In this paper we present the low-noise electronics for a prototype of rubidium maser based on the coherent population trapping (CPT) phenomenon. After an overview of the general architecture, we will focus our description on the main blocks of the equipment we implemented: the microwave synthesis chain, the detection apparatus, the clock servo system and the electronics devoted to control the laser and the temperature. For each part, we present the design, the implementation, and the characterization measurements we performed. The contribution to the CPT maser frequency stability of each part also has been evaluated, and the frequency stability of the clock is reported.