solving a buzzy signal

Tim Jones · From: Oakland, CA

Hey Gang â€” Long-time reader, first-time poster here! I'm new to lap steel guitar (or ANY guitar for that matter), and have just been teaching myself with online tutorials, youtube videos, etc.

My guitar is a random custom lap steel I bought on ebay. It has no brand name. Confused

Often I get a loud buzzing noise in my guitar pickup. It's a big nasty 60hz humm.

I have a battery-powered Electro Harmonix headphone amp -- this actually works great! Some quiet buzz, but nothing loud enough to be problematic.

However, I'd like to be able to plug my guitar into a mixer. I have a Behringer XENYX802. Initially I tried plugging the guitar into the microphone input and using the XENYX preamp to boost the signal. This resulted in a real loud buzz.

I've tried using two different DI boxes. First, a cheapo Behringer DI400P. This didn't help -- I still get a lot of buzz. Second I tried a fancier Radial Pro48, hoping the phantom-power boost would solve the problem. No luck.

I'd also like to use an overdrive pedal for that nice bluesy sound. I'm trying to use a Behringer Vintage Tube Overdrive -- but of course it adds *even more* buzz to the signal.

What do y'all think? Is my guitar just crappy? Or is there some technical strategy that might fix this that I haven't considered? Why would I be getting buzz in the mixer but not in the headphone amp?

Apologies for posting yet another buzz question to a forum that already has too many! Massive thanks in advance for the advice.

=Tim=

Paul Sutherland · From: Placerville, California

Is this happening in an older building with questionable wiring? Single coil pickups can exhibit this problem in such an environment. Do you know if your pickup is single coil or a humbucker?
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Tim Jones · From: Oakland, CA

It is a somewhat older building, so perhaps that's part of the problem.

The pickup looks like it has two coils -- I think that means it's a humbucker?

Paul Sutherland · From: Placerville, California

That certainly looks like a humbucker. I suppose it's possible that only one side of the pup is working so it's effectively a single coil, but that seems fairly unlikely. I suggest you take the lap steel to your local Guitar Center or other music store and plug into a regular guitar amp and see what happens. I'm running out of ideas.
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It don't mean a thing if it ain't got that swing.

Larry Jamieson · From: Walton, NY USA

Have a qualified electronics repair tech look at the wiring inside your guitar. Could be a loose ground wire from the bridge, or maybe somebody wired the input jack backward.

Jack Hanson · From: San Luis Valley, USA

If the problem goes away, or is greatly reduced, when your hand comes into contact with the strings, try this: Slack off the strings to the point you can unscrew the bridge and/or tailpiece and verify there's a ground wire wedged underneath one or the other. If the strings are not grounded, a loud buzz can definitely be an issue.

Another possibility is that the pickup and controls are not adequately shielded. There is likely a removable plate on the back of the instrument allowing access to the control cavity. The pickup will probably need removal to inspect the rout for the pickup cavity. Both need shielding to prevent 60-cycle hum.

This short tutorial from StewMac should help:

https://www.stewmac.com/How-To/Online_Resources/Learn_About_Guitar_Pickups_and_Electronics_and_Wiring/Guitar_Shielding.html

Jeff Highland · From: New South Wales, Australia

Could be a number of things,
Commonly
-unearthed strings/ bridge check with a multimeter for continuity between bridge and sleeve on output jack
-break in earth between instrument and mixer-are you using a ground lift switch on your DI
-unearthed mixer, is it connected to ground (3 prong chord/ outlet)
-Ground loop (using two or more connections to earth)

A mutimeter is your friend

Tim Jones · From: Oakland, CA

Great suggestions, thanks!

Whyyy does the power adapter for my mixer only have two prongs? That seems wrong!

Touching the strings or the output-jack reduces the hum somewhat, but not entirely.

OK this is gonna be complex. I will get out my multimeter, do some reading about how guitar grounding is supposed to work, and let y'all know how it goes.

Tim Jones · From: Oakland, CA

OK, I thiiink I've figured it out.

Problem#1 : My mixer is not grounded. I confirmed this is the major issue by running my guitar through the mic input in my DJ mixer, which is grounded. This connection had a lot lesss buzz.

