Don’t know if this is relevant (from Gollihur Music website):
Important Compatibility Note for Preamps, Pickups, and "Active" Instruments that use a "TRS" or "Stereo" Output Jack
Active circuits generally use a TRS (aka stereo) output jack to switch the circuitry on and off when a regular mono cable is inserted into the jack. The solid "sleeve" of a standard mono plug bridges the contacts to complete the circuit and turn on the electronics (and unplugging turns it off so it doesn't drain your batteries.) The special design of this wireless system uses a TRS plug, too - to allow for its easy charging in the dock. However, this means that it will NOT bridge the contact on an active preamp or an instrument with active pickups (like a bass guitar or an NS Design CR model bass.) Since it won't "turn the circuit on," the instrument won't make sound.
The solution is simple - using a small, lightweight adapter between the wireless and the instrument/preamp output will provide the correct contacts to make everything work, and it's easy and inexpensive. We provide an add-on option, so that you can include one with your purchase of this wireless system if you need it, so you don't have to go searching online to find one.