Grounding, shielding, and Tele tone

[tpaul]

Originally Posted by 0le FUZZY

...All TELECASTERs are li kat. Touch the control panel, touch the neck P/U, touch the jack cup. If the noise goes away any time yew touch metal then yew are grounded properly.

...Lights, dimmers and a number of udder thangs will cause noise threw yer amp in any giffin venue.

...I never shield a TELECASTER. It dulls them up and deadins the sound and will knott screen out the noise from a light dimmer that iss of the old style.

Fuzzy, I've been reading your posts here for most of the decade and I thought I got it, but this quote has been rattling around in my head since I read it last week and I just had to respond.

I always thought what you describe above indicated a grounding problem.

Now at last I think I understand what you are trying to tell us about how alive a Tele should sound. I'm not sure I can live with the hum, but at least I get what you're saying.

What I don't understand is how shielding, or more thorough grounding, would reduce the tone. Wouldn't cutting back the hum let more of the musical tone from the instrument come through in the mix?

I don't expect you to have the answer but maybe there's an electrical engineer reading this (maybe you) who can shed some light on the story.

Anyway, at least you know a few of us actually think about what you type here and try to further our own understanding.

Thanks,

Tpaul

[0le FUZZY]

...I gar-on-tee-tolt yew there issa lectric engin-ear gonna reed iss.

...His name iss Terry Downs and he could store my noll-lege of lectrics in his rite watch pocket of his jeanz and still haff room fer his gran-papa's railroad watch.

...I kant even come close tew splainin watt the RF and capacitance and ambient lectric currents all dew er don't dew inna TELECASTER with stuff stuck in and roun all the holes.

...My state-mints are based on my experience here and on stage.

...Alst I noe iss that whence a TELECASTER makes a noise I kant stan I git busy with the surrondings rather than stickin a bunch of aluminum, brass, copper and or groundin wires in it which I haff dunn many many times inna past.

...If I don't hear a click whence I use the pick onna bridge shoulder or don't hear a click whence I switch from lead tew the middow position I noe I gotta change sunthin in my TELECASTER.

...The list is long of items in certain venues that will affect/effect the lectrics runnin from the amp tew the TELECASTER and back again. Sum cannot be fixed but rather need tew be shut off such as lite dimmers ect..

...All TELECASTERs are li kat. Touch the control panel, touch the neck P/U, touch the jack cup. If the noise goes away any time yew touch metal then yew are grounded properly.

...Yes I beeleb that!! and the onlee way around that iss tew make a solid ground tew yer body which I haff dunn.

...I wonce played inna club where iffin I turnt the TELECASTER loose tew clap my hands with the ress of the band or grab a quick drink the noise wood drown out the P.A. system. I jes modified my Esquire with a wire from the neck P/U into the neck pocket hooked tew the screws onna neck plate with a nutter wire stuck in my waist band inside my pants from the screw onna neck plate. A nutter way was tew run a wire tew my wrist watch or the snaps on my wrist bands.

...Over time I lernt tew hit that volume pot and turn it all the way down erry time I wassa gonna turn the TELECASTER loose in any way.

...If yer TELECASTER hums bad with the volume down leaned up again yer amp then yew haff a prollem that noe shieldin issa gonna help.

...This subject iss jes like Poly vs Nitro, Ash vs Basswood, Maple vs Rosewood neck, brass vs steel saddles and all the udder thangs we argue bout here and Yer Milage May Vary and Tew Each Hiss (Her) Zone.

...Fer me the raw, ringin, twangin, raunchy, dirty, gritty, clackin, chime-like sound iss --------------TELECASTER.

...Course yew could reach back and switch the ground switch HEE! HEE!

...Sorry I kant splain better but even iffin yer cord is good and yer amp iss proper and yer grounds are all kerrect yew gonna git sum hum iffin yew leaf the volume up and lean yer TELECASTER back onna amp all by its own seff.








(deranged internet-based alter ego, with my own lexicon and all.)

Please visit my page

[Drak]

What I don't understand is how shielding, or more thorough grounding, would reduce the tone. Wouldn't cutting back the hum let more of the musical tone from the instrument come through in the mix?

If you want a quick down and dirty answer, try removing the cover from your neck pickup, experience the tone with and without the cover (which is a shield).

