There have been occasions where providing power for a Tuner Genius XL (TGXL) using a 13.8 VDC power supply has resulted in voltage sags, resulting in anomalous operation with the TGXL. Operating the TGXL using a 13.8 VDC power supply that is also supplying DC power to other devices may not be sufficient.
The TGXL has a minimum working input voltage of 15 volts. It can operate on voltages up to 25 VDC. Operating the TGXL below the minimum voltage threshold is not recommended.
Several TGXL owners have been using 18VDC @ 2A switching power supplies with good results. Here is an example of a power supply available from Amazon that is compatible with the TGXL's coaxial power connector: https://www.amazon.com/Adapter-Compatible-Brookstone-Bluetooth-Speakers/dp/B0BLRPQ3YQ/ref=sr_1_7
Note: Any third-party products mentioned in this article have not been endorsed by FlexRadio or 4O3A.