Help me diagnose guitar hum/buzz

[condoravenue]

I have a new guitar (tele w/ noiseless pickups), and it is making a buzz or a hum noise. I run a cable directly from the guitar to Focusrite 2i2 audio interface, into a computer, through TV speakers. I don't have spare guitars, amps, or cables, so I don't know if the problem is in the audio interface, the cable, or the new guitar. But here is what I can tell you.

• I recognize the typical 60 cycle hum, and it sounds a lot like that.

• It hums regardless of which pickup is being used, but the tone of the hum changes.

• The hum is reduced, almost eliminated when I turn the guitar's tone knob to 0.

• The hum is slightly reduced when I touch the strings or other metal parts.

• The hum gets louder when i remove the cable from the guitar. Then it disappears if I remove the cable from the audio interface.

• The hum disappears when I turn the guitar's volume knob off.

• It makes the same hum in a laptop unplugged running on battery.

[olddawg]

I have a new guitar (tele w/ noiseless pickups), and it is making a buzz or a hum noise. I run a cable directly from the guitar to Focusrite 2i2 audio interface, into a computer, through TV speakers. I don't have spare guitars, amps, or cables, so I don't know if the problem is in the audio interface, the cable, or the new guitar. But here is what I can tell you.

• I recognize the typical 60 cycle hum, and it sounds a lot like that.

• It hums regardless of which pickup is being used, but the tone of the hum changes.

• The hum is reduced, almost eliminated when I turn the guitar's tone knob to 0.

• The hum is slightly reduced when I touch the strings or other metal parts.

• The hum gets louder when i remove the cable from the guitar. Then it disappears if I remove the cable from the audio interface.

• The hum disappears when I turn the guitar's volume knob off.

• It makes the same hum in a laptop unplugged running on battery.

Is the interface powered by usb or does it use an external power supply? I've had to use a ground lift adapter if the power supply is 3 wire AC plug to eliminate hum.

[condoravenue]

Is the interface powered by usb or does it use an external power supply? I've had to use a ground lift adapter if the power supply is 3 wire AC plug to eliminate hum.

It is powered by USB. The same hum occurs whether the usb audio interface is plugged in to a desktop or an unplugged laptop.

[dai h.]

hi,

are you possibly a beginner (or someone who doesn't have much experience with electric guitars)? It's quite normal for there to be a buzz when not touching the strings or other metal parts connected to ground. Usually, a guitarist keeps a hand on the strings, bridge, etc. to keep the buzz down (or quickly whips the volume control to zero). (If you didn't know) the direction you face with the pickups also has an effect on the hum and buzz (in a studio situation the guitarist might turn to find the orientation with least hum and buzz).

The hum gets louder when i remove the cable from the guitar. Then it disappears if I remove the cable from the audio interface.

this is entirely normal as well. The non-terminated input (the super high impedance the input is now seeing now that the guitar's pickup and internal circuitry isn't across the tip and ground of the plug) plus the length of the guitar cable makes a good antenna to pick up noise.

(If the guitar's internal cavities aren't presently shielded already) applying shielding (copper foil, shielding paint, etc.) should help somewhat with the buzz (the harmonics of the hum which are probably more problematic since more noticable and annoying). To counter the hum, you might look into a humbucking coil.

Is the interface powered by usb or does it use an external power supply? I've had to use a ground lift adapter if the power supply is 3 wire AC plug to eliminate hum.

Lifting safety grounds are generally not recommended (and probably illegal). Hum can be very annoying but you do want to solve hum/buzz problems in a safe manner.

[condoravenue]

I played the same American Deluxe version Strat (and others) for a long time. I'm sure the buzz isn't from me not pressing hard enough or in the wrong spot or something. When playing the guitar, like you said I keep all the strings I'm not using muted to prevent them from sounding or to prevent feedback. Touching the strings doesn't stop the noise, just reduces it by about 40%.

