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Post by antigua on Feb 6, 2017 15:01:37 GMT -5
This is how I've come to understand the issue So you have electromagnetic noise and electrostatic noise, and the two correlate to the difference between inductance and capacitance. Electromagnetic interference is the outside world treating your rig as the other half of a transformer, and electrostatic noise is the other electrical devices sharing the same electrical source treating your rig as the other side of a large capacitor.
So you touch the strings, the electrostatic noise reduces, and using the capacitor analogy, it has reduced because by touching the strings you've made one "plate" of the capacitor a lot larger, so more static interference now routes though you instead of the guitar's circuitry.
If this is all stated correctly, how much difference would cavity or pickup shielding really make when your body is doing so much to diffuse the area over which static noise is absorbed? Is shielding only really relevant in those rare cases when you are both not touching the strings and also have your volume up full?
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Post by newey on Feb 6, 2017 17:01:40 GMT -5
Antigua- We've had a lot of discussion over the years about this, and you're going to gte a bunch of replies, most of which will probably explain this better than I can. First off, I don't know how much good it does to our understanding to try to distinguish "electromagnetic" noise from what you are calling "electrostatic". It is all electromagnetic radiation that we are hearing, although the sources differ. One big source is the household AC mains current, which propagates a wave (at either 60Hz or 50Hz, depending upon one's jurisdiction). Other sources include fluorescent lamp ballasts, electrical motors, neon lamps, etc. And, all this noise is, by and large, transmitted to the windings of your guitar pickups, and from there into your guitar signal where we don't want it. The idea of the shielding is to limit the area, at least on 3 sides of the pickup, where noise can be picked up. The reason that things get more quiet when you touch the strings is not (as I understand it) that you body is diffusing the noise; rather, the noise is coming from your body, which is focusing other sources of noise. When you touch the strings, you are grounding yourself through the bridge/string ground, taking that noise to ground through the amp. As ashcatlt has put it in the past, you yourself are just a "big bucket of noise" . . .  |
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Post by antigua on Feb 6, 2017 17:34:21 GMT -5
Antigua- We've had a lot of discussion over the years about this, and you're going to gte a bunch of replies, most of which will probably explain this better than I can. First off, I don't know how much good it does to our understanding to try to distinguish "electromagnetic" noise from what you are calling "electrostatic". It is all electromagnetic radiation that we are hearing, although the sources differ. One big source is the household AC mains current, which propagates a wave (at either 60Hz or 50Hz, depending upon one's jurisdiction). Other sources include fluorescent lamp ballasts, electrical motors, neon lamps, etc. They are definitely two different things, I've seen it stated various ways. I like my capacitor/inductor analogy the best, but I've seen it stated like this also: pediaa.com/difference-between-electrostatic-and-electromagnetic-force/The main reason it's important to draw the distinction is because humbucking cancels electromagnetic interference, because magnetic induction occurs in both coils, but humbucking can't cancel electrostatic noise, because it is not a changing magnetic field, where as shielding is the other way around, it can't stop changing magnetic fields, because they change too slowing to be absorbed by thin shielding, but shielding does block electrostatic interference, because it gives the noise source something else to capacitively couple with other than the circuitry of the guitar. It's true that electromagnetism is a single thing, but as the quote above says, the difference is in how the "noise source" relates to the "signal wires", maybe in terms of their relative phase, I'm fuzzy on that part. The reason that things get more quiet when you touch the strings is not (as I understand it) that you body is diffusing the noise; rather, the noise is coming from your body, which is focusing other sources of noise. When you touch the strings, you are grounding yourself through the bridge/string ground, taking that noise to ground through the amp. As ashcatlt has put it in the past, you yourself are just a "big bucket of noise" . . . I don't believe that's the case. If that were true, the guitar would become progressively louder as you approached it, before you contact the strings, but it seems that the noise is just as loud no matter where you are in relation to the guitar, before making physical contact. Going back to the theory, your body cant be focusing electromagnetic fields because we are non-magnetic, and it can't focus electrostatic energy because we are not part of the relative circuit, and once we become part of it by touching the strings, we do focus, or attract, the static charge, but as I'm contending, to the effect of drawing it away from the guitar's circtuits. The opposite is also true also, if you touch a hot lead, you draw static interference to the hot side of the guitar, and cause the noise to become even louder. |
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Post by antigua on Feb 6, 2017 18:35:13 GMT -5
Another observation, based on the theory, if the key ingredient to quiet operation is total capacitive surface (of which our body provides a lot), then the benefit of shielding might also be to simply increase the amount of conductive area in total, so a guitar could theoretically be made quieter just be having a lot of metal surface involved, either buried in the guitar, or as a part of it's finish. Perhaps conductive paint covering the whole body, for example.
