Excerpt from: THEORY AND CONSTRUCTION OF MIC "SPLITTERS"
by Bill Whitlock
Read the complete white paper from Jensen.
Red = RF filter network.
Radio frequency filtering is accomplished with a series network consisting of a 0.01uF ceramic capacitor and a 51ohm resistor on every output that shunts frequencies above 300KHz to ground, but looks "open" at audio frequencies.
Green = Secondary winding damping resistor.
If the splitter will not always be used in a fixed configuration, where any of isolated outputs may not be used, it is recommended to install 2.7 kS damping resistors across HI and LO (pins 2 and 3 for XLR's) output pins. If an output is unused, and especially if it has a cable attached which is open at the far end, the unloaded secondary of the "MB" transformer will exhibit an undamped resonance which can adversely affect frequency response of the system.