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
mofojo OP
2,314 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. 
mofojo OP
2,314 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. 
oldhvymec
5,101 posts
 
Wow.. you said you turned the gain down and the noise went away?

There is enough gain without the gain turned up on the A21, isn’t there?

The same circuit or at least rail at the main will help, too for future noise.

No need to start making more noise. :-) You'll get it..
lak's avatar
lak
4,751 posts
 
@mofojo, I think you will find the answer to your question here: 
https://rel.net/blog/2018-01-04/how-to/how-to-connect-my-rel/?utm_campaign=2020-12-25_broadcast_cont...
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