That may get you where you want to be with your understanding of shields and interference and whatnots...

And as Fuzzy said, to each his own. I like to shield, I like to use pre-amps, I like to use various tone-shaping pots inside my guitars, so I HAVE to shield, and I'm as perfectly happy with my Telecaster tone and twang-factor as Fuzzy is without all that stuff.

It nice to live in a world of choices, there was a time when none of these things, or even the knowledge, was available to us the way it is today, so choices are good, what you do with your choices is up to you, and hopefully you'll be happy with your choices and make a joyous Telecaster noise unto Leo with them.

[Jim.Collins]

What is a tone control? It is a capacitor coupled with a variable resistor, and it sends some amount of highs to ground.

Everything as some level of capacitance, including all that shielding foil. It may be small, relative to the value of a tone cap, but it is there. For the shielding to work, it has to be grounded. Right there, you have a fixed tone control.

[tpaul]

I would very much like to hear from Mr. Terry Downs on this topic.

I am not trying to start a debate, but rather to learn about a topic on which I am generally ignorant.

I am making a couple of assumptions that may be incorrect:

1) shielding is not the same as a tone control, in that your signal is not being routed through the shielding before going out to your amp.

2) the so-called 60-cycle hum is not the same as the signal generated by your strings vibrating over your pickups, in that it enters the signal chain at some other point and is generated by electrical "noise" from dimmer switches, flourescent light ballasts, etc.

If these two assumptions were correct, shouldn't it be possible to A) shield your electronics without sucking highs from your tone, and B) reduce hum without reducing the signal from your pickups?

Again I am not trying to start an argument and I admit my assumptions may well be wrong from the get-go.

Is Mr. Downs in the house?

[tdowns]

I don’t recall saying to much about guitar shielding on here. It is a controversial subject perhaps, but I’ll try to give you some principles of what is going on with your guitar electronics.

Losing Battle
Not so fast. I’m not saying you should not shield your Tele at all, but it is impossible to make a guitar with single coil pickups totally quiet. The pickup’s job is to “pick-up” right? Ever notice that your AM radio or UHF TV antenna is a loop? A really smart man back in 1831 (before cell phones) named Michael Faraday determined that a varying magnetic field would generate voltage in a loop of wire. This is Faraday’s law of induction.



It also turns out that if you increase the number of turns in the loop or coil, the voltage output increases linearly. A guitar has thousands of turns, so it is a very high output antenna. If it is working in your guitar, it will also work to pick up stray electromagnetic fields in the room.

The other wiring loops your guitar will act as an antenna too, but not as well as the pickup does. So, shielding the control cavity will reduce some of the total hum/noise. Twisting the leads together from your pickup helps too. I think most of you find out quickly that you can rotate your body or dance around in a circle and you will find a rotational position where the hum/buzz is nearly eliminated. This is because the pickup’s magnetic field has a null position. I believe that if the control cavity is not shielded, the wiring can pick up stray fields in that null position. So, I’m not saying shielding the control cavity will work really well, but it tends to make the null point more “null”. Does that make sense?

Tone Suck? Shielding Materials?
I’ve read that phrase on here a lot before. That’s because some folks shield their Tele, they put it back together and their tone sucks. Well, there are variations all over the place on that one.

Have you ever used a metal detector? Do you know how they work? The olden days type metal detector used a Beat Frequency Oscillator approach. The unit had a big loop antenna that was the inductor in an oscillator circuit. It detects the minor change in inductor’s inductance when a metal object is presented in its field. If a ferrous object (i.e. steel) is in its field, it will cause the inductance to increase. The pitch of the audible oscillator would decrease. If a non-ferrous object (i.e. copper or aluminum) is placed it its field, the inductance will decrease. Why? Because a non-ferrous material will generate eddy currents in itself. These eddy currents turn out to be opposite to that of the field.

Now having that said, how much difference does it make? Well not much for most materials. So does the copper foil in my pickup cavity lower the inductance of the pickup that much? Well, not very much. However, aluminum is really bad for generating high eddy currents. However, it is a great low frequency shield. You can place an aluminum pan over a pickup lying on a table, and the low frequency hum will disappear. Too bad the harsher high frequency noise is still there.

