Originally Posted by Ladeback
I take it it is a powered sub? I have 15" powered subs built into my towers and I have a ground plug adapter on on my left speaker and now I have a hum in my right. I need to get a ground plug for it now. I hope that will fix it or I will just have to turn up the volume more.
Glad you figured that out. Those hums can be fun to chase down.
Yeppers. My Rythmik FV15HP's are powered. Thus is the tale of the ground loop...
It all began when the theater was being calibrated back in Nov. During the initial playback at reference level with only 2 channels active, the power source was tripped. Knowing right away that the theater would require more power, I called my electrician and he let me know he'd be on-site the following Mon (happened on a Sat).
After spending about an hour or so running the new outlets to the A/V closet, everything seemed to be going as planned! Then it began...
My front left tower had a nasty crackle sound to it. I immediately thought this was a ground loop issue. I had my electrician come back out and we tried many many different things, including making sure everything in
the house was run in parallel, to get the crackle resolved by no luck. Finally, as I had once before tried swapping out the RCA cable from my receiver to the miniDSP, I tried one more time as that would be considered "low hanging fruit". TA-DA! It fixed the front left tower!
However, in the process of doing whatever we did, my subwoofers now had that ominous, low hum sound. I believe unless you were listening for it, you likely wouldn't recognize it. But I knew it was there and would hear it every time I got through watching something. Once I called attention to it, anyone else in the room would then hear it. My electrician was out several more times and we tried many other things to try to isolate the problem.
Troubleshooting went on for several weeks when I had the time and really didn't put much effort into it now as I thought it I was stuck with it as tried so many things! I tried unplugging the HDMI's, RCA's all the equipment from the outlets to see what would make a difference. Nothing though.
My electrician stopped by again last week to look once again at the electrical because mind you, before the new outlets were installed, there was no hum. I know I have given the poor guy headaches trying to figure this out! We decided to call Rythmik to see if we might have overlooked something. Following their instruction of unplugging all HDMI cables (yet again after previous attempts) as cable boxes are a likely culprit, they also mentioned the cheater plugs (3 prong converter to 2 prong eliminating the ground) as the subs are grounded internally. As my electrician was in the room, he mentioned that he had just got done disconnecting the ground connection from those outlets the subs were plugged into which should've yielded the same exact result. Rythmik also mentioned to try a different audio cable.
After they said that, we turned the subs sideways to access the speaker cable and noticed if you were to slightly move the RCA cable, it would make a difference in sound and not in a good way! The humming would get louder. So went to Best Buy this past Sat to get another RCA cable that would reach from subwoofer to miniDSP/receiver. Swapped out the cables but no luck. At this point, I was really discouraged as I thought I really was stuck with the ground loop issue.
I kept going back to thinking it had to be something with that outlet that was installed because when I would unplug the LCR amps from outlets, that seemed to make a bit of a difference. As a last resort, I went to Lowes yesterday (Sun) and picked up a few cheater plugs. I thought, perhaps seeing if the ground issue might be with those outlets so tried plugging in the amps with the cheater plugs into those outlets. I couldn't believe it as it still didn't help!! I even tried running those amps through a power conditioner but nope, nothing as the hum was still there.
So there I sat pretty discouraged and was putting the cheater plugs back in the package to take them back to Lowes when I thought, you know I have them here and I know we disconnected the ground wires from the outlets and that didn't help, but might as well try putting these plugs on the ends of the subs and hook them in and see what happens. AND LO AND BEHOLD IT FIXED THE ISSUE!!!!!!