Buzzing over amplifier

So this is a problem I haven't been able to figure out with our congregations sound system.

The sound system basically consists of microphones an Amplifier and computer, video camera, and also broadcast our live services on Zoom.

When you turn on just the Amplifier, all is quiet, as it should be. But when you start up the computer, you immediately start to get a hum and periodic static that starts quietly but gets more audible as the computer boots up.

All the sound/computer electronic 110v devices are plugged into a power conditioner. The amp is grounded, and that ground plugs into the power conditioner.

The hum and static have nothing to do with our microphones... all inputs are turned to zero (except the Master) and we still get the hum and static. Unplugging items from the amp and/or computer does not change the static. The only thing that seems to affect it is when you touch the ground wire that goes from the amp to the power conditioner.

So what does this point to? A bad ground at the electric panel maybe? Ground loop somehow? Static electric interference from the computer? I'm stumped.

 

I think you are on the right track thinking of the ground. As you've found it sounds like the computer is the culprit and having it on the same circuit or same side of the line conditioner may be the problem.

You have a separate ground line from the amp to the line conditioner? Does the amp have a three prong, grounded cord? If it does I would try removing the external/additional ground wire to see if that has an affect.

With an extension cord I would try plugging the computer into a different circuit. If that solves the noise problem I would try plugging it into the same circuit as the amplifier but upstream of the line conditioner. That way you would have the line conditioner between the computer and other components.

 

Good ideas... I'll take an extension cord next time I go.

 

Don't forget the little things.

The line from the computer to the amp. Change it out with another cable.

If you have another input on your amp for the computer, try using that 2nd input.

Are you using an external sound card/device like a Tractor Audio 2? If so, either replace it with another card or remove it completely & use the cheap device in the computer (Just to trouble shoot).

Lines & connections were my go to starting point. I'd start at the computer, replace any upsize or downsize connectors like 1/8 to 1/4 connectors etc. Then replace lines/cables. Eliminate or change everything from the computer to the amp. Then change inputs of necessary.

I agree that a few times I have changed outlets to a different circuit solved the issue. But using an outlet upstream of the amp would be something to try as Dane mentioned.

Could be the output from the computer itself. Try another computer and just play some music or audio from Youtube or something.

Again... the simple stuff. Try not to overthink so much that you miss the obvious.

 

Good advice on using an extension cord to prove and locate a ground loop. I did it many times. Would recommend disconnecting all other items while testing. There’s a slight chance the computer is not the source, but rather a connection point.

 

Tried removing the ground made no difference, tried the extension cord into a different circuit, no difference. The static goes away when you unplug the cable from computer output -> Amplifier input. Plugging into a different side does not help.

So we had an expert come and determine that we need a different module between the two. A Peavey 03001370 USB-P - USB "direct box" was recommended. Apparently the type we currently have is not adequate for reducing the type of noise we are experiencing from our computer. (Likely power supply noise or similar.)

 

 

A little late to the party. Many computers don't like the L and R channels combined directly.
Apple products are like this.

You could use a basic USB to 1/8" convertor or a full fledged direct box.
What you need to do is to eliminate the audio amp in the computers which any USB converter does.
The high frequency switching noise of the power supply can sometimes be heard too.

 

The USB direct box fixed the problem.