Hum when not touching the strings

[CoughSyrup]

I had a pretty horrendous hum from a set of GZR P pickups which was pretty infuriating given that split coils are not really supposed to hum and the installation is dead simple, so it would be hard for me to muck it up.

I finally caved and shielded it, including the underside of the pickguard and the hum completely disappeared.

 

[No Compute]

Have any science to back this up?

No. Human body an antennae for emf? Lol!!

I dunno, but Invalid Link Removed at the National Center for Biotechnology Information seem a little science-y to me. Then again, YMMV

 

[mngnt]

I dunno, but Invalid Link Removed at the National Center for Biotechnology Information seem a little science-y to me. Then again, YMMV

Very interesting.

Completely inapplicable to instruments and audible frequencies, but interesting.

 

[scuzzy]

I had a pretty horrendous hum from a set of GZR P pickups which was pretty infuriating given that split coils are not really supposed to hum and the installation is dead simple, so it would be hard for me to muck it up.

I finally caved and shielded it, including the underside of the pickguard and the hum completely disappeared.

It worked because shielding was the issue. Unfortunately people keep posting their opinions and muck up the entire conversation.

 

[MYLOWFREQ]

Do not stop playing.

 

[No Compute]

Completely inapplicable to instruments and audible frequencies, but interesting.

It is entirely applicable to any proximal un-shielded electronic network, including electric guitars and basses. And maybe even more important for the purposes of this discussion, an amplifier.

Why does an amplifier buzz loudly when you touch the tip of the input cable only? Because these stray frequencies being carried by your body are now being amplified. So they are definitely audible for an electric bass player’s intent and purpose, if not in the pedantic sense

 

[SulzerType2]

Have any science to back this up? A noisy bass will hum regardless of the proximity of a human. Please also explain why touching the bass elimates this supposed antenna effect.



I don't believe this is true. Try it and report back.

Edit: as I read your post again I don't even know where to start.

If your initial point is true, then all basses would exhibit this behaviour and would hum unless touched.

If your subsequent point is true, then fixing problematic ground connections would never solve hum problems.

There is undeniable evidence in this thread alone that shows that neither are true, so I have no idea what point you're trying to make.

 

[bigdaddybass12]

Don’t touch them !!
Too many dental x-rays?
Try standing on one foot.
Sorry, let me get back to the humor page!!

 

[mngnt]

It is entirely applicable to any proximal un-shielded electronic network, including electric guitars and basses. And maybe even more important for the purposes of this discussion, an amplifier.

Why does an amplifier buzz loudly when you touch the tip of the input cable only? Because these stray frequencies being carried by your body are now being amplified. So they are definitely audible for an electric bass player’s intent and purpose, if not in the pedantic sense

What you're describing is not what was tested in that study, where they tested signals in the millions of hertz (1Mhz - 90Mhz), finding that anything below 1Mhz was basically nil (instead of the ~0.00001% to 0.000000001 efficiency at 44Mhz), where both the transmitter and receiver are within a few cm of the player.

In addition, it is literally the opposite of the phenomenon described by the OP.

That said, funny enough if while touching the end of an amplified and unplugged jack as per your example, you were to ground yourself... Guess what would happen to the hum?? Spoiler: it goes away.

 

[No Compute]

if while touching the end of an amplified and unplugged jack as per your example, you were to ground yourself... Guess what would happen to the hum?? Spoiler: it goes away.

Excellent. So then you do understand the underlying concept at work here. I’m glad we both agree that the instrument (via the output jack, cable, the pedal chain, and ultimately the amplifier’s connection to a true Earth ground) is grounding the player and their accumulated stray frequencies once he or she touches the strings (as evidenced by your counter to my example). So do we also agree that the OP has both a valid ground and a need for some shielding?

Look, as it was said up-thread, this is a common question, and is comes up all the time. And I won’t call them out by name but I know of two professional EEs who have already replied here above. I mean no quarrel, but I am pretty certain they understand these concepts better than you and I do together on a scale of hundreds. So I will let their words speak for themselves.

I wish the OP luck in his or her journey to a quieter instrument, and I also wish you well until the next post we interact in. It is time for me to cook dinner and go to bed

 

[mngnt]

Excellent. So then you do understand the underlying concept at work here. I’m glad we both agree that the instrument (via the output jack, cable, the pedal chain, and ultimately the amplifier’s connection to a true Earth ground) is grounding the player and their accumulated stray frequencies once he or she touches the strings (as evidenced by your counter to my example). So do we also agree that the OP has both a valid ground and a need for some shielding?

Look, as it was said up-thread, this is a common question, and is comes up all the time. And I won’t call them out by name but I know of two professional EEs who have already replied here above. I mean no quarrel, but I am pretty certain they understand these concepts better than you and I do together on a scale of hundreds. So I will let their words speak for themselves.

I wish the OP luck in his or her journey to a quieter instrument, and I also wish you well until the next post we interact in. It is time for me to cook dinner and go to bed

I appreciate the reply, these conversations seem to typically degrade into adhominem ridiculousness.