Shielding does not add much capacitance to affect the tone. It is hard to get enough surface area involved as a parallel plate capacitor to ground. It does categorically increase the capacitance across the wiring, but I’m not sure how noticeable it would be.

Where is all this noise coming from?
Anywhere you have a building wired with the AC line, and there is current in the wire, there is enough loop area in the wiring to generate fields. Since your pickup is designed to “pick up” that signal very well, you get the noise. If you go back and look at the equation for Faraday’s law, you will see the d/dt. That is the rate of change of the field. The higher the rate of change, the more output. Enter…lamp dimmers. A lamp dimmer uses as triac, which is like a double back-to-back silicon controlled rectifier. A circuit delays the turn-on of the device until the AC sine wave is part-way through its cycle. Then WHAM. It is slammed on. This fast rate of change in current in the wiring generates more output than the fundamental frequency of the AC line (or 50 for you UK folks). This makes lamp dimmers very pesky items for the musician. Higher quality dimmers will have a good snubber networks to reduce the rate of change, but it will still be in the audible spectrum. Fluorescent lights are bad too, having a fast rate of change in current. This is where I separate HUM from BUZZ. Hum is a low frequency hum. Buzz is the all the high frequency (high rate of change of current) crap generated by lamp dimmers and other electrical items taking slugs of current off the AC line.

What’s wrong with your human body?
You body is a big antenna for AC fields. You know that by the buzz you get when touching the tip of your guitar cord with the other end plugged into the amp. Touching non-grounded guitar strings will connect YOU as a big BUZZ/HUM antenna to the strings and that signal will be very effectively induced into the pickups. If your strings are grounded (via the bridge plate on a Tele), the grounded strings short YOU out to ground. A shorted antenna doesn’t pick up very well. Your Tele has zapped your ability as a low frequency AC antenna, and provided you with silence...well nearly silent.

Shield or not to shield?
It is up to you. It is not a perfect solution. It will reduce hum and buzz to some degree. Perhaps the combination of pickup inductance and load capacitance (cable and amp) are such that metal shielding added will tune the resonance so it sounds better to you. Your mileage will vary.

I find that shielding is most effective and important in a guitar with noise cancelling pickups. The pickups do such a good job cancelling the noise, that the small amount you can still hear is generally a wiring pickup problem from the control cavity. This can be nearly eliminated with good shielding.

Materials
I have used the Stewmac copper foil tape and it worked well for me. You must use a conductive tape where the adhesive is conductive too. The shielding paint didn’t work as well for me, but is sure is easy to apply. At least you can remove the copper tape if you don’t like the sound change.

I haven’t noticed any tone difference with using copper foil tape. But you may on yours. All my guitars with noise cancelling pickups have shielding. I have a few single coil types that have it, but most are not.

I hope this helps and doesn’t start flames.

[chickenpicker]

Excellent, informative stuff as usual.

I have a couple of questions having read these posts: Being a skinflint, I shield all my guitars with aluminium foil taken from the kitchen while Mrs Chickenpicker's not looking. If I used copper foil instead, would there be a diiference in the frequencies affected by the shielding; would I be likely to notice any such differences in the overall sound of the guitar; and what would be the effect if I shielded the guitar with a layer of copper and a layer of aluminium?

[Ronkirn]

That was great Terry, reminds me of cramming for the 1st phone ticket.. a little knowledge goes a long way, that should make it 'round the world a few times.

Ron Kirn

[Douglas_Holt]

Very informative stuff Mr. Downs. Thank you for sharing.

Doug

[Wild Rice Chris]

Originally Posted by tpaul

1) shielding is not the same as a tone control, in that your signal is not being routed through the shielding before going out to your amp.

Actually, your signal is not routed through your tone control. The tone control adds a capacitance in series with a resistance, and sends a certain amount of the treble frequencies to ground.

Originally Posted by tpaul

2) the so-called 60-cycle hum is not the same as the signal generated by your strings vibrating over your pickups, in that it enters the signal chain at some other point and is generated by electrical "noise" from dimmer switches, flourescent light ballasts, etc.

External noises can and do enter through the pickups, as Terry Downs said, as well as through the wiring.

