Total posts : 45366
I use the wall wart supply which was supplied with the AMT3000. It doesn’t have a brand name on it but it is marked 18 VAC, 500 mA.
I had a bit of hum at first and found it was due to having the “GAIN” control set too high. The hum was coming from an audio ground loop and not the power supply. Does your unit hum with the audio cables unplugged? If it doesn’t then this is not a power supply problem, rather it is a ground loop problem. Radio Shack sells a ground isolator which should solve the problem.
There are three jumpers on the transmitter board which can be set to isolate the unit at RF from the audio ground and the power leads. You might try removing these and check if that decreases the hum.
There was a long thread about hum problems on this board some time ago. If I can find it I’ll edit a link into this thread. You might try the SEARCH function on the left side of the screen.