We propose a calculation for the amplification coefficient γ q of acoustical phonons interacting with electrons in a quasi-one-dimensional GaAs channel subjected to an external dc electric field. Two regimes of temperatures have been investigated and it has been found, by considering only intrasubband transitions, that the amplification coefficient for a particular frequency, and for phonons propagating along the channel length ( z -axis), is a step-like function of the applied field at low temperatures. For high temperatures the amplification coefficient shows an exponential behavior as a function of the applied electric field. Furthermore, provided the one-dimensional quantum channel has high electron mobility values, coherent acoustic-phonons can be amplified in modest electric fields.