Grounding is relative, so in the "touching an open jack" example, a larger ground (ie - true Earth ground) is needed to eliminate the hum introduced by our touch.

In OP's case, I believe that the human touching the bass becomes the ground. Touching the strings to a true earth ground with have the same effect.

Which is my theory. If the strings/bridge/bass/etc were properly grounded to begin with, it wouldn't be an issue. That the human touch makes a difference says it all. I don't believe it has anything to do with shielding.

I now understand the theory that the buzz comes from the human until they also ground themselves to a properly grounded bass... But I don't believe it is true. If it was, as said above, every bass would exhibit this behavior, especially those that are unshielded... But they don't. Further, resolving the problematic ground connection as mentioned by several people here, would also _not_ resolve the issue.

While I won't deny its theoretically possible, in that study they had to use very high freqs at very close distances to have the human body act in this manner. Since we know there are many cases of problematic ground connections (ie - why does the bridge ground exist at all?), it is a far more plausible cause, IMO.

Not to mention the fact that our body would need to significantly amplify the offending 60hz noise orders of magnitude above what the bass is already directly subject to. If we were a tuned antenna to 60Hz that's one thing... But we aren't, and we're comparing to a pickup literally designed to pickup signals in this frequency range.

A test would be to leave the OP's humming bass on a stand and walk away to see if there's an difference in hum based on their proximity to the bass.

 

[tb-player]

It's a ground issue. Play with a wireless. Breaks the connection.

I've been doing it for years and it works quite well.

 

[Goztheking]

If I am reading your post correctly, the hum goes away when you touch the strings?

If it is going away when you touch the strings, that doesn't sound like the usual 60 cycle hum from a single coil, that sounds like a bad ground from the bridge to the electronics. I recently had that issue after I rewired my bass kit build. I forgot to resolder the bridge wire to the rest of the ground circuit. The hum was there, but when I touched the strings, it went away (pickups are humbuckers). I realized immediately what my problem was, opened it back up, found the unsoldered bridge wire and soldered it where it belonged. Closed it all back up and the hum was gone.

Just my 2 pence.

In my experience, and that goes far enough for me to say really only that i've had this issue, not that i've fixed it (yet). I've had the same issue on all my guitars, (fender MIM, vintage fender MIA, Bc Rich MIA, rickenbacker, squier) as well as my amps, where it almost HAS to be dirty power or an ungrounded/bad breaker box right? hum whenever not playing, and mutes when i touch any metal part of my guiitars

 

[P. Aaron]

Band mates at a rehearsal one day were telling me my bass (Dimension) was humming. I told the guitar player (whose house we were at) to turn off the light dimmer switch in the room we were playing in. Hum gone.

They looked at me like I was a GOD.

 

[andare]

These threads always end up containing both right and wrong information.

Without getting technical, every guitar should have proper grounding and the cavities should be shielded and the shielding should be grounded.

Personally I haven't found the need to shield the pole pieces because they only make noise if you touch them and I don't play over the pickups.

If all of the above is done, the only noise you should hear is single coil hum, which can only be eliminated with another coil wired in reverse, be it a dummy coil or a second pickup.

So a P bass should be completely silent with both knobs at 10, no touching and standing in front of the amp. A Jazz bass too, with both pickups at the same volume.

An aluminum pickguard, which should be part of the shield, can actually make single coil hum quieter.

The quietest guitar I own is my Squier Precision Mini. All stock, the cavities are shielded with paint, the pickguard and pole pieces are not. Incidentally it's the loudest and fattest bass I have once I play it but standing in front of the amp without touching anything you would think it's broken.

 

[sunbeast]

I appreciate the reply, these conversations seem to typically degrade into adhominem ridiculousness.

Grounding is relative, so in the "touching an open jack" example, a larger ground (ie - true Earth ground) is needed to eliminate the hum introduced by our touch.

In OP's case, I believe that the human touching the bass becomes the ground. Touching the strings to a true earth ground with have the same effect.

Which is my theory. If the strings/bridge/bass/etc were properly grounded to begin with, it wouldn't be an issue. That the human touch makes a difference says it all. I don't believe it has anything to do with shielding.

I now understand the theory that the buzz comes from the human until they also ground themselves to a properly grounded bass... But I don't believe it is true. If it was, as said above, every bass would exhibit this behavior, especially those that are unshielded... But they don't. Further, resolving the problematic ground connection as mentioned by several people here, would also _not_ resolve the issue.

While I won't deny its theoretically possible, in that study they had to use very high freqs at very close distances to have the human body act in this manner. Since we know there are many cases of problematic ground connections (ie - why does the bridge ground exist at all?), it is a far more plausible cause, IMO.

Not to mention the fact that our body would need to significantly amplify the offending 60hz noise orders of magnitude above what the bass is already directly subject to. If we were a tuned antenna to 60Hz that's one thing... But we aren't, and we're comparing to a pickup literally designed to pickup signals in this frequency range.

