Low level hum from sub-woofer

[mjt832]

I just purchase a sub-woofer that seemed to be working fine for a while. Now it produces a very low level hum when it is turned on. I tried everything. The only time it stops is when I unplug the connect cables that are going from my amp to my sub (or when I turn my sub off). In other words - I don't think it is the sub-woofer or the power. Like I said when I unplug the inter-connects going from my amp to my sub-woofer the hum goes away. Obviously that is not a long term solution - no signal/no sound. I already did a little research and some people recommended a "Subwoofer Isolation Transformer/Ground Loop Hum Eliminator." If that is the way to go will I need 2 of them (left and right channel)?

Anybody know if this would work or does anyone have any suggestions? Any responses would be much appreciated. Thanks in advance.

 

[lovinthehd]

Can you describe all the gear in the loop as well as what sub, particularly why you are using L/R inputs on the sub? How long ago did you purchase the sub? It had no hum for how long? Did you make any changes to the system around the time the hum started?

 

[mjt832]

Can you describe all the gear in the loop as well as what sub, particularly why you are using L/R inputs on the sub? How long ago did you purchase the sub? It had no hum for how long? Did you make any changes to the system around the time the hum started?

Thanks for getting back to me lovinthehd. I have a JL Audio (Fathom f1 12 v2) sub-woofer. I received that in April '22. I have a Parasound JC5 amplifier (that was purchased in February '22) and I have a pair of audioquest Yukon interconnects (2 meters) also purchased in Feb '22. I also have an audioquest line conditioner (I think it is called a "Niagara 1200). Nothing has really changed that I know of .... I did have the right channel cable coming from the amp going into the left channel input on the sub (so the left channel cable was also plugged into the wrong input on the sub : ) ) for a while. When I noticed my mistake I corrected the cable locations and that seemed to help a little bit. Thanks.

 

[lovinthehd]

The JC5 appears to be just a power amp....what is your pre-amp? Or is there a line-out on the power amp? I'd probably just split the signal from pre-amp to both your power amp and sub if you don't have a dedicated sub pre-out on your pre-amp. Too bad you already bought that junk Audioquest crap (I call 'em fraudioquest). The interconnects should work, I wouldn't bother with a power conditioner, especially theirs, and wouldn't put a power amp on one. Try this review for the Niagara

 

[mjt832]

There is a line outcoming from the power amp. There is no physical connection going between the pre-amp and the sub-woofer.

lol - to late on the audioquest. I really am not happy with their stuff seems over priced.

 

[lovinthehd]

Overpriced is putting it mildly, it borders on fraud (thus fraudioquest). What is the pre-amp you're using? Why connect the amp to the sub particularly instead of using the pre-amp? Have you tried not using the power conditioner in the loop?

 

[mjt832]

I am using a Bankert Labs Rhumba Extreme. It has 2 balanced outputs that I can connect to my sub"s inputs. That is the way I did it with my old system - went from my pre-amp to my sub (low level frequency inputs L/R) and then High Level outputs L/R on my sub to my AMPs inputs L/R. It worked great.

For the life of I don't understand why my current sub only has 1 out? I think I need 2 channels (L/R) output on the sub to plug both into the amp - other wise 1 of my channels on the AMP will be silent? I think I am forced to go from my pre-amp to my amp and then use the "Loop Outputs" on the AMP to connect to the sub. That is what they told me at Parasound anyway.

 

[mjt832]

I just checked the Sub again a little closer. That output is for a "Slave" connection only - if I want to have 2 subs in the room. I have to do it this way. I have no choice.

 

[mjt832]

Overpriced is putting it mildly, it borders on fraud (thus fraudioquest). What is the pre-amp you're using? Why connect the amp to the sub particularly instead of using the pre-amp? Have you tried not using the power conditioner in the loop?

Yes - I plugged it directly into the wall, I tried cancelling the ground (worked before for me). Nothing works. I am going to try an isolation transformer (whatever that is?) They are only $50.00 on Amazon. It will be worth the experiment if it works.

 

[lovinthehd]

I am using a Bankert Labs Rhumba Extreme. It has 2 balanced outputs that I can connect to my sub"s inputs. That is the way I did it with my old system - went from my pre-amp to my sub (low level frequency inputs L/R) and then High Level outputs L/R on my sub to my AMPs inputs L/R. It worked great.

For the life of I don't understand why my current sub only has 1 out? I think I need 2 channels (L/R) output on the sub to plug both into the amp - other wise 1 of my channels on the AMP will be silent? I think I am forced to go from my pre-amp to my amp and then use the "Loop Outputs" on the AMP to connect to the sub. That is what they told me at Parasound anyway.

I looked at the amp's manual and the lineouts are supposed to be suitable for a sub, but I'd still just use the preamp to the sub, and your preamp seems to accommodate such, balanced or unbalanced (didn't dig into the manual tho). Some sub amps provide connectivity for other gear, or even a crossover, some don't. That's why you buy gear that connects and serves best the gear you need/want, not the other way around. With a sub I'd want a pre-amp with bass management or at least a sub pre-out. You're summing it to mono thru the sub so you do need the L/R inputs (altho much sub bass is summed to mono in recordings anyways) since neither your pre-amp or amp can do that. Especially for the costs of the gear you bought....certainly has limited functionality.

 

[clubfoot]

In your owner's manual page 18 & 19 it describes the use of rear conntections. If you have a stereo preamp without an LFE OUT then use either both RCA (unbalanced) OR both balanced inputs. The unbalanced RCA inputs should not hum because internally they are optically connected in the sub. In my experience (F113 v2) the source of low level hum is further up the chain. I would unplug all equipment connected to the pre amp to see if the hum goes away,...and if it does add one component at a time until you find the source.