Selective electrical stimulation using a multielectrode array is a promising technique that can potentially bring electrical stimulation treatment modalities a step forward. A microcontroller-controlled electrical stimulator system delivering a single pulse was designed, suitable for current-field modulation. The goal is to make electrical stimulation with surface electrodes more specific. A graphical user interface (GUI) was developed to control stimulation parameters and current-field within a multi-electrode array wirelessly. The stimulator generates arbitrary biphasic waveforms with a 5-bit resolution and high temporal precision (<10 μs) and was demonstrated to stimulate posterior lumbar root fibers in transcutaneous spinal cord stimulation (tSCS) treatment selectively. Current-field modulation throughout a sixteen-electrode array was achieved. The system has the goal to improve control of stimulation conditions in electrophysiological studies and time-dependent and site-specific stimulation patterns for neuromodulation applications. A novel feature is the current-field modulation ability of the stimulator for surface electrode arrays.