. Thanks in advance for any insight anyone can provide.