Bass Guitar and Buzz/Hum

[Soundman0001]

I mix at my church weekly, and we always have a problem with a buzz in the bass guitar channel, different guitars, different cables, different DI's, we still have issues! It is a total mystery to me... What could make this happen? The only thing we haven't tried is a different spot on stage, would that change anything?

Here's our current signal chain:
Bass Guitar
1/4" to 1/4" inch cable
Radial J48 Active DI
25' XLR Cable
150' Snake
A&H GL2800

Lately, I have just put a gate on the bass channel so that its not noticable in the house when they are not playing.

Thanks for your help!
-Alex

 

[thatactorguy]

Have you tried patching it into another channel, like maybe where the guitar or keyboard normally go? Could be that the channel itself has a ground problem, or it could be something in the snake. Can you go directly into the board without using the snake?

 

[SHARYNF]

Have you looked to see if it is a problem with the lower frequencies in your system and NOT the source. It is possible that you have a damaged subwoofer that is buzzing, Don't only check the input side but look at the output,

Sharyn

 

[epimetheus]

If I'm reading the OP's post correctly, he uses a gate to kill the buzz when the band is not playing. This tells us that it is definitely the bass making the buzz. Have you tried the ground lift switch on your DI? If the buzz is a ground loop hum, the ground lift switch should take care of it.

 

[Soundman0001]

Thanks for all of the replys so soon! I'll have to try out some of the different things tomarrow, I'll try running a line directly to the board and see if that helps, along with switching the channel on the board. I have tryed lifting the ground on the DI, it helps, a little, but it does not solve it. Hopefully we can solve this issue!

Thanks again!

 

[Anonymous067]

Oddly enough, I've actually dealt with this problem before. Ground/lift switch did the whole "bad to worse" difference. I also tried the whole "eliminate the problem" (change cables, DI, switch, etc etc). Anyways I ended up just gating it, just like the OP.

Instead of looking at the output of the board, see if the noise occurs in the monitors too. Or, listen to the channel PFL and see if you hear a buzz.

 

[derekleffew]

Try plugging the instrument amps into a different circuit or even a different outlet. I suspect there's a ground potential between the stage and the console. An isolation transformer, such as the IL-19, would likely eliminate the unwanted noise.

 

[SHARYNF]

If I'm reading the OP's post correctly, he uses a gate to kill the buzz when the band is not playing. This tells us that it is definitely the bass making the buzz. Have you tried the ground lift switch on your DI? If the buzz is a ground loop hum, the ground lift switch should take care of it.

Just to clarify, IF the problem is the low frequency signal in the output say caused by a sub woofer speaker rubbing or what ever, then the gating is not going to prove that it is an input problem since the sound will only occur when there is actually a signal in the low frequency spectrum causing the problem.

The fact that despite all the changes the problem is still there COULD mean that the problem is downstream in the signal path. Usually these problems are ground potential problems OR some shield cable problem that despite changing "ALL" the cables is still there.

Most likely it is in the cable going from the stage to the board OR a problem on the connector going into the board or the actual connector in the board.

sharyn

 

[epimetheus]

Just to clarify, IF the problem is the low frequency signal in the output say caused by a sub woofer speaker rubbing or what ever, then the gating is not going to prove that it is an input problem since the sound will only occur when there is actually a signal in the low frequency spectrum causing the problem.

Snip

While I don't want to argue about a problem that none of us can really troubleshoot very well since we are not there, I do have to say somehting. If there's a low frequency signal present when nobody is playing, then there's still the problem of what is creating that signal, irregardless of whether there's a "sub rubbing" or not. A sub would not be rubbing if there was no hum there to begin with.

In my experience, which is mostly non-professional musicians with lower-end gear, 90% of all lower frequency hums on instrument channels are some sort of ground potential difference.

 

[museav]

I think the first step is to get some additional information that might help narrow down the cause. Some of this has already been suggested, for example try plugging the DI output into a different channel and try connecting a different source to that channel. Maybe even try plugging the DI output direct into the GL2800 input and removing the snake entirely. Make sure you are getting phantom power to the DI and so on. The general concept is to divide and conquer, determining the specific portions of the signal path or the particular situations that cause, eliminate or alter the noise.

Some additional information such as whether the noise is a low frequency hum or a higher frequency buzz might also help, as might information such as anything that changes the level or quality of the noise.