Also, since my guitar came with stock N3 noiseless pickups (similar to the ones in my previous strat), shouldn't there not be a 60 cycle hum? Even when I press the s1 switch to use both pickups in series the same hum is present.

[dai h.]

is the interface this one?

Scarlett 2i2 | Focusrite

http://d3se566zfvnmhf.cloudfront.net...r-guide-v2.pdf

(a video of one supposedly being used--doesn't sound particularly noisy to my ear) :

https://www.youtube.com/watch?v=B-_r_NDdhR4

I suppose the "noiseless pickups" should have lower noise than usual but not eliminate noise entirely. (Probably depend on things like gain (more gain = more noise), how close (or far away) you are to noise sources.)

Have you tried moving the orientation of the guitar to check if a nearby noise source is getting into the pickups? Maybe try adjusting the gain (possibly too high?)? Make sure the guitar cable's contacts (plugs) are clean (and the input end on the interface as well). (Maybe not likely but) check that you're not unknowingly using a speaker cable.

[condoravenue]

Ok. I tried it back in my laptop, and unplugged the laptop, and as I distanced the laptop from other electronic items, the hum disappeard 100%. I also discovered when the computer is plugged in and the hum is sounding, the guitar (and computer) will slightly shock me if I touch the metal parts. I live in India, where electronics aren't grounded well. Do you have any suggestions on how I might be able to run my guitar through the desktop and eliminate this hum?

[dai h.]

Are all the AC outlets 2-prong with no 3rd prong (safety ground)?

How do you get shocked (i.e. are you getting shocked when you are holding the guitar and then touch something else? Or, just simply touching the guitar?)?

[condoravenue]

All the outlets in my apartment are 3 prong outlets. I suspect the grounding isn't correct though. It is a very light shock that occurs when I am standing and touch the tuners, the strings, the bridge, or even my computer. Holding the guitar or leaving it on the stand didn't make a difference. Remember the shocking and the humming go away when I remove the power adapter and run on battery backup.

[Tom Phillips]

You have provided several good bits of troubleshooting information.

...The hum disappears when I turn the guitar's volume knob off...

This shows that the hum is being caused by electromagnetic energy in the room being picked up by the guitar’s pickups and wiring. Every wire carrying current and every electrical device in the area can generate electromagnetic energy. Additional clues are discussed below.

Ok. I tried it back in my laptop, and unplugged the laptop, and as I distanced the laptop from other electronic items, the hum disappeard 100%...

By “...distanced the laptop from other electronic items...” does that also include the guitar itself? This indicates that the primary offending electromagnetic field is being generated by one or more of you electronic items. The good thing here is that you have found an equipment placement that eliminates the hum. You can experiment further and may find an equipment placement that has acceptably low hum even with the laptop plugged into the charger. You can investigate by spreading out the equipment and then using your guitar as a sniffer by moving it around and near the equipment to determine which item(s) are radiating the hum causing field. Then you can decide where best to place each piece of equipment for lowest hum.

...the shocking and the humming go away when I remove the power adapter and run on battery backup.

The shocking issue is the most critical problem to fix. It indicates that something is wrong with the overall safety grounding system AND that there is indeed a ground path through your body. That body ground path can be obvious such as you touching a grounded metal object or more subtle such as through your shoes to the floor and on to earth ground. Your best approach is to find and repair the faulty safety ground.

[dai h.]

if the notebook power supply and desktop power supply and powered speakers' power supply are all 3-prong and have the 3rd safety ground prong/lug connected, I don't think you should be getting shocked just standing and touching something (like Tom says, there seems to be current flowing), so that isn't a very good situation.

An easy way to measure a voltage difference between your body and metal parts that can be touched is to get a DVM(digital volt meter), then (on the AC volts reading setting) hold one lead while touching the other lead to metal parts that you can touch (metal guitar cord lead covers, and anything else you can come into contact with--they are usually connected to circuit ground). (Looking at such reading) if you see something high (tens of AC volts or higher), you can be shocked.