Problem #2: My guitar's wiring is a bit bad. My multimeter shows no connection between the strings and the output jack. The level of buzz varies a lot depending which parts of the guitar I'm touching.

I'm not sure what the solution is, other than just giving up on my Behringer mixer. It's confusing that nobody else I can find with google has had this problem, considering what a popular line of mixers this is.

It's also confusing that the ground-lift in my fancy DI box did not help either of these problems. (OTOH this is a great excuse to return a $100 piece of gear, so I can't complain too much about it!)

Jeff Highland · From: New South Wales, Australia

I encountered this problem when using headphones on a multi-effects unit run on 9v dc
Despite my guitar being properly grounded and having a humbucking pickup I got a lot of hum because all the metal parts and sheilding on the guitar and the cable were not connected to mains ground so they still picked up noise and influenced the signal.
The solution for me was in one case to run a cable from the multi-effects unit to a plugged in but not turned on amplifier even when just using headphones On another rig I ran a ground cable from a mains plug.
The issue is that you have the guitar isolated from the ground so using the ground lift will not help
I could not find much about this situation online and not many people seem to understand it.
Mixers are intended for a balanced input from a microphone where this issue will not occur

Jim Kennedy · From: Brentwood California, USA

Be absolutely certain your bridge as a good ground. I have fixed a couple of older Fender P basses over the years with this problem. The grounding wire was simply laid between the body and the bridge. Over time the wire depressed into the wood and made poor contact with the bridge, causing the type of buzz you describe. Even if it looks good, make sure the ground wire and bridge are firmly connected. If the ground is poorly connected, the buzz will persist no matter what else you do.
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Jeff Highland · From: New South Wales, Australia

In this case, he may very well have a bad bridge ground, but the major problem is that the guitar is being fed into an unearthed mixer, with a ground lift switch in the DI breaking ground continuity as well.
With no continuity to Ground, noise picked up by the "grounded" components is just fed into the signal path.

Tim Jones · From: Oakland, CA

It's true, my guitar bridge does not have a good ground -- my multimeter shows no connectivity between the strings and the output jack.

I tried hacking a fix by running a wire from a screw in the bridge to a screw in the output jack. But now it has the weird effect of buzzing much less when I'm touching the strings than when I'm not -- which means the buzz is often strobing in and out as I play.

I could try using a normal guitar amp (with a headphone jack) instead of this mixer. Maybe that would fix it? Or maybe my guitar is just bad?

Jeff Highland · From: New South Wales, Australia

Ok you now have the strings connected to the sleeve connection at the output jack, the problem is that you have no connection from there to actual ground (mains ground)

When you touch the strings you are providing a ground connection through your body which reduces the buzz, the fact that this is occurring is a good thing.
Your guitar is not "just bad" it's now fine.

You just need to ground your mixer or something in the signal path before the mixer so that the ground is provided by another path than your body

If you want to keep using this mixer, perhaps get an electrician to make you up an earth cable from a mains plug to a small clip you can fix to the body of the plug going into the mixer.
Or go into a guitar amp with head phone outlet

Tim Jones · From: Oakland, CA

Argh - I'm now trying out the guitar with a small grounded practice amp. (An Orange Crush 12.)

It has the same buzzing problem that my Behringer mixer does.

Jeff Jim et al - big thanks for helping me think this through even though it is not going well.

Jeff Highland · From: New South Wales, Australia

Yet it's Ok into your DJ Mixer?
Are you just going Guitar- cable- Amp?

Tim Jones · From: Oakland, CA

Listening more closely...

When I plug it into the mic input of my DJ mixer, the hum is still present (and it's still affected when I touch the output jack). It's good enough that I can practice without being annoyed by it, but it's still bad enough that you couldn't make a professional recording with it.

With the amp - yes, I'm just hooking the guitar's output directly up to the amp with a cable. The hum is a lot louder than the DJ mixer setup.

Jeff Highland · From: New South Wales, Australia

Do you have another guitar you can try into the same setup for comparison?

Tim Jones · From: Oakland, CA

I do not -- but that seems like the right next step, so I will go find one. Smile

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