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I have a Fender Telecaster that hums loudly--much more so than other similar guitars. It's a standard Tele with single-coil pickups. The humming noise stops when the player touches the strings or other metal parts of the guitar. The guitar is plugged into a simple solid-state guitar amplifier. The humming noise sounds like 120Hz hum (see update below). I've tried plugging into a different outlet, turning off all the other electrical devices in the room including the lights, etc. Nothing helps.

I would like to understand:

  • What is causing the hum? I know it's "mains current" or something like that. I would like to understand what is actually happening.
  • Why does this guitar hum much louder than a Fender Stratocaster, which also has single-coil pickups?
  • Why does touching the strings cause the humming to stop?

The strings and other metal parts of the guitar are all connected to the jack and cable sleeve and all comprise the "ground" of the guitar-amplifier circuit. The cable sleeve is in turn connected to the metal amplifier chassis and ultimately to the mains ground.

I'm posting this question here because whenever I search for information about this on the web, I find all sorts of answers/explanations from people who don't know much about electronics that all contradict each other.

Some explanations I've heard:

  • "Ground loop." Ok, where's the loop? It's just a guitar plugged into an amplifier. This "explanation" is usually followed by advice to "break the loop," try removing/re-installing wires, use a ground-lifting cable or device, or something like that. How can I diagnose a ground loop like an engineer, maybe with a multimeter?

  • "Loose wire." The person providing this answer recommends checking solder connections etc. In the same thread, people have pointed to the fact that touching the strings eliminates the hum as both evidence of there being a wire loose ("your body completes the circuit!") and of there definitely not being a wire loose ("your body is being grounded through the guitar").

  • "Not enough shielding." Maybe? But why does touching the strings cause the humming to stop (after all the electronics are still unshielded right?) and couldn't we just do whatever touching the strings does, electrically, and thereby stop the humming?

  • "Your body is an antenna/capacitor plate." This explanation suggests the there is some potential being generated in the player's body that is being transferred to the pickup and that touching the strings grounds the player. This explanation seems promising but is always presented in a hand-wavy manner. Okay, so my body is an antenna, but why does that cause the guitar to hum, and why don't I cause other electronic devices to hum as I move around the room?

  • "Everyone knows Telecasters hum, just get used to it." I'm having trouble accepting that Fender would continue to produce a guitar that hums like mad when they obviously have the technology to mitigate the problem, as evidenced by the behavior of the Stratocaster in the exact same situation, in the same place, plugged into the same amp. I understand that single-coil pickups hum, but the Stratocaster hums like, well, every other Strat, while the Telecaster hum is obnoxiously loud.

The question was answered on Music: Practice & Theory Stack Exchange, but the answer there is typical of what I've found online. The answer is "grounding and shielding" and advises checking wires, changing components, etc. Someone brings up the "your body is an antenna" explanation in the comments. There's no explanation of what is actually going on.

I'm hoping that by posting this question in EESE, I can get a more satisfactory/scientific answer than the ones I've found so far.

Update to this question, 21-Sep-2019: I was able to do more investigation of this issue. I checked the grounding and confirmed that there is continuity all the way from the strings to the cable sleeve to the amp chassis and to the ground in the wall power socket. So whatever the problem is, it's not a missing or floating ground. Also, I took the guitar to a different location, with a different amplifier, and in that location, with that amp, the hum was greatly reduced and was more like typical single-coil pickup hum. I checked ground continuity in the new location, and it was fine. So it's some issue that is at least partially environmental (having to do with either the amplifier or the place) but only affects this guitar, or at least affects it more than it does other single-coil guitars like the Strat.

Another update: Actually the noise isn't a 60Hz hum; it sounds like the 120Hz "angry insect" hum that is often associated with ground loops. But I can't identify a ground loop here. The guitar is just plugged into one amplifier, which is plugged into one wall outlet.

