2. amps-preamps
  3. 166076-3592

hum when hooking up sub to preamp

I have a Jolida Fusion Preamp and it's kind of noisy. It does have a musical full bodied sound which I like. I am hooked up to a Parasound A21 which has gain knobs. I have the gain knobs dialed back about a 3rd and this eliminates the hum to where you can only hear it from several inches away. When I hook up a sub from the XLR on the Jolida now there is hum coming from the main speakers again. I guess my question would be is there some kind of on way transmission xlr or rca cable where the noise would not travel back into the preamp? Would this even help. Any other suggestions to get rid of the hum here? 

Thanks
mofojo

Showing 3 responses by mofojo

mofojo OP
2,312 posts
 
Oh I also will mention when I run DAC direct into the Jolida I can hook up a sub from the DAC also and there is 0 hum so it's specific to the Jolida. 
mofojo OP
2,312 posts
 
Sub will not accept speaker level inputs. It's actually a Paradigm Servo 15 I blew up years ago. Using a Crown XLS 1500 to power the woofer directly. Also have a JL F113 I need to get fixed. I think an input cap is bad. 
mofojo OP
2,312 posts
 
I think I may have tried regular RCA but can't remember for sure so I will try that again. All the outputs from the Jolida Pre are on all the time, no switch. 
Hum does not change in volume from the gain setting on the sub.
If I turn the gain all the way down on the Parasound there is nothing when the sub hooked up coming out of the main speakers. 
I have 2 dedicated power lines in the system and the sub plate is on the other line. I'll try and put them on the same line and see what that does. 
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