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Help with constant buzz to mixer

B

BLDun

macrumors regular
Original poster
Jan 22, 2005
164
0
I have a PowerMac G5 that I use at the church to run videos, slides, etc. Problem is that the sound from the computer to the mixer has a constant and annoying buzz. I have it hooked up with the 1/8" stereo jack out of the back of the computer and then dividing to a red and white rca plug into the mixer board. No other channel on the board has a problem except the one from the computer. When I record the morning services the buzz is present on the recording as well. Is there another - better - way to make this hookup or is there a solution?

Thanks
 
Sounds like you need a line out dac. Something like hrt music streamer, or any cheaper alternative that will line out the audio to an external dac that's free of any noisy computer interference. Does the mixer have its own amp?
 
The mixer has its own amp. It is a 32 channel Peavy. Upon further investigation I found that I have that buzz even when the computer is shut down. Just the fact that the line is hooked to the computer produces a buzz in the board. No matter what channel I move it to or how I hook it up, it still buzzes. I tried another 1/8" plug that is had but same results. Wonder if the 1/8" recepticle on the computer is bad possibly?
 
To me it sounds like a grounding problem with the computer.

does it still buzz with the computer unplugged from the mains or with the 1/8" plug unplugged from the computer or plugged into an iPod?

Do you have a stereo DI box and RCA -> 1/4" jack adaptors to try going through a DI box and lifting the ground switch.
 
OK Upon further investigation here is some more info. If I have the 1/8" plug in the back of the computer it always buzzes in the sound system, even if the computer is off or unplugged. I hooked up my laptop to the same 1/8" plug and it is completely quite; absolutely no noise at all. Plays everything crystal clear. So do you think the 1/8" plug on the back of my G5 could be bad?

Mroddjob, what is the DI box you are referring to? Right now the hookup is from a 1/8" stereo plug that has a factory build change to rca plugs and then they are hooked to regular 1/4" adapters that plug into the sound board.
 
DI box: http://en.wikipedia.org/wiki/DI_unit
They're used to convert unbalanced signals into a balanced microphone type signal, connected with a microphone XLR cable.
DI boxes usually have a ground lift switch which can help reduce mains 60Hz buzz (essentially caused when two separate things connected to the mains ground i.e desk and mac and there is a bad ground connection somewhere causing a kind of loop from the ground all the way through the connection between the desk and mac)

Although it actually sounds like you might be right in thinking the plug on the back of the mac is bad and might not be a mains loop buzz. What kind of buzz is it? Is it a low rumbling kind of buzz, or more like a harsh bee kind of buzz a bit like if you press your finger on the 1/8" plug with the volume turned up?
 
Well, I finally found the problem. Don't ask me to explain it all but here's what happened. I found that when I touched the metal case of the computer with the 1/8" plug it created a buzz so I'm thinking ground problem - even tho the computer was not plugged in. So I hooked an extension cord to the computer and began finding another receptacle to plug it into. In the sound booth there are four quad receptacles for various things such as CD players; Tape players; the computer we use to record on, etc. When I began experimenting with plugs nothing changed until I had to unplug the monitor for the second computer we use to record the morning services. The instant I unplugged it the buzz went away. I moved it to a plug in strip I had available and whalaa!!! No more buzz. I have no idea how the monitor from one computer could be creating buzz through another on a totally different receptacle system, even when it's unplugged but it works beautifully now.

Thanks for your help!!
 
Resurrecting this thread because I am having the same problem. I've had my setup in my basement and on gigs for a long time. It was until today that I set everything back up after a gig and now I have this loud buzz on my backing tracks going from my MBP's 1/8" out to 2 1/4" ins on the Mackie 8 channel mixer. Used to be crystal clear and now I hear a very loud buzz. I tried my DI box and it dampens the buzz a little but it's still there. Can't figure it out. I've tried other cables, unplugging things, even running the MBP on battery. Nothing seems to fix it and I never had the problem before. Am I missing something? I plugged headphones into the output and no buzz at all.
 
I have the simplest setup ever... but I am a 17 year old trying to get a career in this type stuff. I have a tiny handheld mixer that requires a 9v battery and a plug. Then the cords from instruments. I plug the instruments in then the output to my laptop. Which all ends up going through a 3.5 mm male aux end. When I turn the mixer on and hit record on Audacity on my laptop it has this buzzing sound, you can't even hear any instrument. Please help asap!
 
BLDun said:
I have a PowerMac G5 that I use at the church to run videos, slides, etc. Problem is that the sound from the computer to the mixer has a constant and annoying buzz. I have it hooked up with the 1/8" stereo jack out of the back of the computer and then dividing to a red and white rca plug into the mixer board. No other channel on the board has a problem except the one from the computer. When I record the morning services the buzz is present on the recording as well. Is there another - better - way to make this hookup or is there a solution?

Thanks
Click to expand...
I have been running a GoToMeeting app through a USB Codec Cable to a Peavy mixer. There is a slight buzz until GoToMeeting is initiated - and then a high-pitched hum that is a complete distraction to the speaker. After exhausting several different cables and connections, I finally figured out how to eliminate it.

The problem is bringing vocals across an analog mixer and sending them into an iMac digital port. Meanwhile, GTM is also sending a digital feedback into the analog mixer, then to the amp and speakers. In spite of the digital port on the mixer, it doesn't do what it needs to. Thus, I finally laid hands on a Focusrite Scarlett Solo (3rd Gen) USB Audio Interface unit that ran $119. It converts the analog to digital coming to the iMac. ALL background noise is gone. Note - after installation, reboot the machine, or you will think it is not working for you. Make sure you select the Interface on your input settings, both on the iMac and in the GTM settings. You can continue to use the USB Codec cord for audio out.
 
Had the same problem when I used the line out to my home theater system. Amazon sells a isolation gizmo for less than $10, will solve your problems.
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