Get a ground cheater one of this gray plugs . Leave the amp grounded and then float the ground of each component in your system at the ac plug one by one, Leave your turntable ground wire attached to your phono stage or preamp while you doing this. Just make sure to turn everything of from one step to another . You will find the ground loop . Be calm and patient
Analogue question
As everyone else in the world this lockdown has been a change in "normal " behavior but has given many of us audiophiles plenty of time to listen to "our music " . Since I am planning to downsize my living space I have been going through various pieces of equipment to determine what I will keep and what I would let go . 5 days ago I have come across a maddening problem with my analogue set-up ! Everything sounds great until I want to play a record and before I even place the needle in the grove I get a serious hum through my speakers ! I originally suspected I was getting acoustic feedback because my amp was close to the speakers . Yesterday I moved all the equipment to a distance of 6-10 feet from the speakers and still get the hum when I switch to analogue. Starting to wonder if it is coming from the turntable itself but before I take the time and energy to reset a new rig thought I would post a question on this forum. Any help would be greatly appreciated . Set-up is as follows : Dual Golden turntable w/ortofon red cartridge , McCormack UDP player , Forte 2a preamp feeding Forte 4A amp , speakers are Vandersteen 1C , interconnects KimberKable Heroes ,speaker wire Nordost Blue and Tice power conditioner .