There was a topic started 'over there' by wdcx about the Talking House power supply, but I thought it was apropos enough to continue over here (considering that Mighty1650 asked a question which has yet to be answered).
The Talking House power supply is prone to hum, as it is grounded to the electrical outlet to which it is plugged in. Computers and other electrically noisy devices, if they are on the same circuit, are usually the cause. John asked if it could be because the device (and power supply) is rated at 18 volts. I have tried running the TH on 12 volts, and it does work (how well in terms of range, I never measured); I also noted no increase or decrease in hum.
To eliminate the hum generated by noise, you can usually experiment and try plugging in the wall wart to other outlets on different circuits, but sometimes an entire room (i.e., your studio, with all its devices) is covered by a single circuit.
You CAN ground the Talking House by other means. Someone 'over there' states, it would then not be 'complaint', which is NOT necessarily true. You would be potentially voiding the certification, but really, all the certification means is that the transmitter can be sold in the U.S. You as the operator are still responsible for ensuring that it is 'complaint' (compliant) with Part 15.
Probably the best way to do that would be to run a short ground wire from the chassis to a good ground - the antenna + feedline (none if you are using the wire antenna) + ground wire has to be at most 3 meters in length (regardless of what that length was when the Talking House was certified - the antenna + the length of the ground wire in the power lead is probably greater than 3 meters even in its certified state, and heaven forbid if you plug in an extension cord or power bar).
Hum can also be generated in the audio feed, so I always use a ground isolator. And if you do ground the transmitter by the chassis, you can use a better quality power supply that is better filtered. You can also thread torroids over the power lead (no matter what you use), and it does make a difference.