Karaoke Forums

I KJed at a new place tonight.  I use an RSQ karoke player.  I split the RCA video coming out of the player into 2 RCA cables.  I plugged one into the singer's TV and one into the bar's TV.  When I plugged into the bar's TV, there was a loud humm coming from our speakers, even when the mixer volume was turned down.  The bar TV (I think) is linked to all the other TVs in the bar via cable.  Anyway, I obviously could not use the bar TV.  This happened to me before at another place.  In that case, I plugged a coax cable (using an RF modulator) and there was no buzz.  Is the humm coming from all the other TVs in that place?  Do I have to simply unplug the coaxial cable?  It is hard to get to (if not impossible) or is this a case of plugging the TV into the same power source as our stuff?  Can anyone help me on this?  Thanks

it could be interference from neon beer signs, unshielded cables in their video system, a bad RCA or broken Coax cable etc... it would be a matter of eliminating each possibility one by one from your system to their system...

Possibly a ground loop hum.  Assuming the singers TV isn't on cable, and the bar sets are on Cable.

The RCA cables were all brand new.  I've had this problem before.  Now that I think of it, it could be because the coax is plugged in.  The trouble is, it's hard to get to.  I think I might ask to have connector and loop it out to where I can reach it and then unplug it, then plug in the RCA cables.  I was also told I might need a ground loop isolater, whatever that is.  Am I on the right track with this stuff?

If the bar television sets are cable, that's an earth ground.  Possibly the "Singers" television, and your equipment is safety ground.  Assuming this to be the case, there's now a voltage imbalance.  (I'll defer possible solutions to someone with more tech knowledge than myself)

You need to check one of these out.  It goes your main power cord & is the safe way to lift a ground.

http://www.ebtechaudio.com/new.html

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Had a similar problem at home when I connect my cable box to my computer/karaoke rack.  You have a ground loop problem.  Use what Lonman recommended or get a 'Ground Loop Isolating Audio Cable' from Radio Shack for $16.  I use one of these and it works flawlessly.  I've put them on all of my video equipment in my rack so if I have a ground loop problem off connecting to the house video system it keeps me from having any problems.  $45 in cables solved hours of headaches and creative hookups. (They were $14.95 when I picked them up).

Hate to be master of the obvious here, but a ground loop would not go through your speakers if the volume was all the way down. It sounds more like you are connecting your video RCA cable into a video on one end and a stereo on the other end or even possibly a video in to another video in (or out/out) Check the connections to make sure this isn't the problem!!  Also, I have found that all RCA Y adapters do not handle video signals, so this may be the issue. You need one that is mono all around, and not stereo to a mono.

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C Mc
KJ, FL

Sorry to disagree, but yes it could/would go through the speakers with the volume down if there was a bad ground somewhere.  I especially have experienced them with bad cable systems ie hooking into the central system to hit all tv's but mostly due to bad power grounds in the building wiring.

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This happens often if one uses Notebooks to DJ / KJ. I use a line conditioner on all my equipment and ground loop isolators on my notebooks.

Power is very unpredictable in bars here most havn't been rewired in years and Neon almost always adds line noise to ground.

If cable tv was installed correctly it is earth ground. Power generally is not. This can cause a problem between 2 seperate grounds.

Solution:
1 disconnect tv from cable
2 use an rf converter vs rca
3 Buy a good furman line conditioner and ground loop isolators.

I can't disconnect the TV or use an RF adapter.  The back is of the house TV is impossible to get to.  I will try the ground loop isolator first and if that doesn't work, the device Lonman suggests.

I don't use a laptop.  This is just a regular karaoke player.

A bit technical post here. A hum can come from one of two sources: radiative or conductive. When the hum is conductive, it is a signal that travels through the ground plane and effects the audio signal. Typically these are harmonics or derivative of the sampling rate frequency (for CDs usually 44.1KHz or multiple of that on over sampling). You can fix this one by using the ground isolation method that is mentioned above. Typically isolating the ground from the offending signal emitter would fix this easily.

If that does not work, you may have an isolated ground problem. What that means is that the ground voltage level of one device may not be the same as other devices. Usually, that problem is eliminated if you plug all your devices in to a same power strip or a same outlet. If there is a hum and you have your devices plugged in to different outlets, make sure your ground level is all the same on all outlets. You will see this kind of problem specially on outlets with two prong plugs. Ones with three prongs supposely mean a true ground for all plugs but depends on how they connect it, some may be isolated and not truly grounded.

Lastly, it can be a radiative signal that interferes with your audio path. This is typically at 60Hz or harmonics of 60Hz, which is the frequency of the AC power. Typically, when a coil or inductors are near a non shielded cable, you will hear the 60Hz hum through that cable.  As mentioned before, neon beer signs, unshielded large power cables or unshielded speakers emit a lot of these signals that produces a hum. One way to fix this is to use shielded cables and make sure that the ground pin is touching a ground area on both sides of the cable. One cheap way to test this is to wrap an aluminum foil around the cable and make sure it touches the outer sides of connectors on both sides. If the hum disappears, then it's most likely the radiative inteference. If that is the case, using a well shielded cables should eliminate any radiative interference.

I hope some of this boring technical mumbo jumbo helps you fix that problem.

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Seize the day and SING!!!

I simulated this problem at home last night with my TV.  Same hum, until I plugged in my new $16 ground loop isolator I got from Radio Shack.  After that, the hum was completely gone, and the sound coming from the karaoke player was perfect.  Hopefully, I get the same results at the bar.