Systems and designs for tuning a wireless power transfer system are provided, which may include any number of features. In one embodiment, a wireless power transfer system can be configured such that resonant frequencies of the system move towards an operating frequency of the system as a coupling coefficient between the transmit and receive resonators becomes smaller. In another embodiment, a receive controller can be configured to control a current delivered to a DC load by comparing an actual current at the DC load to a current requested by the DC load and adjusting an angle or a magnitude of a voltage at the DC load to match the requested current. In another embodiment, a rectifier circuit can act as a controlled voltage source and be configured to tune resonant frequencies between the transmit resonator and the receive resonator. Methods of use are also provided.