How do you track down a buzz in the PA?

[Jehos]

I had a nasty buzz on stage at my last gig and I'm trying to figure out how to track it down.

My setup is pretty simple--Tobias Standard 5 plugged into a Markbass 2x10 combo. The direct out from the amp went to the PA.

I didn't get too much time to troubleshoot on stage. The bass is new to me. The buzz got louder and quieter with the volume knob on the bass. The ground lift on the amp did nothing to get rid of it.

How do I track down the buzz, and what can I do to fix it once I find it?

[ggunn]

Originally Posted by Jehos

I had a nasty buzz on stage at my last gig and I'm trying to figure out how to track it down.

My setup is pretty simple--Tobias Standard 5 plugged into a Markbass 2x10 combo. The direct out from the amp went to the PA.

I didn't get too much time to troubleshoot on stage. The bass is new to me. The buzz got louder and quieter with the volume knob on the bass. The ground lift on the amp did nothing to get rid of it.

How do I track down the buzz, and what can I do to fix it once I find it?

Did you try disconnecting the direct out? Direct outputs are notorious for being noisy. I carry a groundlifted XLR connector that I put in line when I get a bunch of noise; it helps a lot --- sometimes.

[Hoover]

You track it down via a rigorous, methodical process of elimination, starting at one end of the signal chain and only proceeding down the chain after each component is verified as unequivocally not the source of the buzz. If you want to be really swanky and thorough you use dummy loads (essentially a pass-thru connector with a resistor tied to ground) at each stage, but simply removing or replacing each component can tell you a lot about the origins of the problem.

[SteveC]

Originally Posted by Hoover

You track it down via a rigorous, methodical process of elimination, starting at one end of the signal chain and only proceeding down the chain after each component is verified as unequivocally not the source of the buzz.

Truth. A pain in the butt, but really the only way.

[ggunn]

Originally Posted by SteveC

Truth. A pain in the butt, but really the only way.

True, but I'd check the direct out from the bass to the PA first. Very often that is the culprit.

[SteveC]

Originally Posted by ggunn

True, but I'd check the direct out from the bass to the PA first. Very often that is the culprit.

Agreed.

[T-Bird]

Hi.

Originally Posted by Hoover

You track it down via a rigorous, methodical process of elimination, starting at one end of the signal chain and only proceeding down the chain after each component is verified as unequivocally not the source of the buzz.

Again, ^ this.

While passable, the DI's on heads are quite often either discrete or IC based. Only a true galvanic isolation of a transformer will help in most situations. Ground lift will only reduce the hum in most cases if there's no galvanic isolation.

IMLE, 9 times out of 10, the buzzes and interferences can be traced to the lighting system and/or the other appliances (inductive loads mostly) on the same circuit.

Regards
Sam

[Jehos]

I didn't try disconnecting the direct out. That was the only way I was getting sound at the time, we were having bad feedback issues also so I had to keep my amp turned *way* down.

I'll try that out for next time. One other thing I forgot to grab for the gig was my direct box. I'll be sure to toss that in the gig bag next time so I have an option to take the amp completely out of the mix.

[Geddyfleaharris]

Try everything the other posters have said especially the direct line. But in truth sometimes it will be beyond your control. A refrigeration unit kicking in at a club can cause havoc with the buildings electrical system depending on the age of everything. That type of thing is simply out of your control.

As long as your gear is good in a familiar environment then after that you are sometimes just at the mercy of the venue's electrical system.

[ggunn]

Originally Posted by T-Bird

Hi.



Again, ^ this.

While passable, the DI's on heads are quite often either discrete or IC based. Only a true galvanic isolation of a transformer will help in most situations. Ground lift will only reduce the hum in most cases if there's no galvanic isolation.

A handy thing to have in your gig bag if you use a DI out from your bass head is a balanced line ground lift. It's a connector that is XLR male on one end and XLR female on the other which isolates the chassis of your amp from the shield of the line. It won't solve your problem 100% of the time, but it's a tool to try.

[jaywa]

In any event, know this... anytime there is a buzz, feedback, etc. of any kind in a P.A., the sound tech will invariably assume that you -- the bassist -- are at fault. If you're lucky, they'll go to the trouble of proving whether it is in fact you or not. If you're not lucky, they'll just take you out of the mix and assume they've solved the problem.