I generally prefer unshielded guitars, although I will usually shield when using noiseless type pickups. I hear more buzz with them that goes away with shielding. Shielding affects the response of the controls also, making treble loss on the volume more obvious, and changing the frequency cutoff of the tone control.

Like 0le Fuzzy, my statements are based on my experiences wiring many different ways and playing at home and on stage.

[Bogo]

Originally Posted by chickenpicker

I have a couple of questions having read these posts: Being a skinflint, I shield all my guitars with aluminium foil taken from the kitchen while Mrs Chickenpicker's not looking. If I used copper foil instead, would there be a diiference in the frequencies affected by the shielding; would I be likely to notice any such differences in the overall sound of the guitar; and what would be the effect if I shielded the guitar with a layer of copper and a layer of aluminium?

I think it would be more a matter of how all the frequencies would be affected. For equal thicknesses the attenuation (noise reduction) over the whole frequency range will be lower (not as good) in theory with aluminum. The connections to ground using aluminum could have higher impedance vs. copper and that will affect noise reduction. Gaps in the shielding enclosure come into play too. Doubling up aluminum or aluminum and copper would improve shielding in theory because you are increasing the thickness. I say "in theory" because I've seen no real scientific studies on guitar shielding and effect on sound. All I can go by are basic concepts and there are too many variables in each persons shielding project.
But with that said, we're dealing with materials and shielding techniques that affect frequencies from hundreds of hertz to megahertz not only in the shielding but the subtle altering of the signal path from pickup to next gain stage. The signal levels are so low to start with it may be explainable that the final signal characteristics with shielding sounds different and could be more to some peoples liking. All the stuff going on at high frequecies (harmonics) we can't hear do affect the range we can. Reduce their contribution and you change the sound to some degree.
My 2 cents worth on a subject that will never be settled in my lifetime!

[Drak]

I have a couple of questions having read these posts: Being a skinflint, I shield all my guitars with aluminium foil taken from the kitchen while Mrs Chickenpicker's not looking. If I used copper foil instead, would there be a diiference in the frequencies affected by the shielding; would I be likely to notice any such differences in the overall sound of the guitar; and what would be the effect if I shielded the guitar with a layer of copper and a layer of aluminium?

I remember awhile back Bill Lawrence posted here on this exact subject, he did an -excellent- explanation, the best I've ever seen, maybe someone could go back and find it and repost it here, it addresses aluminum vs. copper vs. carbon paint, great post it was.

A really smart man back in 1831 (before cell phones) named Michael Faraday determined that a varying magnetic field would generate voltage in a loop of wire.

Not the exact same principle, but more from the insightful mind of Mr. Faraday...

A Faraday cage is a metallic enclosure that prevents the entry or escape of an electromagnetic field (EM field). An ideal Faraday cage consists of an unbroken, perfectly conducting shell. This ideal cannot be achieved in practice, but can be approached by using fine-mesh copper screening. For best performance, the cage should be directly connected to an earth ground.

Sound familiar? Anyone who has retolexed an amp will know that shield you have to remove from the top of your amp head, either a real metal plate or the mesh screen material, is completing the Faraday Cage to protect your amplifier from picking up extraneous noises, the metal chassis material itself completing the rest of the 'cage' surrounding your signal as it goes thru your amplifier.

To some extent, by shielding the interior of your guitar, you also are making a Faraday Cage inside your guitar.
Same basic principle.

Now for the flamebait question ( ) how would you like the sound of your amplifier if all the metal shielding were removed, and you no longer used a shielded cord, just soldered two bare insulated wires to your jacks to connect everything...would that give you a more vintage sound <jk>?

Shielding your guitar's cavities is basically protecting your signal's integrity, and if you think about it like this, you have a Faraday Cage inside your guitar protecting the signal (if it's shielded anyway), then the shielded cord protecting it as it leaves your guitar on the way to your amp, then once it reaches your amp, another Faraday Cage comes into play to protect (or shield) your signal once again, and if you're using a separate cab, your signal leaves the amp thru another shielded wire on the way to your speakers, thus making a pretty complete 'embryo' of protection from pickup to speaker cone, all along the way your signal is shielded from extraneous noises entering your signal.

Anywhere along this path that you don't provide shielding for your signal, you are allowing for extraneous noise to enter, and interfere with, your signal.

