Disagreement with my tech : is humbucker grounding needed?

[pyrroz]

Hello again,

this is old time classic old-school question like 2011 rewind (ohhh the nostalgia!) :

This is my tech, I have trusted him for 3 major repairs and I think he is as good as Cyn1 : manmadeguitar.com/

Yesterday for no reason, (yes in Athens you have to have a reason) I paid the tech a visit to his shop, as I was around the block spying on my Son and his behavior (long story).

The tech's work is perfect, however we got into a debate . He claims that humbuckers dont need no bridge grounding. When he did my Carvin, transformation from left --> right and he did an absolutely fantastic job beyond belief, he didn't ground the bridge. The guitar has HSS : dimarzio super-distortion bridge/generic carvin middle/air norton S neck. I realized this right away. My rig basically consists of :

guitar --> boss me-25 --> headphones, so this was pretty audible. I tried with other DMZ guitars I have and they were dead silent.

So I conencted the bridge ground and I noticed that :

a) when playing via the me-25 with the amp unplugged the noise was there : not hum, more like a high freq bzzzz / hiss

b) when playing via the me-25 with the amp plugged (regardless of the amp being on) the noise was gone

I know there have been ages since I moded any guitar, but according to the theory should HB also cancel high freq hiss besides regular hum? Why does grounding the bridge actually works?

Again sorry for forgetting all the old classic original GN theory ... I am getting old, can you pls shed some light to this question?

[newey]

pyrroz-

Hello again!

HBs are designed to reduce hum being picked up from the pickup windings. The string/bridge ground is there for a different reason- to ground out noise coming from your body. So, it's "apples and oranges", as we say.

Now, strictly speaking, string/bridge grounds are not absolutely needed. Many of those big "jazz box" style of guitars had (and still do have) no bridge/string ground. But when those things were first designed, there was no such thing as "high gain" amplification or distortion boxes, etc. In most playing environments, the jazz boxes were quiet enough without string grounds.

But then, amplifiers got more powerful, and people started playing with gain, distortion etc.- and string/bridge grounds helped reduce noise to some extent.

Many manufacturers make HB-equipped guitars, and I've never seen a manufacturer's factory wiring diagram that didn't include a string/bridge ground. While the cost of wire is not much, when one makes thousands of guitars it adds up. Also, there is additional woodworking, to drill a hole for the string ground wire to run to the control cavity, this adds an extra machining step that manufacturers would love to avoid if they thought they could do so. So, when your tech says it's not needed with HB-equipped guitars, you should ask why, then, do all the manufacturers spend the time and money to put that wire in there? Maybe the manufacturers know something about this?

As to your particular noise issues, I have no idea why there's a difference, other than to say that, even with the amp off, the cord is still connected to the ground side, so maybe that makes the difference.

[pyrroz]

thnxxx

connecting to the amp definitely makes a difference!

[unreg]

Dec 21, 2020 8:16:19 GMT -5 newey said:

Also, there is additional woodworking, to drill a hole for the string ground wire to run to the control cavity, this adds an extra machining step that manufacturers would love to avoid if they thought they could do so.

A new hole is needed for bridge ground wire? I just ran that wire through the hole for the humb cables; though, had to make the hole a bit wider on one end by chiseling with a small flat head.

Does that ground wire along side the signal wires cause buzz? I felt that was ok to do since lots of the cables have braided grounds around signal wires.

[newey]

Dec 21, 2020 12:07:18 GMT -5 unreg said:

A new hole is needed for bridge ground wire?

Depends on the type of guitar and the cavity routing, but usually, yes it is. Certainly on Strat-type guitars, there is a tiny hole drilled between the trem cavity and the control cavity for the string ground wire to go through.

Does that ground wire along side the signal wires cause buzz?

Shouldn't be an issue.

[unreg]

Thank you sir newey! 👍😀

[pyrroz]

hi ppl, we had gone through all those 10 years ago back in the good old GN2, but still newey I am puzzled :

I did the test with full high gain, and I disconnected the plug from the amp, then the noise when away when I touched the strings (gosh do I hate sounding like a 15 yr old noob). So maybe human body somehow acts as a ground drain?

(again I know we have been to it ages ago and for ages and ages I am unacceptable forgetting basic truths of life!)

[unreg]

pyrroz, I’m going through the same learning... Your body does work as a ground drain. You could try moving your amp to another outlet/electrical circuit bc your guitar may be receiving electrical interference. I did this and noticed that sometimes, now after all of my guitar electronics editing, in other rooms the buzz completely vanishes; this seemed insane bc I was at the same different electrical outlet... had just moved a bit around.

Not to a new location, but enough movement so the cable moved a bit.

Then, remembering a suggestion to try different cable/amp came to mind! And so I’ve bought a new 10’ Ernie Ball braided cable. This cable is of good quality and should probably be much better than the free Mars Music cable that came with my guitar. Hope this will silence the buzz when it arrives.

[pyrroz]

Dec 21, 2020 13:17:02 GMT -5 unreg said:

pyrroz, I’m going through the same learning... Your body does work as a ground drain. You could try moving your amp to another outlet/electrical circuit bc your guitar may be receiving electrical interference. I did this and noticed that sometimes, now after all of my guitar electronics editing, in other rooms the buzz completely vanishes; this seemed insane bc I was at the same different electrical outlet... had just moved a bit around.

Not to a new location, but enough movement so the cable moved a bit.

Then, remembering a suggestion to try different cable/amp came to mind! And so I’ve bought a new 10’ Ernie Ball braided cable. This cable is of good quality and should probably be much better than the free Mars Music cable that came with my guitar. Hope this will silence the buzz when it arrives.

thanx man!

[newey]

Dec 21, 2020 12:54:49 GMT -5 pyrroz said:

So maybe human body somehow acts as a ground drain?

Your body does work as a ground drain

No, exactly the opposite. First of all the term "ground drain" is misleading; analogizing electrical currents to flowing water is only a somewhat useful analogy. Current doesn't actually get "drained" to ground in any meaningful sense. Ground is just one side of a circuit, and in an AC circuit like your guitar, it's not even a fixed side

But more basically, it is not that your body is "draining" any noise- your body is the source of the noise. While our pickups can pick up noise from a number of sources, one big one is the human body,

If your guitar becomes quieter when you touch the strings, it means your string ground is working as it should- noise being produced by your body is being grounded through the strings, through the string/bridge ground wire, and thence through the guitar cable to the amp ground, and to the electrical circuit ground for your household mains current.

(for the record, I didn't understand this until, years ago, ashcatlt explained it to me, so the thanks here should go to him- as he is fond of saying, your body is just a "big bucket of noise")

[unreg]

Dec 21, 2020 16:07:25 GMT -5 newey said:

If your guitar becomes quieter when you touch the strings, it means your string ground is working as it should- noise being produced by your body is being grounded through the strings, through the string/bridge ground wire, and thence through the guitar cable to the amp ground, and to the electrical circuit ground for your household mains current.

(for the record, I didn't understand this until, years ago, ashcatlt explained it to me, so the thanks here should go to him- as he is fond of saying, your body is just a "big bucket of noise")

Sigh, I’m sorry for misleading you pyrroz. Ok, so our bodies are the source of noise... and when we ground our bodies that noise disappears. Now, that makes perfect sense newey! Thank you so much ashcatlt! 😀

So, would a new cable not affect that noise? I guess, all of the bridge grounding and cavity wall grounding completely solves that noise problem.

Hmmm, but if the guitar still gets quiet after touching its strings, that problem mustn’t be solved yet?

Ahh, but that quieting with my fingers just happens near the electrical interference... though, at another outlet/electrical circuit, I believe I can still quiet the sometimes-buzz by touching the strings if it is present... so I’m a bit confused.

Oooh, so maybe my (low quality?) cable is picking up the noise from my body... and that noise wasn’t present when standing away from the cable in a location free from electrical interference. Think I understand now.


And the star ground paperclip that avoids the new pots’ cases solves another noise problem.

So, for my situation, the new cable may solve the remaining problem? (Hopefully. 🙂)

[pyrroz]

shouldn't the humbucker principal of operation also apply in the case of human noise as in the case of 60Hz EMI and also radio RFI noise?

[newey]

A HB is going to generally be quieter than a single coil, but hum-cancellation is not perfect.

Back in the early days of the Board here (I won't even try to guess where the thread might be), we had someone do some empirical testing. He was experimenting with playing while having a metal (steel) ring slipped around one of his right-hand fingers; a wire was attached to the ring and the other end was connected to a metal heat register in his home (i.e.,to a part of an all-metal HVAC system which was, in turn, grounded). This effectively grounded his body.

The idea was that this would lessen the noise not only while he was touching the strings while playing, but also when not touching the strings. He claimed that this worked, the noise was reduced even when not touching the strings. Ideally, a test would have included also doing this with the string/bridge ground disconnected, but IIRC he didn't do that.

We can also think about this the other way. If the idea was correct that the body was "draining" noise to ground,then we would expect a difference depending upon the grounding of the body. If, for example, someone were wearing rubber-soled sneakers, we should expect touching the strings to cause very little if any reduction, whereas someone standing in barefeet on a wet concrete floor (do NOT do this at home with a plugged-in guitar in your hands!) would have greater reduction. But this doesn't occur, we observe that touching the strings reduces the noise uniformly regardless of shoe type, etc.

[ashcatlt]

If newey got it from me, it was only because I was repeating what somebody else around here had explained previously.

But yeah, if you happen to have a pickup whose pole pieces are not themselves grounded, and you manage to touch one of those pole pieces without also touching the strings, you should notice that the noise gets significantly louder. The noise from your body is being focused right in the middle of the coils where it can be most easily transduced. Our bodies do generate their own noise (you are an electrochemical machine), but also tend to somehow collect and focus the EM/RFI noise in the world around us.

Humbuckers work via phase cancellation and that depends on a strong correlation between the two signals. For perfect cancellation, they need to exactly the same amplitude and exactly in phase which is to say time aligned. If the two coils of the humbucker were exactly the same and in exactly the same place, they would pickup every noise source exactly the same and cancel perfectly. But of course they aren’t and can’t be, so they don’t. Any given source is going to be louder in one or a little earlier or both. When it comes to time alignment, lower frequencies are “more forgiving” in that you can have longer delays between the two signals and still get at least some cancellation. I think that’s maybe why humbuckers tend to buck hum (lower frequency noise) better than hiss (higher frequency noise). What I tend to call buzz is actually distorted hum - some low fundamental noise with harmonics that extend into the higher frequencies - and sometimes a guitar will do a great job of cancelling out the lower frequencies but you can still hear those annoying high harmonics.

Shielding and string ground I think work somewhat differently. There’s kind of two ways to look at it, and I actually think both are true to some extent, but neither actually have to do with anything being drained away. It’s all about completing a circuit.

One way I’ve seen it explained is to imagine something like a radio antenna. One end is connected to the actual earth, and the other end is up in the air. The signal is capacitively coupled to your guitar and wants to complete its circuit back to the antenna. It can get there through the hot wire of the guitar, but that is a high impedance path, and if it can get there via a a lower impedance path like the ground wire, it would “prefer” to do so. If the ground path is actually 0 ohms all the way back to the antenna, then the noise source is essentially shorted before it can get to the hot wire and become audible. It’s of course not, but it is significantly easier, so much more of the current flows through the ground. It’s actually a matter of voltage division, but we don’t really need to go there now.

The other way to look at it, which actually makes more sense to me in more situations, is that the amplifier is sensing and amplifying the difference between the “hot” and “ground” wire. If one of those wiggles when the other doesn’t, you end up hearing it. EM noise is going to wiggle the wires, but if we can make sure it wiggles both in the same direction and by the same amount and at the same time, then the difference between the two remains zero, so we shouldn’t hear it. This is not exactly the same as the HB thing, but many of the principles - and limitations - are the same. We’d still prefer for the two wires to be exactly the same and in exactly the same place so that both amplitude and time/phase will be exactly the same. We physically can’t, though, so we try to get them as close as possible and kind of hope for the best.

Most of the time if one cable is noisier than another, it’s because it has more resistance, which messes up one of the other of those two mechanisms.

[reTrEaD]

Dec 21, 2020 3:34:02 GMT -5 pyrroz said:

Why does grounding the bridge actually works?

Bridge (string) grounding works because ...

You're just a big ole' Bucket O' Noise

---

HBs are less susceptible to external hum and noise but to say they don't need a bridge ground is misleading. Because the cancellation of external hum and noise is less than perfect, they will still benefit from a bridge ground.

Also, if a HB is split to a single coil it won't benefit from hum-cancellation when it's the only pickup selected. In that situation, a bridge ground is just as important as it is for SC pickups.

[bubbalou88]

As previously stated, humbuckers are not perfect. Some much better than others. If both coils are not wound close to the same number of terms you may get some noise in noisy environments. Also the body acts like an antenna to noise. If your bridge, strings etc are properly grounded then when you touch the grounded metal you become grounded and the noise is suppressed to some extent. There are other factors. I have long felt that coils when wound where the outer coils connect to ground or in case of humbucker outer wires in the coil connect to the next coil that has it's outer wires connected to ground they will be quieter. 

[pyrroz]

Dec 22, 2020 12:56:37 GMT -5 ashcatlt said:

If newey got it from me, it was only because I was repeating what somebody else around here had explained previously.

But yeah, if you happen to have a pickup whose pole pieces are not themselves grounded, and you manage to touch one of those pole pieces without also touching the strings, you should notice that the noise gets significantly louder. The noise from your body is being focused right in the middle of the coils where it can be most easily transduced. Our bodies do generate their own noise (you are an electrochemical machine), but also tend to somehow collect and focus the EM/RFI noise in the world around us.

Humbuckers work via phase cancellation and that depends on a strong correlation between the two signals. For perfect cancellation, they need to exactly the same amplitude and exactly in phase which is to say time aligned. If the two coils of the humbucker were exactly the same and in exactly the same place, they would pickup every noise source exactly the same and cancel perfectly. But of course they aren’t and can’t be, so they don’t. Any given source is going to be louder in one or a little earlier or both. When it comes to time alignment, lower frequencies are “more forgiving” in that you can have longer delays between the two signals and still get at least some cancellation. I think that’s maybe why humbuckers tend to buck hum (lower frequency noise) better than hiss (higher frequency noise). What I tend to call buzz is actually distorted hum - some low fundamental noise with harmonics that extend into the higher frequencies - and sometimes a guitar will do a great job of cancelling out the lower frequencies but you can still hear those annoying high harmonics.

Shielding and string ground I think work somewhat differently. There’s kind of two ways to look at it, and I actually think both are true to some extent, but neither actually have to do with anything being drained away. It’s all about completing a circuit.

One way I’ve seen it explained is to imagine something like a radio antenna. One end is connected to the actual earth, and the other end is up in the air. The signal is capacitively coupled to your guitar and wants to complete its circuit back to the antenna. It can get there through the hot wire of the guitar, but that is a high impedance path, and if it can get there via a a lower impedance path like the ground wire, it would “prefer” to do so. If the ground path is actually 0 ohms all the way back to the antenna, then the noise source is essentially shorted before it can get to the hot wire and become audible. It’s of course not, but it is significantly easier, so much more of the current flows through the ground. It’s actually a matter of voltage division, but we don’t really need to go there now.

The other way to look at it, which actually makes more sense to me in more situations, is that the amplifier is sensing and amplifying the difference between the “hot” and “ground” wire. If one of those wiggles when the other doesn’t, you end up hearing it. EM noise is going to wiggle the wires, but if we can make sure it wiggles both in the same direction and by the same amount and at the same time, then the difference between the two remains zero, so we shouldn’t hear it. This is not exactly the same as the HB thing, but many of the principles - and limitations - are the same. We’d still prefer for the two wires to be exactly the same and in exactly the same place so that both amplitude and time/phase will be exactly the same. We physically can’t, though, so we try to get them as close as possible and kind of hope for the best.

Most of the time if one cable is noisier than another, it’s because it has more resistance, which messes up one of the other of those two mechanisms.

GREAT POST!

Thanks ashcatlt   Here is my personal theory shaped before I read your post :

In case of 50/60Hz hum the source is a stable generator of noise with predictable characteristics and applied in a uniform manner to both coils, so the balanced coils of the humbucker are able to cancel out the noise by creating currents with mutually opposite waveform. But in the case of body/bridge/strings/computers/TV/electric motors/etc the source is not predictable nor stable and even worse is not applied in a uniform manner to both coils, some coil might be closer to the noise, or having more than one sources of noise applied differently to each coil.

By grounding the bridge we get rid of all static load on the strings or external EMI/RFI picked up by the strings/bridge, which would otherwise interfere with the disturbance of magnetic field of the pups in a non-uniform manner.

So I think it was pretty much there.

[JohnH]

I'm going to go with:

- Definitely ground the bridge if you can, on the basis as noted above, that it gets rid of hum and buzz picked up and reradiated by the human body.
- No humbucking arrangement is perfect
- The world is an electrically noisy place
- It's essential with any wiring scheme with coil splits
- Its all even more important with high gain
- There's no downside to it, providing you can access the bridge metal.