Annoying Hum (Not a "ground loop")

[Ted]

Here in Madagascar, it's very common that houses are built without grounding in the electrical sockets – and that is my situation. (So ground loop suggestions do not apply here.)

I need suggestions for how to eliminate an annoying hum that I get when I record – particularly instruments with piezo pickups. My guitars with regular coil pickups don't have a problem.


The Hum Before the Recording Interface (Micro BR)

I've been looking into this for awhile now. The hum is about 20 cents above the low G on a bass.

 

Using Audacity I can use a notch filter to suppress that.

But, crap, this takes away the spontaneous fun of recording. I don't want to export every piezo-recorded track to a WAV for processing, and then import it again into my Micro BR or GarageBand.

And I don't necessarily want to always record on 100 percent battery power – Micro BR and the whole effects chain.

I experimented with a line conditioner today (borrowed from my refrigerator), and that helped only a little.

Do these things actually work? I could probably find these locally.

I've also looked into noise reducer pedals, such as the Boss NS-1. But that's expensive and would be a hassle to get to Madagascar. I haven't ruled it out, though.

The Hum in the Power

Plus there's a infrasonic hum I've I discovered when I was testing my micro-Thumpinator. I determined that this comes from the dirty power in Madagascar. Nothing I do in the signal chain between the guitar and the Micro BR will help this. (Maybe with the power conditioner. I didn't test that scenario for infrasonics.)

I can use a high-pass filter in Audacity to get rid of those infrasonics. This is less of a problem, because it's just one more final step after mastering, and before exporting the final WAV or MP3. (i.e. Unlike the 51Hz hum mentioned above, I don't have to add steps to recording each track to run the notch filter.)

Jumper Cable

When I touch the metal barrel of the guitar cable with my fingers, the hum disappears completely. So a ridiculous solution I'm thinking of trying – because I know it will work – is to create something like a jumper cable: clip one end to the barrel, and the other end to myself somewhere – an armband, or something with skin contact. (I said it was ridiculous.)

I'm hoping you folks have better suggestions.

[Farrell Jackson]

Hi Ted, a while back I posted in the gear lust forum about a Noise Decimator pedal that I purchased. It might be something that could solve your noise problems. Here's the link: https://songcrafters.org/forum/index.php?topic=31830.0

Farrell

[Ted]

Hi Ted, a while back I posted in the gear lust forum about a Noise Decimator pedal that I purchased. It might be something that could solve your noise problems. Here's the link: https://songcrafters.org/forum/index.php?topic=31830.0

Thanks! I'll keep that in mind. Ordering things online and getting them shipped here is really a problem. My last two experiences getting things through customs were nightmares. So a pedal is the last resort, but it's good to have a recommendation.

[Ted]

Today I bought a power conditioner at a local hardware store. And then I did a bunch of tests in 10 different scenarios.

Oddly, the infrasonic sound was not present in any of the tests – even where the conditions were seemingly identical to the conditions where the sound showed up (i.e. without the power conditioner, piezo pickup, etc.). So those sounds must be generated by something that goes on in my house, or my neighborhood intermittently. We'll see if they show up again. If they never show up again, I can probably thank the power conditioner.

The single most effective thing I tried was the "Jumper Cable" experiment. I bought a couple of alligator clips, and ran a wire from the barrel of my guitar cable to the waistband of my pants where the clip was in contact with one of my love handles (not my little finger, as pictured here).

[Zoltan]

I bought a couple of alligator clips, and ran a wire from the barrel of my guitar cable to the waistband of my pants where the clip was in contact with one of my love handles

This gives a totally new meaning to the saying that someone is really connected to his/her music.

[64Guitars]

The single most effective thing I tried was the "Jumper Cable" experiment. I bought a couple of alligator clips, and ran a wire from the barrel of my guitar cable to the waistband of my pants where the clip was in contact with one of my love handles (not my little finger, as pictured here).

