turntable " thump " sound when not running


Hi I have a question that’s been in the back of my to do list for the longest time so I decided to join the forum after reading so many postings over the years from this legendary community. :) I have a thump sound the same way it sounds when dropping the stylus on a record. it occurs about every 10-20 seconds or so regardless if the turntable platter is spinning or off. I am guessing its electrical? what causes this? I have a pretty decent setup yet modest compared to most of you guys in here and I think I shouldn’t have to deal with this thumping sound.  By the way this sounds only occurs on the phono.  the cd, tape, etc doesnt have this problem. 

Adcom GFP-750 preamp
Adcom GFA-555II amp
Jolida JD9 II
Music Hall 5.1SE TT (Sumiko Blue Point no. II)
LSA-1 Statement speakers

I have the turntable power supply adapter plugged into the back of the preamp power ports.
Should I move it to a different outlet? Maybe I just answered my own question.

128x128obeerbongkenobi

Showing 1 response by obeerbongkenobi

Thanks for all your feedback everyone.  I ended up unplugging the Turntable power supply from the back of the preamp and plugged it directly into the wall outlet and then turned on everything so i could listen for the sound and it was still there.  So then I started to jiggle the ground wire that runs from the turntable base to the Jolida Phono preamp and the hum would come and go.  then i noticed the end from the jolida pulled out completely and sound went away.  neither ground hum or the thump sounds!!.  I detached it from the TT as well and just took out the ground wire altogether.  Strange.