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An annular plenum is integrated downstream of six pulse detonation combustors arranged in a can-annular configuration. The primary purpose of the plenum is the mitigation of flow fluctuations, which is crucial for operation with a downstream turbine. The flow inside the plenum is investigated by means of flush-mounted pressure transducers arranged in axial and circumferential directions. The operability of the system over a range of parameters is demonstrated. The test rig is operated in different firing patterns at frequencies up to 30 Hz per tube. Key parameters such as fill-fraction and firing frequency are varied to characterize the plenum outlet flow conditions. The obtained data allow for a better understanding of wave interaction and attenuation inside the plenum as well as the quantification of pressure fluctuations at the plenum outlet for a wide range of operating conditions. Furthermore, a comparison is made between piezoresistive and piezoelectric pressure transducers showing the capability of piezoresistive transducers for high frequency pressure measurements in a harsh, high-temperature environment.