2. analog
  3. 126134-46

Low level hum only with lp playback

Basic system:

VPI Prime turntable (cart is a Dynavector 20x2L) with
Purest Audio interconnects ( with integral ground wire connected to phono pre) to
Parasound JC3+ Phono Pre with
Cardas Clear Light Balanced Interconnects and separate ground wire connected to
BAT Preamp
REL R-r328 sub

I use an Eagle PSU with Roadrunner tach for speed control. 

So I'm getting a low level hum ONLY when the record is playing. You can hear the hum on the lead in groove - the sound gets louder as the volume goes up even if the music hasn't started.  However if the needle is lifted the hum goes away. 
I played around with the ground wires locations to no avail.
I've checked the leads to the cart for tightness and to make sure they are connected completely -they are. 
I've moved the speed control equipment to make sure they are no interfering. 
All my connections are tight. 

last_lemming

Showing 3 responses by last_lemming

last_lemming OP
632 posts
 
I have a deerskin mat and my cart is I good condition as far as I'm aware 
last_lemming OP
632 posts
 
 I've tried every which way - all on, all off, some on, some off, in all cases I can't get rid of the darn hum. 
last_lemming OP
632 posts
 
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. 
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