Guitar buzz - airborne EMI

[2pulse]

Apocalyptic airborne EMI buzz in my studio that even humbuckers can't buck. Single coils are murder. Every amp, every guitar. This happens on city power as well as with a battery powered amp with *every* circuit in my building switched off (take note, all of you fluorescent / dimmer / LCD monitor / groundloop / fan / wallwart suggesters). The buzz goes up and down with the guitar volume knob.

Rotating the guitar helps: there's a general direction you can point it that diminishes the buzz, but even that is unacceptably loud.

Here's what gives me hope: when I hold an omelette pan over the pickups, the buzz dies down a LOT. I'm not sure what type of metal the pan is, but it makes delicious omelettes, if that's of any help.

So I'm thinking "man-sized faraday cage". What is the most effective metal? Would it need to surround the guitar player on all sides or could it be a single wall between the guitar and the EMI source, as the pan experiment would suggest? Has anyone ever pulled this off?

I guess the other option would be to move. Help keep me from doing that!

[Kiwi]

I have a similar problem in my location. It varies with load on the grid - so there are times when everything is quiet as a baby church mouse sleeping. Then all hell breaks loose again.

I use a Pignose amp with a cheap single coil pickup on a short cable as a hum detector. Can't blame ground loops or AC heater hum or anything on a battery powered solid state amp. Yep - it's airborne EMI. Sucks arse.

Solutions? Get a decent laptop & interface for mobile tracking of guitars, and just get the hell outta there ...

Or EMG pickups. They really work - but some models have better noise rejection than the ordinary EMG pups fitted to stock guitars. If building a studio guitar for that environment, that's a trade-off between tone and noise.

Or Line6 Variax guitars: the piezo pup is immune from hum, and the digital electronics turn that into fairly reasonable clones of various electric guitars. Another trade off between tone and noise. And i've found the electronics to be a bit hissy - although I haven't tried the latest models.

OR - a Faraday cage as you suggest. Many times I have contemplated building one.

Do you have room on your property for a shipping container? That would be the easiest way to get a pre-built faraday cage. Fit it out with breathing air and lights and carpet, and I think that would make a good space for tracking guitars.

Technically, I think the noise you are getting may be electrostatic buzz rather than electromagnetic hum. Electromagnetic fields are hard to stop than electrostatic. The fact that the aluminum pan shielded it is good news. Aluminium can't stop magnetic fields - you need steel for that. What I think was happening is that the pan was connected to earth via your body, and provided the shielding you need.

Get a roll of aluminum foil, and cover some cardboard boxes and see if this is all you need. Connect the foil electrically to ground. You might be lucky - and if this is the case, some cheap expanded aluminum mesh might make some gobos that do the trick. Always connect them to ground/earth.

You can acheive a lot by grounding/earthing your own body - which then becomes a shield rather than a conductor. A ground spike in the earth outside your studio - run a wire into the studio and use this as a safe ground to your body. Run a wire into your sock ...

Good luck

[Ry-Fi]

I'm hardly a guitar pro, but it sounds like an issue with your guitar's control cavity being poorly or not-at-all shielded.

I have a decent low end Yamaha that drove me pretty nuts with its noise. There was nothing wrong with its wiring, so I figured it was the lack of shielding, of which there was none. I spent about an hour and $0 fixing it. I took the pots & switch out, covered the inside with plain kitchen aluminum foil (using double-sided tape), and then put the controls back in, making sure nothing was touching the foil except for the bodies of the pots (already a grounding location). I made the foil overlap where the cover goes on, and treated the cover with the foil too. I put the cover back on, and voila! WAY less noise! Drastic improvement.

You can use other materials: copper foil, conductive tape, conductive paint, etc., but many people report great success from simple aluminum foil.

It's definitely worth a try!

Also, it could be a problem with the wiring too. Not sure if you're capable of diagnosing and repairing that kind of stuff or not... (basic DIY electronics/soldering skills are a valuable asset!)

If you have a grounding problem it could be responsible for crazy noise. Look for wires that have become broken or detached, a pot lead touching a wire it's not supposed to be, bare wires touching where they shouldn't be, etc.

Another possible cause is if your signal wires between pots and switches aren't shielded. The signal wires should be shielded and the shields patched into the grounding scheme. The ones from the pickups rarely are, but everything else should be if possible.

Hope some of this helps!

[Kiwi]

FWIW - this is something i found on the net and have blatantly ripped off:

Originally Posted by unidentified legen

On Dec 24, 8:55 pm, Dave Curtis <dbaudiot...@roderunner.com> wrote:

> >The tele article is pretty much how one should shield an instrument.
> >You want copper foil and spray-on glue (artist type works well) so it
> >sticks in place in the cavity. Heavy foil is harder to mash into place
> >but it works just as well. The basic idea of shielding is to enclose
> >ALL parts in a closed metal box.
> "Faraday cage" is the technical term.



Except "box" is a better term. If you use open mesh for shielding
(like say copper window screen) it can be less than 100% effective.

