This paper presents a first mathematical model for estimating the output spectrum spurs of dual-path hybrid (DPH) DC-DC converters and proposes a ?S-modulation control technique to reduce harmonic spikes. The proposed model is hand-calculation friendly and can ensure reasonable accuracy. It features the prediction of the output spectrum spurs that can compromise the noise characteristic of the converters. We also propose a spur reduction method using a 2-2 MASH ?S-modulator to replace the conventional pulse-width modulation control, realizing a 4th order noise shaping function for better noise and limit-cycle spike suppression with relaxed stability issue. Simulation results show that the ?S-modulation controlled DPH converter achieves a spectrum spike reduction of 17. 6dB and 15.2 dB in low-and high-frequency conditions, respectively, compared with PWM control.