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  • \$\begingroup\$ Does your amp or guitar have a toggle switch for phase or ground options? \$\endgroup\$ – Sparky256 Jul 20 at 0:30
  • \$\begingroup\$ The guitar is a Fender Telecaster so it's really basic. Just the usual 3-way pickup selector, volume, and tone. Schematic here: p4.zdassets.com/hc/theme_assets/549136/200076499/… \$\endgroup\$ – Willis Blackburn Jul 20 at 1:41
  • \$\begingroup\$ Try using a short insulated (so that your body doesn't affect it) wire connected to the jack sleeve and probe around the guitar to see if additional grounding helps. Touch the free end to the bridge and directly to the strings. I had an old bass guitar with similar problems but never really got to the bottom of it. \$\endgroup\$ – Transistor Jul 20 at 8:11
  • \$\begingroup\$ Two quick questions. (1) is the hum same for all 3 switch positions? (2) have you tried it outdoors? If yes, then any difference? \$\endgroup\$ – Kripacharya Jul 24 at 5:14
  • \$\begingroup\$ The hum is worse with the bridge pickup, which is interesting, because of course that's the pickup that was shielded by the bridge cover that Fender originally fitted to the guitar but that everyone took off and used as an ashtray. New Telecasters no longer come with the bridge cover. The neck pickup is "covered," in other words, it has a built-in metal shield. The pickup being an unshielded single-coil is definitely significant, but I don't have a scientific explanation for why touching the strings makes it go away. \$\endgroup\$ – Willis Blackburn Sep 21 at 20:19
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Normally severe hum means your strings and pickup coil are not grounded. There MUST be a short ground wire in the guitar that connects the body of the pickup coil and string clamp to signal ground. Normally the outer part of the 1/4" phono plug at the guitar is signal ground.

If this wire is missing or has come loose it must be repaired. Any color of stranded small gauge wire will do. I have seen and fixed this problem enough to say it is common with certain types of guitars and old hand-me-down guitars.

Take off the electronics cover plate and make sure this ground wire is present and is securely soldered at both ends. Also try other amplifier cables and wiggle the 1/4" plugs at the amp and guitar. If this creates a lot of noise and hum consider new cables, but check and/or fix the guitar ground first.

EDIT: Based on the diagram you provided the white wire from the Jack is signal ground, but the bridge plate part#21 should be connected to this white wire to ground the strings. Connecting the coils correctly does NOT ground the strings. Use a short piece of stranded wire to ground the bridge plate.

It would also be prudent to check this white wire from the Jack to make sure it has solid connections at both ends. If it comes loose the guitar will have no signal ground!

NOTE: Based on the diagrams there is no green ground wire from the pickup coil metal case and string bracket to the white signal ground. Add this wire and the hum should go away.

You should check for proper ground polarity at the amplifier. Some amps do have a ground polarity switch or ground phase control. Admittedly these controls are on expensive Peavy and other amps.

Seriously, your idea to try another amp points to your amp as being defective. Suggest you replace it with a better model if a service tech cannot find an obvious problem.

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  • 2
    \$\begingroup\$ This is the "loose wire" answer I mentioned in my question. How can the pickup coil not be grounded? The pickup only has two wires. If they both weren't attached to the right places, the guitar wouldn't work at all. Let's say you're right and there is no wire connecting the strings (really the bridge) to ground. In that case the strings aren't even part of the circuit so why would touching them do anything at all? \$\endgroup\$ – Willis Blackburn Jul 20 at 1:37
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    \$\begingroup\$ @WillisBlackburn Think about it. The human body has enough mass to act as a ground when touching ungrounded strings. If the strings are properly grounded there should be no hum whether the strings are touched or not. How does a guitar normally behave when strings are touched? By the way I was referring to the metal body of the pickup coil, not the signal wires. Not all guitars have proper grounds installed. \$\endgroup\$ – Sparky256 Jul 20 at 2:43
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The noise is catched by not so heavily shielded circuits. The amp input doesn't load it to its knees, because normally amp inputs are Hi Z to keep out the treble loss due the inductance of the mics. You become a part of the shielding when you touch the strings. They are internally connected to the signal ground. Test it. Try to replace yourself with a big piece of metal foil (as electrically).

ADD due the comments:

It's possible that the strings just in your Telecaster are NOT connected to the signal ground, so it differs from my Telecaster. There's a wire from the signal GND to the bridge and that way to the strings, too. It's shown also in available articles of Telecaster wiring.