Is the snake permanent or portable? If it is permanently installed then it is less likely that the cable itself or the connections at the console would go bad and more likely that any snake related issues would be at the stage connection. If the snake is portable and constantly connected/disconnected and moved, then the likelihood of snake related problems increases both in general and in the potential points of failure.

 

[SHARYNF]

While I don't want to argue about a problem that none of us can really troubleshoot very well since we are not there, I do have to say somehting. If there's a low frequency signal present when nobody is playing, then there's still the problem of what is creating that signal, irregardless of whether there's a "sub rubbing" or not. A sub would not be rubbing if there was no hum there to begin with.

In my experience, which is mostly non-professional musicians with lower-end gear, 90% of all lower frequency hums on instrument channels are some sort of ground potential difference.

Sorry for my confusing post
I was trying to make a diffence from the Input (meaning the Bass guitar/amp di etc and the rest of the system Ie could be the snake, input cable, connector on the mixer etc. These could be causing a continuous signal that could be causing the noise and the gating could turn it off.

I agree it is almost all times some sort of ground potential problem. But sometimes it can be a bit further up the channel path. It obviously also is important where the gate is placed

Sharyn

 

[TimmyP1955]

I've had a few bass rigs that gave me a ground loop buzz that could be solved only by using a passive DI (I normally use Radial Pro48s), or by plugging the bass rig into a mains outlet that was at the same ground potential as the PA.

 

[FMEng]

I didn't see a guitar amplifier mentioned, but if there is one, it could be a contributor to the problem. I have encountered a few instrument amps that have a tendency to create strong, 60 Hz magnetic fields a foot or three around their power transformer. In that case, you have to get the DI box (and the guitar) sitting far enough away, or in a null, to prevent hum getting induced into the output. Most DI boxes use transformers, which make them susceptable to stray magnetic fields.

I have also encountered instrument amps that are defective and have too much AC leakage current to chassis ground. It's going to go somewhere. If the ground pin on the AC cord is gone, that'll make the situation worse. Ground the amp properly, and use the ground lift switch on the DI box.

 

[TimmyP1955]

I didn't see a guitar amplifier mentioned, but if there is one, it could be a contributor to the problem. I have encountered a few instrument amps that have a tendency to create strong, 60 Hz magnetic fields a foot or three around their power transformer. In that case, you have to get the DI box (and the guitar) sitting far enough away, or in a null, to prevent hum getting induced into the output. Most DI boxes use transformers, which make them susceptable to stray magnetic fields.

I have also encountered instrument amps that are defective and have too much AC leakage current to chassis ground. It's going to go somewhere. If the ground pin on the AC cord is gone, that'll make the situation worse. Ground the amp properly, and use the ground lift switch on the DI box.

Good points.

If the amp has a two prong mains lead and a ground switch (as old Fenders do), have the mains lead replaced with a three-prong that's grounded to the chassis, and have the switch disabled and its "death cap" removed.

 

[browjj01]

Hey I'm having the same issue. The Bass guitar is having a high frequency buzz come through it when no one is playing but when I run a 6 string electric guitar through the same system it does not buzz and we've tried 3 or 4 different basses and they all do it any ideas? I'm trying the gating for now to cover it but I want to eliminate it if I can.

 

[DiscoBoxer]

Likely one of the issues that have been mentioned above. Cheap cables, poor grounding in your power source outlet, missing 3rd (ground) prong at amp, etc.

Have seen a lot of lower end bass guitars with active pickups magnify any problems that may have been slight before.

Check everything inline, then as FMeng stated, look at the not so obvious things such as electro/magnetic induction sources near the Bass (pickups), Bass Amp, or DI. Things such as Lighting dimmer packs or even power distribution panels. Another note, move the DI away from the amp itself to avoid the cab speaker magnet and verify that none of the cables inline have excess lengths that may be looped near any of the above mentioned magnetic fields. I once had a player with a very long cable, coil half of it in the back of his Amp right near the speaker magnet that gave me headaches.

Good luck!
Disco

 

[DuckJordan]

What kind of bass amp is it... I have found with the low end bass amps they have a huge tendancy to give you a buzz on the second input what i have found solves this problem is to take an adapter such as an RCA to 1/4" or 1/8" to 1/4" and just plugging it into the second input on the bass amp. I'm not sure what causes this other than a cheap way to put the second input in is to make it an inline input... again this is for cheep like $200's or less area...