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Post by newey on Feb 6, 2017 23:18:21 GMT -5
antigua- Your knowledge of electrical theory is no doubt superior to mine, so it won't surprise me if I stand to be corrected, but I'm unsure about the statement: Seems to me that electricity and magnetism are just flips sides of the same coin. There is a corresponding electrical field associated with our bodies, applying a galvinomator across one's skin will demonstrate that. But isn't it all moving? An electric motor propagates a wave of noise the same way household wiring propagates a wave, the frequency and amplitude may vary, but it's nonetheless moving . . .or so I'd been led to believe.  |
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Post by sumgai on Feb 7, 2017 1:13:42 GMT -5
antigua,
I'm not going to agree with your analogies, sorry to say. The first thing I want to remind you of is the obvious - if you read it on the innerweibs, then it must be correct. Hoo yah! </sar>
When I went to school, electrostatic was compared to a "white noise" of static charging and discharging in varying cycles. Stated another way, by its very definition, static doesn't charge and discharge repeatedly in a cyclic manner. Thus, the frequency will be "indeterminante", and the ear will perceive what we commonly call a static noise. At no time can this noise be called a hum, because again by definition, a humming noise is very cyclic, a continuously repeating tone that is non-musical in nature, but nonetheless can be measured as having a basic frequency... quite easily in fact.
It is important to keep in mind that you can have one without the other, but in most non-pristine environments, you'll find both to some degree. Shielding your axe with almost anything that reduces hum also reduces static-y noises, trust me on that one.
As to your body being inherently non-magnetic..... when's the last time you had an MRI?  Hint: If your body did not respond to magnetism, you'd find that the MRI scan would return Zero results (and thus the doctors wouldn't use it). Additionally, you wouldn't be able to be shocked by any electricity - magnetism and electricity are that intertwined. Trust me on that one, too.
HTH
sumgai
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Post by antigua on Feb 7, 2017 2:14:48 GMT -5
But isn't it all moving? An electric motor propagates a wave of noise the same way household wiring propagates a wave, the frequency and amplitude may vary, but it's nonetheless moving . . .or so I'd been led to believe. It's all moving, but the difference is apparently in what it's moving: current or voltage, high frequency versus low. This website talks about electrostatic interference on this page members.ozemail.com.au/~tabbler/GndRule/GndM02.html and electromagnetic interference on this page members.ozemail.com.au/~tabbler/GndRule/GndM03.html . So you get more electrostatic interference when you have higher frequency alternating voltages, and you get more electromagnetic interference when there is more low frequency alternating current. An interesting note from the second link: Everyone knows that the amount of hum or buzz you hear depends on the angle you standing at with your guitar, and so the question is: am I reducing electromagnetic interference by standing perpendicular to the electromagnetic interference, or am I reducing electrostatic interference by putting my body between the guitar and the source of an electrostatic interference? I suppose the next time it happens I can figure this one out pretty easily. The resource doesn't really address the point of the thread though, is that capacitive coupling, which is what is supposedly happening with electrostatic interference, would have to follow the regular rules of a capacitor. You have two plate to the capacitor, the electric field distributes uniformly around the plate because the like charges on that plate hate each other and try to put distance between themselves, as depicted here:  So the source of the interference is one side of this capacitor, and you and the guitar are the other side of the capacitor, by touching the strings, it seems to me that you make the "plate" on your side much larger, drawing potential away from the guitar's lead wiring, which you are trying to protect. I'm not sure if I got that right, but it makes sense from what I've gathered so far. As an experiment, I connected the strings by alligator clip to a large stainless steel pot to see if that would reduce the noise the same way a human body does, and it did. It doesn't seem to be necessary for you or the stainless steel pot to be in between the guitar and the noise source, by simply being part of the ground circuit, you/it reduce the noise. My theory is that your body simply gives the source of noise something else to capacitively couple with, other than your guitar's wiring. |
