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[Michael McCoy]

Need some new guy help,

I am a network engineer that was asked to help out fixing a few issues with sound at my local church. I know enough to have resolved all their issues but one.

So on the kick drum, bass guitar and two electric guitars, we have some noise on the channels. It’s not a ground loop and I can’t find what is bleeding into the channels. Killed all power in the area and still have the noise.

It’s also shown on the rta snapshot attached. The noise is across the entire band from 20 hz to 20k.

[Don T. Williams]

Need some new guy help,

I am a network engineer that was asked to help out fixing a few issues with sound at my local church. I know enough to have resolved all their issues but one.

So on the kick drum, bass guitar and two electric guitars, we have some noise on the channels. It’s not a ground loop and I can’t find what is bleeding into the channels. Killed all power in the area and still have the noise.

It’s also shown on the rta snapshot attached. The noise is across the entire band from 20 hz to 20k.

We need a lot more information.  What model is the mixer?  Is there an analog or digital snake?  Are all of these input signals from microphones, and if so which mics?  Are some of these DI boxes?  Is the phantom power (48V) on for these channels?  Noisy guitar (and even bass) amps are common, but if the same noise is in the kick drum channel that is odd.  If you unplug the inputs from the mixer is the noise still there?  How about when the "mic" end is unplugged?  More info please.

[Michael McCoy]

Mixer is a Roland VMixer M-400 with digital snakes. These are not mic inputs with exception of the kick drum.  Then a bass and two electric guitars. No Phantom power. The guitars come off of a DI box which is a rack mounted Behringer. If I unplug from the snakes or mixer the noise goes away. If I unplug the guitars 1/4 the noise is still there.

Mike

We need a lot more information.  What model is the mixer?  Is there an analog or digital snake?  Are all of these input signals from microphones, and if so which mics?  Are some of these DI boxes?  Is the phantom power (48V) on for these channels?  Noisy guitar (and even bass) amps are common, but if the same noise is in the kick drum channel that is odd.  If you unplug the inputs from the mixer is the noise still there?  How about when the "mic" end is unplugged?  More info please.

[Erik Jerde]

Mixer is a Roland VMixer M-400 with digital snakes. These are not mic inputs with exception of the kick drum.  Then a bass and two electric guitars. No Phantom power. The guitars come off of a DI box which is a rack mounted Behringer. If I unplug from the snakes or mixer the noise goes away. If I unplug the guitars 1/4 the noise is still there.

Mike

Isolate isolate isolate.  Use a different cable on the kick.  Use a different mic with the same cable and with a different cable on the kick.  That should show you the problem.

Do the same with the DI sources.  Use known good parts to replace each piece of the chain and find where your problem goes away.  Test for the problem after each replacement.

Use known good equipment on your snake to verify that there’s no issue with the input.

Some Behringer DIs have been known to be noisy when in proximity to some other gear so it wouldn’t surprise me if those are your culprit.

[Ken Webster]

Certainly, systematically isolating the various parts of the system is the way to identify the source of a problem.  Be aware that with analogue components, noise often relates to high resistances and bad connections, especially a cable shield.  Run an ohm meter over all suspect cables and clean and condition (such as Deoxit) all the plugs and sockets and make sure connections are tight.  Some cheap domestic audio cables just don't heve enough conductor in them or the wires are only press fitted inside the plug and are noisy.  Even a dry volume control pot can make for a noisy signal.

Ken

[Jean-Pierre Coetzee]

Need some new guy help,

I am a network engineer that was asked to help out fixing a few issues with sound at my local church. I know enough to have resolved all their issues but one.

So on the kick drum, bass guitar and two electric guitars, we have some noise on the channels. It’s not a ground loop and I can’t find what is bleeding into the channels. Killed all power in the area and still have the noise.

It’s also shown on the rta snapshot attached. The noise is across the entire band from 20 hz to 20k.

Pre-dominant 60Hz on the picture yet you are sure it is not a ground loop, did you check for pin 1 problems? That Behringer DI doesn't mean anything for isolating grounds, it works for impedance conversion but will very likely not solve a grounding issue.

Also check that the problem isn't the bass guitar itself. In one of our venues any bass guitar with a single coil pickup will buzz, more than likely the same thing will happen to an electric with a single coil pickup.

What model is the kick drum microphone and what does the noise on it sound like, this is the one that baffles me. The guitars I can understand the kick drum I don't.

[Mike Caldwell]

Are you using any cheap eBay special mic cables?
Many of those have pin 1 tied to the XLR shell, that can cause noise issues. 

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