If touching the barrel of the guitar plug reduces the hum but touching the strings, bridge or tailpiece does not, then the guitar probably has a grounding problem. An electric guitar normally has a wire soldered to the bridge or the tailpiece which is connected to the guitar's grounding circuit. Therefore, when you touch the bridge, strings, or tailpiece, it is electrically equivalent to touching the guitar plug's barrel since the grounding circuit connects them.

As a test, run your jumper wire from the guitar plug barrel to the tailpiece or bridge. If that eliminates the hum to the same degree as touching the guitar plug barrel, then it would probably be a good idea to open up your guitar and check the grounding circuit. Perhaps the internal wire going to the bridge or tailpiece has come off and needs to be re-soldered.

By the way, an improperly wired guitar can have ground loops within it. For instance, if you have 4 pots (2 volume, 2 tone) and their metal bodies are all wired to each other (pot 1 to 2 to 3 to 4 and back to 1), then that forms a ground loop. The correct way to do it is to have the ground wire go to pot 1, then to pot 2, then to pot 3, and then to pot 4, but not from pot 4 to pot 1.

See some of the many pages on electric guitar grounding for more info.

[AndyR]

The single most effective thing I tried was the "Jumper Cable" experiment. I bought a couple of alligator clips, and ran a wire from the barrel of my guitar cable to the waistband of my pants where the clip was in contact with one of my love handles (not my little finger, as pictured here).

If touching the barrel of the guitar plug reduces the hum but touching the strings, bridge or tailpiece does not, then the guitar probably has a grounding problem. An electric guitar normally has a wire soldered to the bridge or the tailpiece which is connected to the guitar's grounding circuit. Therefore, when you touch the bridge, strings, or tailpiece, it is electrically equivalent to touching the guitar plug's barrel since the grounding circuit connects them.

As a test, run your jumper wire from the guitar plug barrel to the tailpiece or bridge. If that eliminates the hum to the same degree as touching the guitar plug barrel, then it would probably be a good idea to open up your guitar and check the grounding circuit. Perhaps the internal wire going to the bridge or tailpiece has come off and needs to be re-soldered.

By the way, an improperly wired guitar can have ground loops within it. For instance, if you have 4 pots (2 volume, 2 tone) and their metal bodies are all wired to each other (pot 1 to 2 to 3 to 4 and back to 1), then that forms a ground loop. The correct way to do it is to have the ground wire go to pot 1, then to pot 2, then to pot 3, and then to pot 4, but not from pot 4 to pot 1.

See some of the many pages on electric guitar grounding for more info.

+1 to all this.

When I read the "touching the barrel of the jack" I thought exactly the same thing. But I was too tired and emotional (drunk!) to type coherently. I came back to put an answer of some sort in while the sunday lunch is cooking and the next bottle of wine is attaining room temperature and...

... 64G has saved me the trouble

[Ted]

If touching the barrel of the guitar plug reduces the hum but touching the strings, bridge or tailpiece does not, then the guitar probably has a grounding problem.

Admittedly, I don't know much about grounding issues. But my outlets aren't grounded.

It's only the guitars with piezo pickups – where the strings don't contact a metal bridge – that produce the hum. Some worse than others. So it makes sense that my guitars with regular coil pickups – which also have metal strings and metal bridges – are the ones that don't produce a hum. My Strat produces just a little bit of hum if I'm not touching the strings. My Yamaha electric bass doesn't hum at all, regardless if whether I am touching the strings or a metal component. It would seem like a big coincidence that all of my piezo pickup guitars have wiring/grounding problems. (I have 5, if you count the two kabosies)

[64Guitars]

Admittedly, I don't know much about grounding issues.

I'm no expert on grounding either, or electrical power systems for that matter. So don't take everything I say as fact. I could be wrong. Having said that ...

But my outlets aren't grounded.