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Post by antigua on Feb 7, 2017 2:27:30 GMT -5
antigua,
I'm not going to agree with your analogies, sorry to say. The first thing I want to remind you of is the obvious - if you read it on the innerweibs, then it must be correct. Hoo yah! </sar>
When I went to school, electrostatic was compared to a "white noise" of static charging and discharging in varying cycles. Stated another way, by its very definition, static doesn't charge and discharge repeatedly in a cyclic manner. Thus, the frequency will be "indeterminante", and the ear will perceive what we commonly call a static noise. At no time can this noise be called a hum, because again by definition, a humming noise is very cyclic, a continuously repeating tone that is non-musical in nature, but nonetheless can be measured as having a basic frequency... quite easily in fact.
It is important to keep in mind that you can have one without the other, but in most non-pristine environments, you'll find both to some degree. Shielding your axe with almost anything that reduces hum also reduces static-y noises, trust me on that one.
As to your body being inherently non-magnetic..... when's the last time you had an MRI? Hint: If your body did not respond to magnetism, you'd find that the MRI scan would return Zero results (and thus the doctors wouldn't use it). Additionally, you wouldn't be able to be shocked by any electricity - magnetism and electricity are that intertwined. Trust me on that one, too.
HTH
sumgai
Do you disagree wholesale with what is stated on this web page members.ozemail.com.au/~tabbler/GndRule/GndM02.html ? It might be wrong, if it is I'd like to know, but I wonder if the problem isn't one of terminology rather than concept. MRI machines have to use very powerful magnets to exploit a magnetic effect upon protons in water molecules. Bodies certainly aren't magnetic in the way that the term is usually meant. In fact water is diamagnetic. |
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Post by sumgai on Feb 7, 2017 19:58:59 GMT -5
antigua,
What I've learned over the last decade or so is that I no longer "know" Jack Scheiße. It happens to most of us, so I can't kick and/or complain that I'm special, 'cause I'm not. What's happening though is that things are changing over time, including what (literally) everyone else is now accepting as the 'correct definition'. What those people don't know, most of them having been born well after Viet Nam*, is that there's a pretty hefty paradigm shift going on, and I don't think it's going to let up anytime soon... Which brings me to having to admit that what I used to know is now null and void. (For proof of this, go back to when I first joined in 2005, and watch some of my antics as I rant and rave about these changes, as they are sprung on me. Yikes!  )
And all of that now boils down to: I'm not interested in who's correct, nor if someone can link to/quote from more citations than I. All I'm interested in, as a private person, is that I can make my motor run each morning. (To quote cynical1, that's a privilege denied to many!) In terms of my public persona, I'm really only interested in the welfare of The NutzHouse. When I see something that looks like someone's about to become a crispy critter, that's a safety issue upon which I will jump with both feet. When it comes to matters of the wallet, I'll drop my advice-bomb, and then let it go. Everything else, I don't really care enough to engage more deeply than an initial "consider this....". If things become contentious, then I back off - no need for me to muck things up with my misfiring memory, or so I like to think.
Tends to keep The NutzHouse on a more even keel, as the growing number of core members would seem to attest.