> > So you need copper all over the
> >cavities and metal (usually the knob-plate) as a cover. If a cover is
> >plastic (like say a back battery plate) you need to stick a copper
> >sheet to that too.
> Well, no, you don't. (see below)



Well, yes you DO! (see below!)

> >It should be clear that you really can't cover the
> >TOPS of the pickups with foil.
> You *could*. It won't affect the magnetic field.



Depends. Some pickups do have total shielding, but usually the pole
pieces stick out through the metal (Les Paul is an example) Tone can
be effected and looks definitely are! So usually we don't and I've
never seen it really needed anyway.

> > So that should be the ONLY openings in
> >your copper shield "box". Hum that gets in that way should be minimal.
> >Don't forget that the wires from the pickups to the cavity need to be
> >inside the shield too! If they go through holes you'll need to make
> >some foil tubes to put them through. All this is very much WTH!
> Pickup cables are usually shielded anyway.



Some are and some aren't!!! The smart money checks YOUR pickups to
see which you have. If they are shielded you don't need to do more. If
they are ordinary wires, copper tubes are called for. (Copper braid
can work here too)

> >Note that you really don't want any wires, circuit boards or other
> >connections touching the foil. If it looks like something is going to
> >be close use some paper or tape (as someone already said) to make sure
> >the parts can't short out on the shield (which is always ground). By
> >the way the battery needs to be inside the shield too although on many
> >basses it isn't!
> No, the battery doesn't need to be shielded. It's a DC power source,
> and carries no signal.



Correct and yet wrong! It's a subtle thing but hum introduced from the
battery depends upon a number of things. One is the internal impedance
of the battery. That rises as the battery gets used up. And even worse
the battery can act as a nice antenna picking up Radio frequency
interference (RFI). This can reek havoc in a bass. G&Ls are seriously
known for this. The only true shield is a TOTALLY enclosed copper
box! Note that if there is even small cracks or holes RFI can creep
in. Also be aware that RFI is NOT the same "hum" your bass normally
picks up. That hum comes from capacitive coupling to power lines and
cords. Your body makes a great antenna to pick up that kind of hum
which is why when you "ground it out" by touching the strings, the hum
goes down!

> >> Also, I have not installed any of the parts yet. Don't know if the Audere
> >> will hum or not. The stock config hums quite a bit if I'm not touching any
> >> metal.
> That's not abnormal. Shielding won't help that much.



Bzzzt. Wrong. This is EXACTLY what copper shielding is there to
eliminate!!! When the bass is shielded you should find ZERO difference
in noise level when you touch the bass (ground) or not. If that is
true then your electrostatic hum shielding is good!

> >But since I bought all this copper foil and stuff, figured I might as
> >> well do it all up.
> Unless your copper has conductive adhesive (like Stew-Mac's) you need
> to solder all the individual pieces together that line the cavity.



Yes, this is what I always do. People praise the conductive glue, but
I worry about it. I know the solder won't dry out and come loose years
later. If you are the kind of guy who sells one bass to buy the next
bass then it doesn't matter.

> >Note that there are TWO kinds of hum. There is electrostatic hum and
> >magnetic hum. Electrostatic hum is the kind that the copper shield
> >will stop.
> That's RFI.



That's wrong. There are THREE kinds of "noise" which may or may not be
"hum". The first I call "electrostatic hum" This is a capacitive
coupling to the high voltage in AC power lines. A copper box stops
that cold. The second type of hum comes from magnetic fields. These
are produced by power transformers, ballasts and the like. The fields
go right into the pickups like the signals from string motion. The
way to get rid of these is by using TWO coils out of phase, but with
the magnets reversed in one so the string signals are IN phase! These
are called "humbucker" pickups. A G&L has these as do Stingrays and
many other basses. You can even do the same thing with two separate
pickups like the two pickups on a Jazz. This is why if you have both
pickups set to the same volume the hum goes away. The pickups are
actually wired as "humbuckers". This hum is sensitive to the
orientation of the bass with respect to the magnetic source. It is NOT
sensitive to touching any strings or grounds!!!

And lastly there is RFI noise. This is high frequency noise often from
radio stations and the like. It crawls into a preamp and mixes with
signals in there. Sometimes you actually can hear the radio station
playing and other times it just creates hum or noise! This is by FAR
the biggest pain to get out of there. Often tiny "bypass" capacitors
have to soldered across signal leads to shunt the RF to ground. A
tight copper box does wonders as well. Sometimes you need BOTH!
Getting the RFI noise out of a G&L bass is a MAJOR technical pain!

> >You can usually tell if you have that because the hum
> >levels change as you touch strings or bridge or wires etc.
> No. I don't care how well shielded it is, if they're single-coils,
> it'll hum when you're not touching the strings.


Sometimes true. That is because it is picking up MAGNETIC hum.
However, it will ALSO hum if you ARE touching the strings!
If the hum level changes as you touch the strings it means the bass
NEEDS more copper shielding! Period.