Now, what price do you pay for this protection all along the line?

That is an answer only each one of us can answer, to me, the tradeoff of what I may lose in signal integrity is miniscule in comparison to the benefits provided by thorough shielding all along the signal path.

But let us now take a closeup view of a particular area of this entire signal path, let us move in closely on the pickup area itself.

A lot of noiseless pickups, if you take them apart, have the exact same copper shielding tape that is used in the control cavities, that tape is wrapped around the coil of the pickup, then connected to ground...and here is where, in this very central area, is where most of the commotion is raised.

It seems that if you overdo it in this area, that the shielding effect will start to 'choke' your signal, or 'overprotect' it to some extent, and once it is not being your friend anymore by simply offering you it's shielding abilities and is now 'muffling' your signal, well then, there might be a problem.

So, hopefully, taken in context of the whole signal chain, you understand shielding better, and can then focus the attention to right around the pickup area itself, because sheilding is necessary, absolutely necessary, until, right around the pickup area itself, it MAY, if overdone 'muffle' your signal, at that point, it is no longer your friend.

Where the point of 'friend' vs. 'muffler' comes in is where the controversy starts usually.

I guess it goes back to the old saying 'too much of a good thing is not good', or 'too much of anything is bad' comes into play.

To me, I HAVE to shield, because of the use of the pre-amps I use inside my guitars (pre-amps are, after all, tiny amplifiers, and what are all amplifiers surrounded by? a Faraday Cage! ). So my pre-amps must have a shielded cage surrounding them, something lost on most of the Clapton Booster crowd.

Now, how does, specifically, the overuse of shielding around the pickup area have a negative, or 'muffler' effect?

Well, ...I don't really know .
Maybe it's built-up capacitance, maybe it's something else, that is where my knowledge hits the cliff.

What I am trying to show here is the 'big picture' of how your signal is shielded, and any area that is not, interference can enter. That if your guitar is shielded properly, your signal is protected by two Faraday Cages, and a shielded cable is protecting it on it's way from one to the other.

THEN you can hone in on the problems surrounding how overuse of shielding directly around the pickup area itself may or may not effect your signal in a bad way.

If your guitar is not shielded at all, then it's like the head of the chain, where the signal starts, is completely unprotected, anything can enter there, then you go to all this trouble to protect the signal for the rest of the journey to the speakers, everything else is protected, or 'shielded', except the very front end, the start of the journey for the signal, the guitar itself is left open.

Remember, the neck pickup is completely covered by yet another shield (at least on top), so this leaves the bridge pickup alone as acting like a periscope from a submarine protruding above the 'shield field' waterline, the pickup itself, where it senses the strings, is not shielded in any way (unless it's a noiseless pkp, in which case the coil is shielded, but not the very top of the pickup, which is where all the action is happening. It's popping it's little head above where all shielding stops, and is wide open to anything.
If you don't use a neck pickup cover, then the same thing applies to the neck pickup as well.

I have also read that most interference a pickup picks up comes from either the top or bottom of the coil, little comes in from the sides, or so I've heard tell (maybe from Bill Lawrence, can't remember).

[Wild Rice Chris]

Originally Posted by Drak

Shielding your guitar's cavities is basically protecting your signal's integrity, and if you think about it like this, you have a Faraday Cage inside your guitar protecting the signal (if it's shielded anyway), then the shielded cord protecting it as it leaves your guitar on the way to your amp, then once it reaches your amp, another Faraday Cage comes into play to protect (or shield) your signal once again, and if you're using a separate cab, your signal leaves the amp thru another shielded wire on the way to your speakers, thus making a pretty complete 'embryo' of protection from pickup to speaker cone, all along the way your signal is shielded from extraneous noises entering your signal.

Interesting post Drak, but I do hope you're not using shielded cable between your amp and speaker?

[Drak]

Haha! Nice catch, and that would be correct, I do not, but most wires going to speakers are -twisted-, which does offer some shielding abilities.

[playanotherchord]

there are a bunch of smart cookies on this forum.. i'm glad i joined!

[RomanS]

Originally Posted by Wild Rice Chris

Interesting post Drak, but I do hope you're not using shielded cable between your amp and speaker?

