Buzz When Video Connected

 

New member
Username: Mlkluther

Post Number: 1
Registered: Oct-05
I need some help. I have a BenQ DLP Projector and I am setting it up to use in our church. I need to use a VCR and DVD player. I want the audio from the VCR and DVD player to run through our sound board and the easiest way for me to do this is to run it through a microphone jack we have in the wall. So I bought a Y adaptor that goes from RCA to 1/4 inch plug. Then I bought another adapter that goes from 1/4 inch plug to xlr (microphone end). It works great except when I plug in the video cable into the VCR or DVD player I get this annoying buzz. When I unplug and remove the video cable (RCA or S Cable) the buzz goes away.

So all I can figure out is that the Video is interfrering with it somehow. I have shielded cables.

I can't figure it out. Anu help would be very much appreciated!
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 6386
Registered: May-04


First you have to tell me whether the noise is a 60Hz hummmmmmmmmm, or a higher frequency buzzzzzzzz. Just checking because most people mistake the two.


 

New member
Username: Mlkluther

Post Number: 2
Registered: Oct-05
I don't know. How do I tell between the two hums and buzzes?

Also, after doing some research I am wondering if it is a "ground loop." Also, I hear that dimmer switches can cause problems. The room in our church has 5 dimmer switches on the wall that I plug into (both the power outlet and the mic jack). Perhaps this contributes to the problem?

Anyway, If I am guessing I am going to say it sounds more like a buzz than a hum. But I am not sure to what I can compare it.

Thanks for your help!
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 6397
Registered: May-04


A hummmmmmmmmm is just that. A 60Hz low frequency tone.

A buzzzzzzzzzz is higher pitched.

A hummmmmmmmmm is caused by a ground loop or ground problem.

A buzzzzzzzzzzzzz is (usually) caused by RFI (radio frequency interference).



If the room has light dimmers, that is more than likely the problem and the noise is a buzzzzzzzzzzz. Turn off the dimmers and see if the noise goes away. If it is RFI from the dimmers, there's not much that can be done easily other than not use the dimmers. That may not help much since dimmers in another portion of the building can be causing the problem also. To minimize an RF buzzzzzzzzz, you will need a choke. You can try a pro audio shop that specializes in sound reinforcement. They are the most likely place to have a choke that might do the job. If you can't find a choke easily, some of the better AC line filters/surge protectors contain RF chokes. I am talking "better"; a $10 surge protector from WalMart isn't going to cut it here.




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