The operating voltage on the PMTs is -2,950 V. This is a near maximum rated voltage and it has been shown to combine high efficiency, good P/V ratio, and long PMT life. The overall gain of the PMT is not maximum, as is measured by BURLE, since the dynode chain of the 13 dynodes (2nd dynode to 14th dynode) is kept at -2,600 V equivalent with the original 300 resistor value between Cathode and 1st dynode. However, the gain is more than sufficient to separate the one PE from the pedestal of all ADCs we have used so far. It should not be necessary to increase the voltage above the recommended one.