> >The other
> >hum is MAGNETIC hum which is picked up by the pickups from AC
> >transformers and the like. You can tell if you have this hum because
> >it will change with the orientation of the instrument, but won't
> >change if you touch it. You may even find a position of the bass that
> >nulls it out!
> That's RFI, too.



Not so. The fact that you can find a null orientation of the bass says
that you are picking up stray AC magnetic fields. RFI can also cause
hum (and noise) but tends to crawl all over everything and hence
doesn't usually null out with instrument orientation. The Samarium
Cobalt pickups go a long ways toward reducing magnetic pickup without
resorting to humbucker pickups.

> >You are VERY MUCH on the right track with samarium
> >Cobalt pickups which by reason of increased magnet strength are very
> >much less sensitive to magnetic type hum even in single coils! Dual
> >coil "humbucker" pickups are designed to eliminate magnetic hum, but
> >the two coils does give a different tone than single coils.
> Humbuckers *cancel* the inherent hum (RFI) in single coils.



Humbuckers use two coils to cancel the large magnetic field (assumed
to be pretty much constant over the two coils) They are designed to
NOT cancel the signals from the magnets and strings. However the fact
that you have two coils DOES change the tone. Tends to make it more
fuzzy and less "pure".

> It's all called RFI or Radio Frequency Interference, and it's not just
> hum.


Not RFI! It's magnetic fields. Try moving your bass pickups near the
power transformer in your amp. Magnetic leakage in that transformer is
easily picked up by the bass. It's NOT RFI and it's NOT capacitive (I
called that "electrostatic") pickup.

> Electrostatic and Magnetic Hum? I've never run across those terms
> before.


Well, I sort of made them up, but they are more or less descriptive of
what is going on. Technically you have electric fields (created by
charges) and magnetic fields (created by currents) BOTH cause hum in
basses! And in active basses RFI crawls in and causes hum and noise
as well! Passive basses don't have as much RFI problem because the
bass cable tends to short out the RFI. And amps tend to be better
designed to deal with RFI and finally the RFI can only cause problems
in a badly designed amp and can't do anything in a passive bass.
However, there ARE some amps that will "play radio stations" on
occasion!

> >Bottom line is that you are doing good! install a nice copper shield
> >over as much as you can. Make sure nothing can short out. and with the
> >S-C pickups that should end up one totally hum-free mean machine!


My experience is that shielding is almost always worth the effort. And
if it really isn't needed (sometimes a bass doesn't hum even though
there is next to no shielding, still putting it in always gives me the
"warm fuzzies" since you just never know when a gig will be next to a
radio station, have gigantic lighting transformers on stage or power
cords run all over the place. When you get to one of those places
you'll be glad you took time to shield your bass.
Benj

[Kiwi]

I think it's a crime that in 2011, guitars are still made so poorly.

The advantage of a faraday cage would be you could record any stock guitar without resorting to a massive rebuild job. Even expensive Gibsons can have completely useless shielding. WTF? Lazy SOBs.

I propose that some brave guitar maker introduce a new standard method of construction that puts the pups and all electronics into a metal box. Guitars should be 100% shielded right from the get go. None of this "conductive paint" bullshit. No unshielded wire (unless inside the box). But seriously - the whole lot could be in a metal box, that could be fitted into any shape of guitar.

The time is right for somebody (hint: Line6) to redefine electric guitars. It's 2011 - we need to be wireless right from the start. Put the pups and controls in a shielded box, and get the pure tone direct to wireless. Digital wireless is the obvious solution, so make the A/D damn good right in the guitar. Total immunity from hum and buzz, with wireless freedom on stage and studio.

A well designed system that allows ANY type of pickup to be fitted (I suggest a rail system) could create a golden age of electric guitar design. And more important, and return to pure tone.

I can dream.

[Ry-Fi]

2pulse, got anything to reply? We'd like to help you get rid of your noise problem.

[2pulse]

Big thanks for the replies! Haven't had a chance to do any more tests/troubleshooting since my OP.

Shielding of the electronics cavity is good advice, but not something I can do to most guitars that clients drag in here, hence the Faraday cage being an attractive idea.

As for the mobile rig suggestion, that's exactly what I've resorted to doing on occasion!

[allphourus]

Originally Posted by Kiwi

You can acheive a lot by grounding/earthing your own body - which then becomes a shield rather than a conductor. A ground spike in the earth outside your studio - run a wire into the studio and use this as a safe ground to your body. Run a wire into your sock ...

Good luck

I think that this is possibly the worst suggestion I have read here on any subject. Putting an earth ground in your sock is going to set you up to be Dead. It might help your noise problem but touch anything else in in your studio that is not properly grounded, or has an electrical fault or is failing catastrophically And the current will pass through your body to ground, and particularly with your left hand arm right across your heart and electrocute yourself. When working with high voltages electricians and service techs have a saying "left arm behind your back" so you don't inadvertently ground your self and do just that, kill yourself. tutt