Basically you want all parts a human can touch to be the same potential (no difference in voltage) as well as having no (or very little) difference between the physical ground(floor, etc.) that you are standing on. Worst case scenario (from what I understand) is a shock through the heart which stops the heart and no spontaneous recovery, and no one is there to get medical attention (and "lights out" permanently).

[Mick Bailey]

Switched mode power supplies often connect the primary to the secondary via a capacitor intended to reduce EMI. The results in a relatively high voltage appearing on the output of the supply. Most consumer audio equipment powered this way no longer relies upon a ground connection and even if a three-prong socket is present often there's no connection inside the unit.

The result is around 80v or so appearing on the output of the supply, both on the ground and 'hot' connections.

Now, lets say you plug your guitar into a pedal board, but don't connect it to the amp (yet), and that pedal board has a switched-mode supply (SMPS). This is now the most common form of supply. All of the metalwork will 'float' at 80v relative to ground, including your guitar. Some people are more sensitive to this and will feel a tingling or shock sensation when touching the guitar or any of the pedals. Now you plug the pedal board into the amp. Most guitar amps have a three prong grounded connection, and this is also connected at some point to the signal ground. This then shunts the 80v to ground and because it's at relatively high impedance the voltage disappears and there's no further tingle or shock from the guitar.

With your setup you need to check if the power supplies use a 2-prong connection at the power supply end. Often this will be a 'figure of 8' connection. If all your equipment is powered this way then there's no ground path for the 80v or whatever, other than your own body.

A quick search for 'laptop shocks' will show this is a common problem.

The main concern is differentiating between a fault and expected behaviour, so the first thing to check is the PSU connection type.

[condoravenue]

I found a place where I could check a few things through an amplifier in a different building. I used another guitar and another guitar cable. My guitar and cable are fine. Regardless of proximity to other electronic equipment, if the computer is plugged into the wall (back in my apartment), the hum is very loud. It's quieter when I touch the strings, but still very loud and annoying. Note that the same hum sound comes from my laptop's internal speakers, and my desktop's internal speakers; I'm not using external powered speakers. Also note I don't use a pedal board, or a guitar amplifier. Guitar -> Audio Interface -> Computer (Amplitube). Someone told me the problem is that my apartment isn't grounded properly. Could that be right? Is it possible that putting an Ebtech Hum Eliminater (Ebtech 2-Channel Hum Eliminator | Musician's Friend) between my guitar and audio interface would fix this?

[eschertron]

I haven't seen where you say that the laptop's power supply is 2-prong or 3-prong. With the setup you describe, and a 2-prong plug on the laptop, you may have no ground reference at all. Can you ground the audio interface by running to the ground tab on a 3-prong adapter (adapter plugged into the wall, nothing needs to be plugged into the adapter)? Is there a point on the interface that is is identified as a ground (screw, tab, etc)?

I'm also confused by the info about distance and hum reduction. You said you found a point where the hum was eliminated 100%. Was this not a workable solution?

[Mick Bailey]

I'm not using external powered speakers. Also note I don't use a pedal board, or a guitar amplifier. Guitar -> Audio Interface -> Computer (Amplitube).

I understand. I was using the guitar/amp example to illustrate how the voltage gets shunted in a setup where a ground is present. Regardless of what your mains plug looks like, if the connection to all the PSUs is 2 pin you may have no ground path in your setup. I sometimes come across this and have a separate reference ground connection (a three pin mains plug with only the ground connected and not switched on) that has a croc clip attached. This is useful to diagnose situations like this where there's a shock sensation from the guitar in an ungrounded SMPS environment.

Hum and noise radiated from computers into guitar pickups is difficult to resolve. Just like playing a guitar too close to an amp. You have to move further away and often no amount of shielding or grounding will resolve it. Because the hum goes away when you turn the guitar's volume down, then the pickups are just picking up any radiated electromagnetic field. Most hum eliminators consist of isolation transformers to break ground-loop hum and can't eliminate the noise induced into pickups from other sources. Maybe an experimental ground as per eschertron's suggestion may reduce the hum.