I speak from years of experience on this. 9 times out of 10, it wasn't me after all.

[ggunn]

Originally Posted by jaywa

In any event, know this... anytime there is a buzz, feedback, etc. of any kind in a P.A., the sound tech will invariably assume that you -- the bassist -- are at fault. If you're lucky, they'll go to the trouble of proving whether it is in fact you or not. If you're not lucky, they'll just take you out of the mix and assume they've solved the problem.

I speak from years of experience on this. 9 times out of 10, it wasn't me after all.

I've got a couple of things to say about that.

One, if there's a buzz or hum in the PA that's there after the band has set up and it wasn't there beforehand, and the bass is going into the PA through a DI, a whole lot of the time it's the bass amp (not the bassist; it's not personal) that is contributing the noise. It's a fact of life and that's what I would check first.

Two, I (and all the sound men I know) will attempt to solve the problem rather than just pulling the bass out of the mix. Pulling the DI and setting a mic just takes a minute, and pulling the bass out of the mix by taking down a fader usually won't solve a grounding problem, anyway.

[TomB]

Originally Posted by ggunn

I've got a couple of things to say about that.

One, if there's a buzz or hum in the PA that's there after the band has set up and it wasn't there beforehand, and the bass is going into the PA through a DI, a whole lot of the time it's the bass amp (not the bassist; it's not personal) that is contributing the noise. It's a fact of life and that's what I would check first.

Two, I (and all the sound men I know) will attempt to solve the problem rather than just pulling the bass out of the mix. Pulling the DI and setting a mic just takes a minute, and pulling the bass out of the mix by taking down a fader usually won't solve a grounding problem, anyway.

I'd pretty much agree with what's been said, except most sound folks IME, if time's running short, will just throw in their own DI out of your bass to sub for your amp's DI, and save the mic in case their DI has issues as well. Sometimes it works, sometimes not. It's one reason so many folks on this forum buy their own remote DI's to carry around... one less uncertainty.

[ggunn]

Originally Posted by TomB

I'd pretty much agree with what's been said, except most sound folks IME, if time's running short, will just throw in their own DI out of your bass to sub for your amp's DI, and save the mic in case their DI has issues as well. Sometimes it works, sometimes not. It's one reason so many folks on this forum buy their own remote DI's to carry around... one less uncertainty.

In any case, the sound man is there to be your liaison with the PA and the venue. It's better to cultivate an atmosphere of collaboration than to assume an adversarial position.

If the bass amp's integrated DI has a noise problem, and ground lifting the line doesn't fix it, I will usually ask the bassist whether he'd rather use an instrument DI or mic. You're right though; if time is short and the sound man is addressing several problems at once, the show must go on and sometimes less than ideal solutions must be applied. Carrying your own set of solutions is a wise move.

[jaywa]

What I've learned works best is to take a pro-active (but collaborative, not adversarial) position if there is hum or buzz during soundcheck. First thing I'll do (assuming I'm using my own head with its integrated D.I.) is hit the ground lift switch and ask the sound guy if that fixes the problem. If it does, we're good to go and everyone's happy cause I manned-up and as a result the problem was fixed straight away. If it doesn't fix the problem, then my rig has been ruled out first and they can leave me alone and move on to isolating the real cause of the problem.

It just got a little annoying after awhile knowing I had pro-grade gear that was well maintained, and yet every time there was a noise issue in the P.A. they'd assume it was me first thing.

[ggunn]

Originally Posted by jaywa

What I've learned works best is to take a pro-active (but collaborative, not adversarial) position if there is hum or buzz during soundcheck. First thing I'll do (assuming I'm using my own head with its integrated D.I.) is hit the ground lift switch and ask the sound guy if that fixes the problem. If it does, we're good to go and everyone's happy cause I manned-up and as a result the problem was fixed straight away. If it doesn't fix the problem, then my rig has been ruled out first and they can leave me alone and move on to isolating the real cause of the problem.

Actually, that doesn't rule it out. If you disconnect your integrated DI and the problem is still there, then your rig has been ruled out. Plug it back in and move on.