Let's talk about single coil equipped guitars shielding

[ErikH]

Re: Let's talk about single coil equipped guitars shielding

from a recent post this morning ... this explains it very well. Thanks the MARVAR ... excellent link.

http://www.taylorguitars.com/see-hear/Video.aspx?file=AudioGrounding_High.wmx

Thanks for that, doveman (and marvar). That's a cool video. Everybody should watch that.

Gosh, I think I just heard him say the shielding is used as a filter to send the noises (RF and such) to ground.

Electric guitar circuitry may be AC, although very very small AC, but the "ground" side of the output jack is connected to ground through the ground lug of the input jack on the amp.

Yes, you need to clean up the wiring and make sure your gear is connected to earth ground, but the shielding the guitar will help keep things quiet as well by doing just as they gentleman in the video said, filtering out unwanted noises and sending them to ground.

 

[doveman]

Re: Let's talk about single coil equipped guitars shielding

Gosh, I think I just heard him say the shielding is used as a filter to send the noises (RF and such) to ground.

Electric guitar circuitry may be AC, although very very small AC, but the "ground" side of the output jack is connected to ground through the ground lug of the input jack on the amp.

Yes, you need to clean up the wiring and make sure your gear is connected to earth ground, but the shielding the guitar will help keep things quiet as well by doing just as they gentleman in the video said, filtering out unwanted noises and sending them to ground.

You are and were correct ...

Thanks should go to MARVAR ... who posted this this morning ...

Also ... the best thing I've done recently is get rid of my CRT computer screen and get a flat screen monitor ... Best Buy $185 ... recording is so much nicer.

:8:

 

[ErikH]

Re: Let's talk about single coil equipped guitars shielding

You are and were correct ...

Thanks should go to MARVAR ... who posted this this morning ...

Also ... the best thing I've done recently is get rid of my CRT computer screen and get a flat screen monitor ... Best Buy $185 ... recording is so much nicer.

:8:

Thanks for the backup.

Yeah, I agree on the CRT screens. Ever since I got a flat screen the noise level has decreased a lot in this room, which is where I practice and record too.

 

[uOpt]

Re: Let's talk about single coil equipped guitars shielding

Thanks for that, doveman (and marvar). That's a cool video. Everybody should watch that.

Gosh, I think I just heard him say the shielding is used as a filter to send the noises (RF and such) to ground.

Electric guitar circuitry may be AC, although very very small AC, but the "ground" side of the output jack is connected to ground through the ground lug of the input jack on the amp.

Yes, you need to clean up the wiring and make sure your gear is connected to earth ground, but the shielding the guitar will help keep things quiet as well by doing just as they gentleman in the video said, filtering out unwanted noises and sending them to ground.

Going to a differential cabling system (two wires plus one shield) like microphones use is generally not required or even useful for guitar. The differential setup only eliminates noise that originates during the travel in the cable. While it would do so both for guitar and microphone, the guitar has a much higher basic output level than a microphone and the noise coming in via a properly shielded cable is negligible.

The problem we are trying to fix here is noise that originates in the guitar and is already in the signal when it enters the (potentially differential) cable. The differential cable won't help against that at all.

Now, you could enter a differential system directly out of the pickup through an unshielded cavity into a differential amp input, but that's not going to do much good. The shielding with kitchen aluminium foil is doing the job fine and you also have to wire the controls on the guitar. You need the shielding around the controls anyway.

BTW, it is not true that a guitar like a Strat that only has a shield on the pickguard (which means the front of the cavity). It has a shield on the back, too. You. Your body is used an a shield, by putting ground onto the strings and using you for shielding. That's why the noise goes up when you go hands free. This is a bogus setup, first of all the sides of the cavity are unshielded, and second it's dangerous. If you end up with a defective A/C amp cable that put a live wire onto the ground of your amp, you have 115/230 Volts on the strings. This is another reason why I always shield the cavity and then disconnect the strings from ground.

 

[doveman]

Re: Let's talk about single coil equipped guitars shielding

Who's saying use differential cable?

Disconnect the strings from ground? It must not be too dangerous since every guitar on the planet is wired that way. If the guitar is grounded to the ground prong as the video says, the ground to the strings should not be a problem.

I shield the sides of the cavity too ... then connect the shielding to ground, as well.

 

[uOpt]

Re: Let's talk about single coil equipped guitars shielding

Disconnect the strings from ground? It must not be too dangerous since every guitar on the planet is wired that way. If the guitar is grounded to the ground prong as the video says, the ground to the strings should not be a problem.

