Torroidal transformers (round, like a donut) are infamous for humming when they don't get clean power. This is usually caused by dimmer switches. Plugging into a different outlet might not help since all of the outlets in your house/apartment are eventually tied together back at the breaker box. The light in my microwave has a dimmer on it and causes my power conditioner in the basement to hum even though they are on different breakers. I also have a lamp with a dimmer that causes the same problem. If you are in an apartment, the problem could be a dimmer in another apartment. Good luck.
Help Preamp Hum
I am an owner of a Golden Theater GTX 1 preamp/processor. I have owned this unit for approximately a year and have really enjoyed it. Recently, I noticed an annoying buzz/hum emitting directly from the unit. I can hear the buzz/hum from a few feet away. It isn't noticable when I am playing music or watching a movie and hasn't had a negative effect on the preamps performance; however, it is annoying the shit out of me (excuse my language). I diconnected all components from the preamp, took it out of my rack, and brought it to another room in my house to see if I could duplicate the hum/buzz. After plugging the unit in another outlet, I still noticed this annoying sound. Unfortunately for me, Solo electronice, the manufacturer, went belly up half a year ago and the warranty is useless. The noise appears to be mechanical in nature and may be the transformer. I am asking for your assistance. What are your thoughts and does anyone know of a reputable repair shop in Orlando, FL or one that would allow me to ship the amp to them in the mail? Thanks in advance for your assistance.