I assume you mean that the electrical outlets have only two wires; hot and neutral. They lack a third wire for ground. From what I've read, I believe that two-wire electrical power systems have the neutral side connected to ground at the main electrical panel or at the street transformer. So, even though your outlets don't have a separate ground wire, they are grounded. That's why the hum goes away when you touch the plug on your guitar cable. The guitar cable's outer conductor (shield) is connected to the amplifier's signal ground circuit which is ultimately connected to ground through the amp's power supply via the neutral side of the electrical outlet.

I believe that the separate ground wire in three-wire electrical wiring is there for safety, not to make your guitar sound better.   So you should be able to have hum-free sound even though your electrical wiring is only two-wire since it's grounded through the neutral side of the electrical wiring.

It's only the guitars with piezo pickups – where the strings don't contact a metal bridge – that produce the hum. Some worse than others. So it makes sense that my guitars with regular coil pickups – which also have metal strings and metal bridges – are the ones that don't produce a hum. My Strat produces just a little bit of hum if I'm not touching the strings. My Yamaha electric bass doesn't hum at all, regardless if whether I am touching the strings or a metal component. It would seem like a big coincidence that all of my piezo pickup guitars have wiring/grounding problems. (I have 5, if you count the two kabosies)

Admittedly, it is strange that all of the piezo-equipped guitars have the same problem. So it's probably not a fault in the wiring of the guitars. However, it's a fact that touching the plug on the guitar cable reduces or eliminates the hum. So it follows that if you can connect the strings to that same ground point, the hum will be reduced or eliminated whenever you're touching the strings, which is nearly all the time when you're playing. If your bridge is not metal, then you should look for another way to ground the strings. If any of the guitars have a metal tailpiece or bridge plate where the ball end of the strings rest, you could connect a ground wire to that. If not, you could consider installing a PlateMate. Not only will it provide a way to ground your strings, but it will also protect the wood of your guitar from being damaged by the pressure of the strings digging into it.

Piezo pickups are quite sensitive and the signal level produced is quite low, which is why they need a preamp in the guitar. That might explain why you only have the hum with your piezo-equipped guitars. Relative to the weak signal from the piezo transducer, the level of the hum is high. Then both the signal and the hum are amplified by the preamp. Magnetic pickups have a stronger output so they don't need a preamp in the guitar and any hum that might be present is quite low in level relative to the strong signal level from the magnetic pickup. So you don't notice any hum.

This page might be helpful, especially the section under the heading "Stopping Takamine Bone Saddle Hum".

[Ted]

I assume you mean that the electrical outlets have only two wires; hot and neutral. They lack a third wire for ground. From what I've read, I believe that two-wire electrical power systems have the neutral side connected to ground at the main electrical panel or at the street transformer.

That's correct. Even when the outlets have the ground pole, there's no wire behind it. They are French-style outlets like this:

Thanks for the links. Very useful. As I said, it's really difficult to get things shipped here to Madagascar. (Technically, not that difficult. But it takes weeks and sometimes shipments get flagged by Customs, and the customs duties are exorbitant.)

I know a luthier here. He did some work on my kabosies, and built one of them. I bet it would be easier for him to create a "plate mate" than for me to order one. And he could maybe make a custom version for my kabosy with the piezo pickup.

My noisiest instrument is my Michael Kelly acoustic bass. I don't remember for sure, but I may have had a local luthier in the US put in a bone bridge after I bought it. (This guy supposedly was a top-notch luthier, so presumably he would have known if a bone bridge would result in noisiness.) It's possible that the bridge and pickup in the Michael Kelly bass has issues similar to the Takamine.

The thing is, I've recorded with this Michael Kelly bass quite a bit – including here in Madagascar, in a different house – and I never noticed the hum issue until now. So I have to wonder if there is some electrical interference in the house where I live.

I can do a little forensic research: Look for my old raw files from previous recordings with this bass, and see if that hum is present in recordings I made where I used to live. The harder part will be remembering whether I recorded with the Micro BR on battery power or plugged in.