TL;DR:
I may disagree with everything you'e said and possibly every source you've linked to, but the bottom line is that you have to dope it out for yourself. Just knowing that one other person on this planet has an issue with the quoted sources should be a clue that you need to do further research, and not just here on this site. (At least it I would take it as a clue.) Good luck!
For extra credit, after you make up your mind, you should consider sharing your findings. 
sumgai
* Fun fact number 1: More than half of all the people who have ever lived on this planet... are alive today!!!!!
Fun fact number 2: 90% (or more) of all scientists who have ever lived are alive right now! You no longer need wonder at our rate of progress. You also no longer need wonder at the vituperitous contentions between many of those same scientists. After all, they are human. Smart ones, but still.....
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Post by reTrEaD on Feb 7, 2017 22:24:36 GMT -5
I no longer "know" Jack Scheiße. Surely you remember his cousin Earl.  |
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Post by reTrEaD on Feb 7, 2017 22:30:36 GMT -5
I don't believe that's the case. If that were true, the guitar would become progressively louder as you approached it, before you contact the strings, but it seems that the noise is just as loud no matter where you are in relation to the guitar, before making physical contact. It's been my experience that when I bring a poorly shielded guitar in close proximity to my body (without touching the strings) the hum is worse than if it is just sitting on a stand. YMMV. |
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col
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Post by col on Feb 8, 2017 3:36:36 GMT -5
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Post by sumgai on Feb 8, 2017 12:17:43 GMT -5
col,
It's hard to know even approximately just how many people have ever lived, I'm sure. But for me, the first fact simply sets up the zinger of the second one, about scientists. Which was more of a sideways (and hopefully polite) way to say that anything that can be denominated can also be contested, it just seems to be human nature.
I could go on, but like I said above, my soapbox is starting to tilt dangerously in the direction of me falling off, so......
sumgai
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col
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Post by col on Feb 8, 2017 16:14:33 GMT -5
Yeah, sumgai, the number of scientists is the more interesting number here. And it is somewhat comforting when compared with the commonplace attacks upon science, facts and 'experts'. You may not be aware, but before the Brexit vote, a senior British Government minister somewhat infamously dismissed the opinion of highly regarded economists by stating "people in this country have had enough of experts". www.ft.com/content/3be49734-29cb-11e6-83e4-abc22d5d108cwww.telegraph.co.uk/news/2016/06/10/michael-goves-guide-to-britains-greatest-enemy-the-experts/Unfortunately - although the thrust of Michael Gove's comment was wrong (and stupid) - it seems that he was right about the British people (and other peoples). It is probably best that I stop my comments here. |
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Post by sumgai on Feb 8, 2017 17:08:12 GMT -5
col,
Thanks for those links, I hadn't been aware of Gove's gaff. 
Ya know, do you read science fiction? Well over half a century ago there was an author by the name of Jack Vance. He wrote a tome called "The Languages Of Pao". Even unto this day, his treatise epitomizes just how we so easily misinterpret what a speaker intended for us to understand, as we communicate with each other. I gave up my paperback copy of that (and about 2200 other SF books) earlier this year, so I can't just ship one over to ya, sorry to say. 
sumgai
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col
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Post by col on Feb 8, 2017 17:51:30 GMT -5
I wouldn't describe Gove's comment as a 'gaff' - he said exactly what he meant to say. And, as I mentioned earlier, he seems to have been proved right! That's just mind-boggling. This is how so many people think these days. I find it very distressing. I'll look up that book. I sometimes read science fiction. I worked my way through the whole Foundation series (and some associated 'robot' stories by Asimov) a couple of years ago. Good stuff! By the way, reading between your words, I think you are under the impression that I am in the UK. I am British, but live in the US. On both sides of the pond, we now live in interesting times*. * I have only belatedly come to understand that the 'interesting times' phrase is actually an old Chinese oblique curse: en.wikipedia.org/wiki/May_you_live_in_interesting_timesSorry - I'm derailing the thread. |
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Post by antigua on Feb 8, 2017 20:28:08 GMT -5
It's OK, consider the official topic closed. It was a vague premise to begin with.
