A study has been performed to evaluate the effectiveness of a closed-loop control system to suppress thermo-acoustic combustion instabilities. The pulse-width modulation technique was implemented both in a numerical simulation of a dynamic combustion instability and experimentally. The control system was effective in suppressing a simulated thermo-acoustic oscillation based on a simplified system model. The control system is undergoing scale-up design and will be tested on a 200 kW gas turbine combustor rig. The experimental apparatus is described in detail below along with its baseline operating characteristics. The combustor exhibits a strong thermo-acoustic combustion instability which manifests itself in large pressure and flame emission fluctuation amplitudes near a frequency of 140 Hz. The instability tends to grow as the fuel and air flowrates are increased from those corresponding to the lean stability limit. Open-loop control experiments using main fuel flow modulation indicate that the combustion process can be manipulated to produce strong pressure fluctuations at the driving frequency. Closed-loop control experiments using pulse-width modulation on the main fuel injector are currently underway and will be reported in a future paper.