Low level hum only with lp playback

Jmc

to be fair that was my static issue. That was solved with the deerskin mat. The bum is new. 

john,

correct the hum only starts once the needle touches the moving vinyl. And you might be right about the hum being mechanically induced. I moved the subwoofer - only an inch - and it seems the hum is now gone. Due to my space limitations, my subwoofer is adjacent to my rack. It's never been a problem since I have a concrete floor, but a couple weeks ago I tweaked the subwoofer settings to a higher crossover point so the bass is more prominent now and I seem to get more subsonic woffer flutter. I guessing being too close to the rack may have caused a feed back issued with mechanical vibration and the TT translated that into hum. That's my best guess anyway. 

Magnetic field? Who knows, could be a lot of things...

Sounds like you’ve isolated your problem, but my recommendation for the sorbo under mat still stands. I find it dramatically deepens the sound field along with extending it vertically. For instance, now when listening to Moby Dick live on The Song Remains The Same the perspective is standing in the field center stage looking up at the band. With my 8’ ceilings the image is a quarter hemisphere extending past 90 degrees to either side arcing overhead with back hall sounds on some recordings appearing behind the seating position. Each instrument is easily defined in space to the extent you can tell when the lead guitarist for example turns to his right or left.

I’ve made other modifications to dampen the big Kenny, will share them in another thread if anyones interested, but I have to say the synergy of the Grace arm with the Grace cartridge showed it to be one of my most fortuitous purchases to date.

Martin

HI,
I had VERY similar problem, 120 Hz predominant noise + ONLY when record playing.  Turned out to be mechanically induced -- by vibration from the motor pod (physically separate) transmitted by the underlying shelf to the turntable/tonearm.  Banished by a mousepad under the motor pod; recently replaced the mousepad by Herbie's thick Grungebuster dots.
Good luck,
Harvey