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Post by sumgai on Feb 9, 2017 0:43:06 GMT -5
antigua,
It's not vague if it engenders discussion. The fact that we kept it civil probably goes a decent ways towards relieving some of col's anxieties. 
col,
I hope you're keeping your passport and visas up to date! 'Nuff said.
sumgai
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Post by blademaster2 on Feb 9, 2017 14:58:05 GMT -5
Hello all,
I must confess that am not entirely clear on the relationship between the human body and noise being increased or reduced when touching the guitar shield. What I *am* clear on is that electrostatics deals with static electricity (not changing over time) like the charge built up before getting a shock after walking across a carpet and touching a doorknob or other metal. (Oddly enough, I *do* get some noise from electrostatic discharge in the Canadian winter when I slide my hand up the neck and it causes tiny discharges from my skin along the lacquer finish that, somehow, couple into the strings and produce a crackling sound through the amplifier).
However, having studied electrical engineering I can say that electromagnetic fields consist of both a magnetic field component and an electric field component. Both can cause interference in different ways, and for that reason to propagate low level signals and keep them from picking up radiated noise is usually accomplished using twisted/shielded pair cable and driving them from a balanced source (where the impedance to ground on the positive and negative lines of the twisted wire are the same). In that type of system, different from a guitar where it is unbalanced, the shielding prevents pickup of voltages from electric field interference (measured in volts/metre) by preventing it from penetrating into the shielded location - effectively shorting it to ground - and the twisting cancels out the magnetic field (measured in amperes/metre) that each of the twisted wires picks up by ensuring that they both have the same induced signal on them and therefore can be rejected by a balanced receiver (same impedance to ground on both signal inputs). A perfectly twisted wire, i.e. with perfectly even twisting, will reject frequencies up to a limit represented by half of the electromagnetic wavelength of the dimension of the apertures formed along the length of the twisted wires.
Here is how I apply the above to the electric guitar as a system:
Electric guitars are unbalanced, high-impedance 'single-ended' signal sources feeding a high-impedance input of a guitar amplifier through the unbalanced, shielded guitar/amplifier cable. A non-zero resistance of the shield (nothing is perfect) will permit the electric field noise from appliances and lights to create noise in the signal. Magnetic fields, just like the fields that are rejected by the twisting of twisted/shielded pair cables, cannot be shielded out and instead are canceled by creating a balanced signal source at least at the guitar end of the set up - which gives us the humbucker pickups. Those pickups will receive magnetic field interference (usually a 60Hz 'hum') on each of the two coils, but they have reversed directions in their windings and therefore the hum from one is canceled by the negative version of the same hum from the other when they add together. The signal from the strings, however, is generated by the string dragging around the magnetic fields of the permanent magnetics of the pickups, so when the magnets are reversed from one coil to the next it causes the voltage of the desired signal to be reversed a second time and instead reinforces the signal rather than canceling it (humbuckers have more - roughly double - signal strength compared to single coil pickups). The downside is that, as a signal source, humbuckers have double the inductance and resistance and will lose higher frequencies through the cable and (lesser extent) amplifier input capacitance. They also have a wider area to sense the string and also lose high frequency tone by the averaging of the vibrations across this wider aperture.
So in essence, a humbucker-equipped guitar addresses magnetic field interference only at the pickup itself and is thereafter treated as a high-impedance single-ended signal source from the output jack to the amplifier. As such, for the frequencies of interest a guitar is not bad, in theory, for generating reasonably noise-free signals. (Microphones, on the other hand, mostly produce balanced signals with low impedance and are carried on twisted/shielded pair cable ((called microphone cable)) into a balanced XLR input rather than a single-ended guitar jack input).
I apologize if this lengthy post is boring .....