A test would be to leave the OP's humming bass on a stand and walk away to see if there's an difference in hum based on their proximity to the bass.

A human body is not grounded under normal circumstances, and thankfully so or we’d be shocking ourselves constantly in a world full of appliances with different ground potentials and stray energy looking for different paths to ground.

The bridge ground on an instrument is indeed there to ground the body when touching strings. The body is essentially a big capacitor that picks up RFI noise, and when you ground yourself through the instrument you are basically turning your body into a big meat shield instead of a meat antenna. We aren’t the main pathway to lower frequency mains hum (60hz/120hz/etc), but contribute a lot to higher frequency noise that can be an issue regardless of using single-coils or humbuckers.

The reason not every instrument exhibits extreme noise issues when you aren’t touching the strings is that different instruments and different pickup designs have different shielding and otherwise different amounts of susceptibility to outside noise. A very well-shielded bass with proper grounding of said shielding will often show very little benefit to bridge grounding- in fact EMG recommends not using a bridge ground with their pickups as their design and internal shielding is so noise-resistant that it shouldn’t require the body to be grounded and having the body grounded can be dangerous (it’s how people get shocked through microphones, as there can be different ground potential between the PA and your guitar amp that causes stray charge to take the path through least resistance one way or another through your body to the guitar amp or PA amp ground connection).

A large number of factory basses are made with no shielding at all, so the OP’s issue is likely just a lack of shielding and the resultant need to ground his body through the bridge in order to decrease noise.

 

[mngnt]

A human body is not grounded under normal circumstances, and thankfully so or we’d be shocking ourselves constantly in a world full of appliances with different ground potentials and stray energy looking for different paths to ground.

The bridge ground on an instrument is indeed there to ground the body when touching strings. The body is essentially a big capacitor that picks up RFI noise, and when you ground yourself through the instrument you are basically turning your body into a big meat shield instead of a meat antenna. We aren’t the main pathway to lower frequency mains hum (60hz/120hz/etc), but contribute a lot to higher frequency noise that can be an issue regardless of using single-coils or humbuckers.

The reason not every instrument exhibits extreme noise issues when you aren’t touching the strings is that different instruments and different pickup designs have different shielding and otherwise different amounts of susceptibility to outside noise. A very well-shielded bass with proper grounding of said shielding will often show very little benefit to bridge grounding- in fact EMG recommends not using a bridge ground with their pickups as their design and internal shielding is so noise-resistant that it shouldn’t require the body to be grounded and having the body grounded can be dangerous (it’s how people get shocked through microphones, as there can be different ground potential between the PA and your guitar amp that causes stray charge to take the path through least resistance one way or another through your body to the guitar amp or PA amp ground connection).

A large number of factory basses are made with no shielding at all, so the OP’s issue is likely just a lack of shielding and the resultant need to ground his body through the bridge in order to decrease noise.

I'm not saying we're grounded, I'm saying our bodies provide a charge sink when touching something much smaller, relatively, like a guitar.

While I'm not saying what your suggesting isn't possible, the question remains why an unshielded bass is quiet at all when the strings are touched (certainly doesn't do anything for noisy Strats), and if our bodies do become a "meat shield", how it somehow manages to act as one in a 360deg sphere around the guitar. Such that the noise is completely gone.

Further, that our bodies apparently amplify this RFI from a distance? This behaviour would wreak havoc on sensitive electronics and humans would disrupt absolutely everything. I will also need some clarification on what an "RFI capacitor" is.

I have played a ton of instruments, many noisy, many not, and every case of noise change when touching the strings has been either bad ground or bad cable. Even my dollar-store Monoprice Strat didn't exhibit this behaviour.

 

[No Compute]

Horse?

Meet water…

Drink up, now

 

[Wfrance3]

Having a multimeter to test continuity of the grounding is incredibly helpful in these situations.

When I go to repair this kind of issue, I try to bring a gun to a knife fight. I completely foil tape the control and pickup cavity(s) of my bass with copper tape. Accept no substitutes. I've heard tell of people using aluminum tape and am glad that works, but copper has never let me down, so no reason to change my practice.
Next put your meter on tone and then randomly test points all over the cavity you are shielding. If you find a spot where you don't get tone, freeze. note the spots where your test probes are landed and then peel off a strip of copper and join the two spots. resume testing. keep going until you can go all over the cavity your are testing and get tone anywhere you check.
also, if you have a pick guard, shield that. Make sure there is a place where copper foil overlaps (at least) one of the screw locations where you screw down the pick guard. That way you have positive continuity between the cavity shielding and the shielding applied to to the pick guard.
Last trick I learned from Ibanez - run a wire from the bottom of the (each) pickup cavity to the inside of the cavity where the potentiometers live. Just bare the wire and screw it down to the floor of the cavity making sure you have good contact with the copper foil. Take the other end of that wire and solder it to the back of whatever pot your bridge wire is connected to.
All my basses are silent.