In a correctly set up amp it is not, with properly set A/C connector. The ground connection in a A/C connector should break last, so a loose hot wire touching it will just trigger the fuse.

However, if the ground connection breaks first in the A/C plug and touches a hot wire, then you have the full 115/230V A/C on the strings. This is very dangerous as your muscles cramp on an electric shock and your left hand will likely cramp around the neck so that the connection isn't broken even when you fall.

Since it is not necessary to connect the strings to ground if you have proper shielding inside the guitar it is an unnecessary risk.

Now, I know that some "experts" say that the strings should be grounded for safety, but that is only a benefit if you do something like stick the string ends on the neckplate into an A/C outlet. And these experts assume that all amps have their A/C plugs properly wired. The latter often isn't the case, in particular on vintage amps that people messed with. In practice the risk of the amp sending A/C to it's own ground is much higher than you sticking your guitar into an outlet.

 

[doveman]

Re: Let's talk about single coil equipped guitars shielding

So why would all of the guitar makers continue to make this error ... if this is the case? Wouldn't product liability cases have long ago ended this practice due to the electrocution of so many guitarists?

Free market usually takes care of this kind of stuff & the electric guitar has been around a while. For example: Old amps used to have reversable ground switch but that was changed a few years ago ... why not this too?

Still doesn't add up to me ... but then again it doesn't have to. :1:

 

[JB_From_Hell]

Re: Let's talk about single coil equipped guitars shielding

Doesn't your body act as the ground?

 

[uOpt]

Re: Let's talk about single coil equipped guitars shielding

So why would all of the guitar makers continue to make this error ... if this is the case? Wouldn't product liability cases have long ago ended this practice due to the electrocution of so many guitarists?

If somebody gets injured from this, the fault is formally with the amplifier. It is the amplifier which put a hot wire onto the grounded surfaces and hence caused the malfunction.

For almost all electric devices it is standard practice to ground all exposed metallic surfaces. This is done so that if a hot wire inside the device becomes loose and touches one of these surfaces the fuse triggers. That means the fuse is blows right on the wire fault, while hopefully nobody is currently touching the surface, or even if somebody touches it then it's only a short shock until the fuse triggers. Guitar makers just do the same thing by default.

This doesn't make sense in a guitar since there are no hot A/C wires anywhere inside the guitar (unless you got the active pickup thing wrong ), the only way where the grounded strings protect you is, as I mentioned, if you stick your guitar head into an A/C outlet.

In addition, people don't mess with their microwaves. The above schema assumes that the basic wiring is correct, namely that the ground wire is the last thing to become deattached. This is certainly the case for all microwaves that you pick up in Wal-Mart today. So hot wires don't touch your surface. But it might not be the case for your 30 year old amp that non-electricians modified, that has been transported often and that has a 30 year old power cord. The risk that your new microwave puts a hot wire onto grounded surfaces is almost zero. The same is not the case for beaten up amps.

Last but not least you have the guitar hung around your body, and your left hand is already around the neck. If you get a shock this way the cramping will ensure that you'll be electrocuted until either your body triggers the fuse or somebody cuts the power (hopefully not by trying to rip the guitar out of your hands).

JB_From_Hell, there is too much resistance to the ground. It's enough to transport a 115 V electric shock, but not enough to let the signal levels through that you need for shielding. That's why the hum suppression through the grounded strings works.

 

[doveman]

Re: Let's talk about single coil equipped guitars shielding

If somebody gets injured from this, the fault is formally with the amplifier.

So it would be Fender's fault ... wait a minute :scratchch I think a good lawyer ... maybe even a bad one ... could have made that "fit for use" connection.

But that's OK ... you make some good points to consider ... you make a good argument.

I guess your point is that if I ground the cavity on my Tele, I can disconnect the ground to the strings (which I have admittedly not tried). Of course I've still got to touch the control panel ... I wonder how I could deal with that? The guitar nuts site mentions a "electocution mod" that might be an alternative for both ... but I never considered it. But they also peddle the "star ground" which appears to be a myth (that I have tried). Doesn't hurt but doesn't help either.

Something to consider I guess ... but it must be pretty low risk ... I've been playing since the 60s and I've never heard of anyone suggest this particular guitar mod ... disconnecting the ground wire to the strings.

Much more could probably be gained in general (practical) just following the video I posted.

Thanks for the info.

:cool2: