Stinkin Hum !!!!!

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Member Since: Nov 13, 2007

Ok, I built a studio last year to house all my stuff. I ran all new electrical service. I went to great lengths to insure I would not have any problems with electrical noise. Well I hooked up all my stuff (miles of cables) and all was well. I have a lounge area with a tv, dvd, stereo and video games. All that stuff is hooked to my vintage stereo system and sounds great. Well I have a pretty nice PA system (subs and all) and thaught Id hook the tv up to the PA. That way when watching concert dvd's I could have concert levels. Well thats when the problem happened. As soon as I ran rca cable to my mixer from the dvd, my PA and monitors started to hum. So I went out and bought monster cables. Same thing. I traced everything and could not figure out the problem. So I gave up. Well a year later (today), I decided to try again. I plugged this into that outlet, swapped cables, tried all sorts of things. So I unplugged everything and just plugged my dvd into the mixer and as soon as I plugged in a speaker, the damn thing started humming. I was getting really pissed. And then I said what havent I tried. I looked at the tv coax (my cable service) and said nah it couldnt be. I unplugged the coax and the noise went away. I can crank the PA up to 180db !!! and no hum !!!! The stinkin cable company is causing all the noise !!!

Now I have to plug in the cable to watch tv and unplug it to watch concerts. Anyone know of a cure. Does it sound like a contact cable tv and complain problem? They will say we dont trouble shoot PA noise. I know its a ground issue. Maybe if I ground the coax to an electrical ground ? Any help ?

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String bender
Since: Unknown

Dec 17, 2007 12:38 am

Please understand that I am by no means an expert. I seem to recall owning a power strip / surge protector that had a place to run both the cable and telephone lines through it. I do not know if this would help to ground your signal or not but its an idea to explore. Maybe someone with a bit more experience could answer this one.

Czar of Midi
Since: Apr 04, 2002

Dec 17, 2007 07:00 pm

Yep, two things contributing to that issue. Indeed the consumer level signal -10dB going into the mixer line inputs which probably are +4dBu. That will cause and issue to start with, not all to blame there though. But indeed the signal from the cable is always on. You need and isolation switch or similar to eliminate it. That way the cable can be disconnected from the circuit and all will be quiet. The simply switch back when cable is the featured fair. But the isolation box can also eliminate it entirely and you would then be able to watch cable at deafening volumes as well.

Since: Nov 13, 2007

Dec 21, 2007 05:51 pm

Yep. Ground Loop Isolators. Expensive little buggers. Im gonna try the surge first and if it doesnt work. Then its the little $50 isolator :) The cable guys couldnt help either. I figured as much. They never had anyone hook a PA up to a TV :)

Hold 'Em Czar
Since: Dec 30, 2004

Dec 22, 2007 08:16 am

do you have an "rca" "tape in" on you mixer? try hooking up to that instead..this will put things in the right level (-10)...also you should have your own dedicated volume knob for it, so you don't have to worry about messin' with your normal setup.

Since: Nov 13, 2007

Dec 22, 2007 12:05 pm

Yep. RCA tape ins. Thats where I have them. Ive tried other inputs also. I even took my smaller Mackie mixer and tried using it. Same thing. No matter where they are plugged in. But as soon as I hook up the cable tv, HHHHMMMMMMMMM !!! :) Hope to try the surge today.

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