Excuse my ignorance, but why would that be bad?

[0le FUZZY]

...Thank yew Terry Downs and all the rest of yew fer splainin stuff.

...Alst I noe iss iffin yew aim a mike-ree-a-fone atta amp yer gonna git a squeel and the same goes with a TELECASTER. I noe they make em in omni-directional and directional and I figger I want my TELECASTER tew be omni with in reason.

...All the noises we haff had over the years haff been delt with in many ways and iffin shieldin floats yer boat yew gotta gitter dunn.

...Yes Terry I dunn used copper and Fenner their own bad seff used luminint unner the pickguard on sum 70s and I never new why. Static letrics I reckon. I used tew werk at a factory where I could git any kind of copper sheets I wanted sew I cut a sheet that covered the hoe top of the TELECASTER and tried it. That dent werk neither.

...This kinna sums it up fer me:

Now, how does, specifically, the overuse of shielding around the pickup area have a negative, or 'muffler' effect? Well, ...I don't really know

...I noe he said "overuse" (he said it well) but fer me "ANY" copper roun the P/Us had a negative effect/affect on my sound.

...I jes lernt tew find the spot on stage where it waz least hearable and went there whence it got quiet and lernt tew hit that volume whence I needed quiet.

...Good stuff and thank yew all.








(deranged internet-based alter ego, with my own lexicon and all.)

Please visit my page

[dean]

This is so cool!! I just hope we don't have to take a mid-term exam on this. Thanks for all the great info, everyone

Dean

[Drak]

Here, I think I found what I was looking for, the Lawrence Aluminum quote...
And BTW, I'm not trying to prove anything to anyone, just offering information. This is fun stuff, just like playing Telecasters!
We all have choices, and that's the coolest thing to have is the right to choose whatever you want to do, whatever floats your boat is fine.

I dig traditional, vintage, unshielded Telecasters as much as I dig my own shielded pre-amped Tele builds, it's all good.

These posts came from this thread:
http://www.tdpri.com/forum/tele-tech...dge-plate.html

Now let’s talk about aluminum. While aluminum has some of the best acoustical properties it has, by far, the worst properties to use for the bridge plate. It’s like salt in a soup -- small quantities can perform miracles but too much will ruin your dinner. Aluminum has an extremely high eddy current potential and when placed under a pickup ( grounded or not grounded) can make a hum bucker hum like a single coil, or make a single coil as quiet as a hum bucker. This all depends on the thickness of the plate. At about ½” thickness your single coil will be as quiet as a hum bucker, but you also lose about 60% output and about the same amount of highs. Leo used a .015 aluminum plate under the pick guard of his 54 Strat to reduce some of the hum and the buzz and take a little bit of the edge from the pickup, resulting in a very musical, sweet tone.

Aluminum has some strange properties, and it’s the only commercially available metal I know of that can eliminate the buzz caused by light dimmers. An inch thick copper or brass shield cannot reduce the buzz caused by light dimmers but .003 thick aluminum foil can! This is known some thirty years and the reason why Belden introduced double shielded cable ( Copper braid plus aluminum foil). There is one problem for guitar cords -- the double shielding makes the cable too stiff . It helps quite a bit when you shield your guitar with copper and aluminum foil.

Try this one-- wire a single coil to a jack and plug it into your amp. Put the pickup on a table next to your amp. Take an aluminum pan from your kitchen and put it slowly on top of your single coil and watch the hum disappear.

Bill

GTO, some thirty years ago when Belden introduced double shielded wire(Copper braid plus aluminum foil) they wrote that copper provided a better shielding for RF noises but only aluminum could reduce EMI (Electro magnetic interference). Both interferences are caused by electro magnetic radiation. The only difference is the frequency range. Light is another form of electromagnetic radiation but at much higher frequencies. The ionosphere blocks the higher frequencies like ultraviolet, x-rays and cosmic rays and lets the lower frequencies of the visuable spectrum pass through. It’s also known that lead blocks x-rays. Like the ionosphere blocks the higher frequencies beyond the visuable spectrum, copper tape blocks the higher audio frequencies, like the buzz caused by monitors and fluorescent lights. Only humcanceling pickups, in combination with aluminum shielding, can reduce the interference caused by light dimmers.