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Post by sumgai on Feb 9, 2017 17:23:39 GMT -5
Hmmmm,
Ya all know, I don't ordinarily go in for long-winded diatribes about things that quickly get so technical that 2nd, or even 3rd year student EE's find themselves running for the Excedrin. I understand that not all of us want to know the hoary details, etc. But the above post by blademaster2 works fairly well. I would debate one or two points just for the bedevilment of it, but that's not why we're here, nor how we (most of us) get our kicks, amiright?
At this time, all I want to say is, remember the ChrisK-ism - "The best cables are made of RF". They don't hum, no matter how much or how little shielding is installed into your guitar. They. Just. Don't. Hum. Period.
Most players buy them for the convenience, and some for safety reasons (how are you gonna get shocked when swallowing a microphone?), but everyone vows keep to theirs forever about 5 seconds after they get the surprise of their lives - the guitar is now, and forevermore, quiet. As in, no hum or any other BS noises. That 'quiet' attribute might be the deal-maker for many players, but I have to admit, units of any quality are not cheap.... you can buy a new ESP or Schechter for about the same amount of moolah. Going digital, that raises the bar into the low-end real Fender category. But the upside is, they last forever, providing that you don't submit them to the "Drunk" test - that's where you receive uninvited drunks up onto your stage, and they proceed to stumble/stomp all over your gear, usually breaking only the most expensive stuff.
I have an old Guitar Bug, made by AKG, and it still works just like it said on the tin (said tin now inhabiting a rubbish bin, somewhere in North Americal). they don't make them anymore, the company would rather have your dollars for digital gear, but if you find one used (craigslist, eBay, etc.), I'd say you should give it some serious consideration.
Speaking of eBay, I just learned that Pyle and someone called Premier now offer similar units in the $150 USD range. I know nothing about them, but the transmitter unit shown in the picture looks just like my Bug. Search for them under the term "guitar bug wireless system".
HTH
sumgai
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Post by newey on Feb 9, 2017 22:09:36 GMT -5
I think that's a great explanation, blademaster2. But, pray tell us, how/where does the human body enter into it? Not to put this thread back on topic or anything . . . |
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Post by ashcatlt on Feb 10, 2017 0:29:26 GMT -5
Oddly enough, I *do* get some noise from electrostatic discharge in the Canadian winter when I slide my hand up the neck and it causes tiny discharges from my skin along the lacquer finish... This reminds me of a thread that happened over at homerecording.com a while back. I though about bringing it here, but...I have excuses... Dude was complaining about getting noise when he was playing and his hand brushed the pickguard. I was completely convinced it was microphonic pickups actually microphonically picking up his hand brushing the guitar, but a whole bunch of people jumped on to say that it was discharge of "static" electricity being induced into the circuitry. People went so far as to say they always keep a bottle of anti-static spray (like you might spray on clothes to stop the Static Klingons) in their gig bag and blast their guitar with it before playing. Almost thirty years playing. Never heard of, needed, or even considered such a thing, but... If it's "static", then it ain't moving and it ain't changing and it ain't noise. Imagine a battery. it has a pretty significant amount of charge stored up as static electricity. Put that next to your pickup, and you're not going to hear anything. Connect it across your cable. You'll hear a pop as the connection is made, and then silence. Theoretically, though, if you connect one end of that battery to one side of your circuit, and move the other end around, even though the charge stored in the battery won't change, you'll end up "hearing" something. This is how Wurlitzer electric pianos work. An actual static electric charge won't induce noise unless A) it shares a reference with your circuit AND 2) It moves in space with respect to your circuit. Capacitors (and capacitive coupling) block DC. Doesn't help us much. I can tell you for sure that when I rest my pinky on the blade of one of my GFS Lil Killers, I hear the noise. All of whatever my body is doing gets focused right in between the pickup cools where it can do the most damage. All metal pole pieces will do the same. Also, have you ever touched the tip of your guitar cable when it was plugged in an turned up, or wired your jack backwards? I'm not so sure nowadays how much I buy the idea of shielding as "blocking" or "shorting to ground". Ground isn't actually a real thing. All voltage is relative. All that matters to your amplifier is really the difference between the tip and sleeve of the jack. If either one of them wiggle, you're going to hear it. I think most of the times shielding works because the noise of the cosmic winds wiggles both wires the same amount in the same direction at the same time. |
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Post by blademaster2 on Feb 10, 2017 13:00:36 GMT -5
I perhaps did not express the action of a shield well enough earlier. An electric field will be zero within a conductively enclosed volume, so if that conductor is shielded and the shield is grounded (to the amplifier ground, which is often earth ground but not always) then any electric field directed at the conductor will not be able to induce a voltage inside of it (shielded from it) and it will ground out the value to zero. It is also true that the voltage will be taken to zero whether or not it is connected to earth ground. Either way it will cause a reflection of the electromagnetic energy and cause that electric field to propagate in the reverse direction and create standing waves as it interferes with the incident electromagnetic waves. The directionality of electromagnetic emissions, their propagation and these multipath reflections from conductive materials, creates standing waves with peaks and nulls throughout our environment. That is why it changes if the guitar is moved or rotated (and why Steve Morse says he will 'map out' the stage before a concert to see where and how he needs to hold his guitar to minimize noise and he will go there for quiet passages of the music).
So yes, a conductive shield shorts out the voltage portion of a electromagnetic wave - but not necessarily to ground (grounding it helps since you can separate grounded conductive materials and they can all still have the same potential on them). It also prevents that electric field from being formed within it. However a shield does not do the same for the magnetic field component of the electromagnetic wave and that is why some systems (not guitars) also add twisting of balanced conductors to cancel out magnetically-induced noise.
Understanding something vs being able to clearly explain it are sometimes not the same thing for me.
[Sorry, sumgai, for giving people even more reasons to take Excedrin..... I am curious which points you would debate, and I freely admit to not being an expert in all things electromagnetic]
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mr22
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Post by mr22 on Jul 21, 2022 0:24:02 GMT -5
Hello Antigua,
I think this is a useful way to think about the origins of the "buzz that goes away when you touch the strings."
I replicated your experimental results and did a few other small experiments that are consistent with your hypothesis and contradict the "humans are a bucket of noise" hypothesis.
(1) I plugged into an amplifier that had an audible buzz that was reduced when I touched the strings. I put my amplifier on normal playing volume, about 75db when I play a chord. (I live in an apartment building, can't go much higher than that.) I moved my guitar away from me by up to 2 meters and the volume of the buzz did not decrease audibly. Since the strength of EM fields should be inversely proportional to the distance raised to a power of 1 or greater, increasing my distance from the guitar pickups and circuits from about 5cm to 1 meter should have yielded at least a 97.5% drop in the intensity of the field that could be picked up by the circuits or the pickups. A 97.5% drop should yield about a 16dB drop in the buzzing noise, about the level of common mode cancellation that is provided by active pickups. Nothing even close to that amount of noise reduction was audible. The buzz remained the same.
(2) I used an alligator clip to attach my strings to a large metal object. The volume of the buzz dropped greatly when I attached this object. Attaching a metal object to the guitar should not affect the amount of "noise" that my body was giving off.
I did two other simple experiments.
If humans are a source of the buzz, then doubling the number of humans near the guitar's electronics should increase the volume of the hum. I asked my partner to stand in front of me when I was wearing the guitar so we were both equidistant from the guitar's electronics. Neither of us touched any metal part of the guitar. Assuming that we generate the same amount of noise, the noise should have doubled, leading to a 3dB increase in buzz. That should be audible, but I couldn't hear any difference.
If humans are the source of the buzz, then the buzz should be audible even when the guitar is plugged into a battery-powered amplifier or wireless system. I plugged by guitar into a 9V battery powered Joyo American Sound and then plugged a 1/4 mono to 1/8 stereo adapter into the output and listened to the output on studio monitor headphones. When I played guitar through this setup, there was no "buzz that goes away when you touch the strings." If I was serving as an antenna for noise generated by the appliances and mains power in my house, I should still be an antenna even if I'm plugged into a battery-powered device.
When I plugged the Joyo American Sound into an ungrounded AC adapter, I got the "buzz that goes away when you touch the strings." This suggests, like you and other people have mentioned before, that the buzz is caused by being part of the big circuit that is your house power.
When my Joyo was connected to the wall, I set a multimeter to the 200m V setting and touched one terminal to my hand and the other terminal to the high e string. The multimeter showed a quickly alternating voltage of small amplitude. When I unplugged the Joyo, the voltage started out at 50 and then quickly reduced down to almost nothing. When I do the same multimeter test with my guitar when it is unplugged, the magnitude is 00.5. This result suggests that when plugged into AC power, the AC power is inducing an electrostatic charge
I did a third experiment that showed that my hand generated some small amount of noise but my amp had to be cranked to nearly dangerous levels to hear it. I plugged a single-coil equipped guitar into an amplifier that generates "the buzz that goes away when you touch the strings." The amp, a Boss Katana MkII 100, had to be cranked at 100w for me to hear any human-generated noise. The "buzz that goes away when you touch the strings" was quite loud. I moved my hands very close to the pickups and I heard a high-pitched hum -- not 60hz -- that increased as the distance decreased. However, the volume of this hum was much, much less than the volume of the buzz. The buzz, once again, did not decrease in volume when I moved away from the guitar -- even when I moved out of the room entirely .
These results are consistent with your claim that when you plug in with mains power, then the guitar circuit is capacitatively coupled with the AC power in the house, generating electrostatic buzzing in the signal, and that when you touch the strings then you reduce the charge density of the capacitor, thereby reducing the volume of that electrostatic noise. This would also explain why there is no "buzz that goes away when you touch the strings" when I use a wireless system to connect to my amp, but the single coil hum is still present. No connection to the circuit, no capacitative coupling. The presence of 60hz alternating magnetic fields in the air does not depend on whether I'm a part of the circuit that is generating them.
The capacitative coupling hypothesis would also explain why there is no "buzz that goes away when you touch the strings" when your amp is properly grounded to the power source in your house. The wires connected to house ground are connected to several large conductive objects, which become one side of the capacitor. Grounding to literal earth ground instead of using the power source panel ground should also work for killing buzz because the earth is a "very large plate" and any charge built up from capacitative coupling should have a very low charge density.
I thought about getting an isolation transformer to kill the buzz and to increase the safety of playing a guitar in my home. (I live in a country where almost none of the outlets are grounded.) If the capacitative coupling hypothesis is correct, then using an isolation transformer shouldn't eliminate the buzz, it should only reduce its volume. Plugging into any AC circuit will cause the capacitative coupling noise phenomenon, even if the AC system is your isolation transformer? I guess wireless is the best choice both for noise prevention and for safety.
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Post by gckelloch on Dec 22, 2022 14:52:02 GMT -5
I think only one blade of those GFS pickups is connected to the ground wire. A piece of conductive tape across the blades would fix that.
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Post by stevewf on Dec 22, 2022 22:50:35 GMT -5
I think only one blade of those GFS pickups is connected to the ground wire. A piece of conductive tape across the blades would fix that. The GFS Li'l Killer that I got (for Bridge position) had both blades soldered to the ground wire. One of the solder joints broke, though, and I had to redo it... which was a pain because my solder wasn't sticking well to the blade. I may be that those solder joints tend to break. |
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Post by gckelloch on Dec 23, 2022 0:27:55 GMT -5
An old Lil Killer my brother had did not have a wire connecting the blades. It may have fallen off. He connected them with Cu tape just for good measure.
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Hint: If your body did not respond to magnetism, you'd find that the MRI scan would return Zero results (and thus the doctors wouldn't use it). Additionally, you wouldn't be able to be shocked by any electricity - magnetism and electricity are that intertwined. Trust me on that one, too.
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