But the strings are still connected to the other metal parts of the guitar except the signal circuit and you can be grounded via some other route, for ex you have leather shoes and you stand on concrete floor. Then you bring the needed grounding to the metal parts and the noise level drops radically

BTW. I assume the placement nor the position of the guitar need not to be changed, it's the touching only that's needed for the difference. Guitar placement dependent hum is picked by the pickup coils from surrounding magnetic fields - mains transformers in the equipment spread it. High impedance signal lines catch capacitively the electric field of the surrounding mains cables and lights. That is helped radically if the circuits are inside or even in the near proximity of a grounded shield.

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  • \$\begingroup\$ Doesn't your response contradict the one from @Sparky256? You're saying the strings are connected to the signal ground; he's saying they must not be connected to the signal ground. \$\endgroup\$ – Willis Blackburn Jul 20 at 1:30
  • \$\begingroup\$ @WillisBlackburn My answer clearly states that the strings and pickup coil MUST be connected to signal ground in the guitar or the result could be severe hum and noise. \$\endgroup\$ – Sparky256 Jul 20 at 1:35
  • \$\begingroup\$ @Sparky256 I understood you to be saying that the strings and pickup coil should be connected to ground, but that in the case of my guitar, they are not connected, and that is why my guitar is generating so much hum. So you said "your strings are not grounded." But user287001 is saying "your strings are grounded and that is why touching them silences the hum." Both explanations can't be correct. \$\endgroup\$ – Willis Blackburn Jul 20 at 1:54
  • \$\begingroup\$ Comment on your update: I don't know if the stings are connected to the signal ground or not. I'll check with a multimeter and see what's connected to what. \$\endgroup\$ – Willis Blackburn Jul 20 at 12:53
  • \$\begingroup\$ See the update that I added to the question. The Tele is correctly grounded. \$\endgroup\$ – Willis Blackburn Sep 21 at 19:55
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On reading your question, the replies and comments I do not see where you have definitively identified the source of the hum you are hearing.

There are two major ways the hum gets in to these circuits: conducted and radiated.

The source of conducted hum in electric guitars is often the amplifier.

The source of radiated hum in electric guitars is something in environment is generating a fairly powerful magnetic field. Often mains overhead power lines.

To test for a radiated source use a battery powered portable amp like a Pignose Legendary 7-100. Using an amp without any connection to mains will isolate the guitar from conducted hum. If you still hear hum go somewhere well away from any power lines.

In your case conducted hum could be easier to fix. The usual cause is poor quality soldering of the components in the guitar.

Next is failed capacitors in the pickup circuit. There are two possible circuits used in the Telecaster see these articles for good descriptions:

Factory Telecaster Wirings, Pt. 1

Factory Telecaster Wirings, Pt. 2

Note that there is usually a ground wire that connects the body of the tone and volume pots. Not every Telecaster seems to have this connection.

The least likely source of hum are bad pickups. These are all but impossible to repair but if you have disassembled your guitar this far you should check the solder connections of the hook up wire to the magnet wire on the pickups.

At this point is easier to just replace the pickups but then this is also a tricky process. This can involve putting shims under the bridge or neck pickups.

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  • \$\begingroup\$ Can you explain why the hum goes away when I touch the strings? \$\endgroup\$ – Willis Blackburn Sep 22 at 14:57
  • \$\begingroup\$ Note that in the USA 120 HZ harmonics are common. \$\endgroup\$ – Sparky256 Sep 23 at 1:07
  • \$\begingroup\$ The short answer is that touching the strings changes the impedance of the circuit that the amplifier sees and that new circuit attenuates the hum frequency more. \$\endgroup\$ – Dan1138 Sep 23 at 20:58
  • \$\begingroup\$ The long answer is a lot more complicated and requires more information from you to be able to ignore some of the more unlikely reasons. You have said that the hum frequency you hear is about 120 Hz. This suggests that you are in a country outside of the EU. It also suggests you are in a space with fluorescent tube lighting. Possibly a light industrial warehouse with dodgy electrics wiring. You have yet to add enough detailed observations to even begin to guess at the hum source. \$\endgroup\$ – Dan1138 Sep 23 at 21:01

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