A read-channel module includes a variable-gain amplifier (VGA) module, an analog-to-digital converter (ADC) module, an amplitude measuring module, a gain adjusting module, and a zero phase start (ZPS) module. The VGA module has a variable gain, amplifies input signals, and generates amplified signals. The ADC module converts the amplified signals from analog to digital format and generates samples. The amplitude measuring module receives N of the samples and measures amplitudes of the N samples, where N is an integer greater than 1. The gain adjusting module communicates with the amplitude measuring module and selectively adjusts the variable gain of the VGA module based on the amplitudes. The zero phase start (ZPS) module communicates with the amplitude measuring module, receives the samples, and selectively generates phase information from the samples based on the amplitudes.