Is "Star" grounding really worth it?

[mrbrown49]

Hey All,

I have a 2002 ibanez artist that I have been using as a project guitar to learn various setup, maintenance, and modding techniques. Previous projects included putting in a set of p90s, and though they were fairly quiet, noise was an issue. So, the latest project involved gutting the electronics and shielding all the cavities with copper tape. Then, I replaced all the pots, and wired it up. For every point that needed a ground (pots, bridge, jack, switch etc.) I added a short patch of wire with a terminal on the end. All the terminals were then slipped onto a screw and they were all screwed into the same point in the body cavity. That gives me a "star" grounding configuration.

 

So, my question to all of you is, was all that extra effort worth it? It sure was a fun project, and it sounds great, but are ground loops really that big of an issue, and if so, how?

 

Thanks,

Scott

[ashasha]

If it was a single coil guitar that had hum then it may possibly be worth a try. If it is a humbucker guitar that didn't have hum issues then it was probably just some fun to learn how to do a star ground.

 

I don't buy into the whole star ground system inside a guitar most of the time anyway. It is a good system for things like studio equipment to avoid ground loops, but in that case you are talking about higher voltages generating the hum because it is using the signal connection between the equipment to ground the equipment rather than the power connection ground.

 

It is primarily a safety measure though. With a guitar you aren't talking about a piece of equipment that is plugged into a wall that has active electronics and voltage potential differences; you are talking about RF interference. Star grounding is good at eliminating differences in potential between equipment that could possibly shock you. It can reduce noise if there is enough current flowing through the device's signal path that it creates heat which can cause some distortion. Also if it is 60 cycle based noise it could cause hum, but that is easier to eliminate with proper source/destination grounding.

 

Plus if you measure the resistance between the original grounding point in most guitars which is at the back of a pot and then measure the resistance from there to the new star grounded spot it is going to be 0 ohms. Current flows to the path of least resistance; in this case the least resistance is exactly the same either way. If there was an isolation resistor or diode or even cap of some kind then perhaps there may be something that it could do.

 

The shielding will help with RF interference, but unless you have a guitar that has a balanced output and did source/destination grounding by lifting the ground at the source then star grounding isn't going to make a lot of difference. RF won't be bled off to ground if it is already in the signal path.

 

Only way to really do that is with common mode rejection which is only in balanced audio connections and this is assuming that you have a good clean signal to begin with. That isn't usually the case with single coils as that is the source of the sound and the noice simultaneously. If the noise is in there at the output of the pickup then it ain't coming out no matter how you ground it.

 

If star grounding really worked then companies like Fender would have taken the 2 extra minutes and 6 inches of extra wire to eliminate the hum years ago. Shielding and setting the pickup height as low as possible is probably the best bet to reduce hum.

[mrbrown49]

Thanks for the reply ashasha. Some good info there. I think the reason star grounding was recommended is because adding the shielding introduces a lot of redundant paths to ground that could cause hum issues, though i don't really know if thats true or not. To me electricity is still some sort of magic. I am trying to sort it out, but its an uphill climb.

[Mighty Coogna!]

Star grounding refers to multiple metal rods pounded into the ground to create a better ground for residential wiring.

 

I'm not sure where you picked up calling it that for guitar wiring. I've never seen or heard it called that before.

 

What you're essentially trying to do is create a faraday cage that encloses the guitars onboard electronics in a metallic mesh or foil.

 

I wouldn't worry about multiple ground points as long as they all link up. But hey, maybe someone else has other information.

 

Did a search, http://www.sweetwater.com/expert-center/glossary/t--StarGround

as you can see it's more for powered equipment.

[mielkea]

It seems to me to be a pretty common way to discuss guitar grounding to a central point. I've heard it plenty; that said, never tried it, so can't comment on OP question.

 

AM

 

 

 

Star grounding refers to multiple metal rods pounded into the ground to create a better ground for residential wiring. I'm not sure where you picked up calling it that for guitar wiring. I've never seen or heard it called that before. What you're essentially trying to do is create a faraday cage that encloses the guitars onboard electronics in a metallic mesh or foil. I wouldn't worry about multiple ground points as long as they all link up. But hey, maybe someone else has other information. Did a search, http://www.sweetwater.com/expert-center/glossary/t--StarGround as you can see it's more for powered equipment.

 

[Hanglow]

It's useful in effects pedals and amps especially. I think it's good practice to do it on whatever type of project you undertake. That said I haven't bothered to do it to my guitars

[headless]

 

... I'm not sure where you picked up calling it that for guitar wiring. I've never seen or heard it called that before...

 

 

I think I know one source of this terminology, in reference to guitar wiring:

 

http://www.guitarnuts.com/wiring/shielding/shield3.php

 

(just search the page for the word "star", it's in point #14, about half-way down)

 

Personally, I've never understood this grounding concept--but when it comes to electrons, I don't understand much.

[ashasha]

 

I think I know one source of this terminology, in reference to guitar wiring: http://www.guitarnuts.com/wiring/shielding/shield3.php (just search the page for the word "star", it's in point #14, about half-way down) Personally, I've never understood this grounding concept--but when it comes to electrons, I don't understand much.

Yeah, I've been to that site and there is some very useful information and yes, the star grounding procedure is 'technically' accurate, but not terribly useful.

 

Star grounding is for electrical power. The quit and dirty explanation is that we have grounded outlets because we don't want to be electricuted for touching an electrical device while we stand in something damp or are just touching something that has a less resistive path to ground. When we talk about this stuff we are usually referring to the potential differences between the chasis of the equipment and a common or preferably central earth ground. And that potential is usually a DC potential, that can hurt a lot.

 

So we eliminate that potential by grounding everything to a central point. In a true stargrounding system each piece of equipment has its own chasis ground and each grounding strap is the same length. This makes sure that the path of least resistance is its own grounding strap.

 

I was going to try to draw a picture of how all this crap works, but I am tired. So here is a scenario.

 

You are playing on stage, you've got your guitar and you are also singing into a mic. The amp is plugged in right behind you into a grounded outlet and everything is cool. The mic is plugged into the PA system that is about 100 feet away and isn't grounded to the same point as your guitar...hell lets say that it isn't grounded at all. So you get up there, fret a big fat power chord and get ready to sing, your lip touches the mic. So now because some jackass didn't disconnect the shield of the mic at the female end you just completed a circuit from the chasis of the mixer, through the mic cable, through the mic, through your lips, through your hand, through the guitar cable to the chasis of the amp, straight to ground. Bam, you are lucky if you just get the {censored} knocked out of you, let alone worrying about hum.

 

The correct way would have been to make sure that everything is on the same ground and to disconnect or 'lift' the mic cable's shield where you plug it into the mic (female end). So we have no ground loop because both pieces of equipment have their own path to ground and the mic cable won't provide a path to either chasis ground. The guitar on the other hand isn't a balanced device so the outer ring on the connector is usually attached to the chasis ground of the amp. If you lift that you break the entire circuit for sound.

 

You don't lose the sound with the mic because you have two signals that are 180 degrees out of phase with eachother. So at the destination it uses a differentiator circuit to amplify the differences between the two, which ends up cancelling anything that was in phase. In this case the only thing that would be in phase would be RF interference that the cable picked up between the source and destination.

 

So hopefully this explains why I don't think that the star ground is an effective technique for guitars. Shielding on the other hand, huge and very effective.

[MahaloVision]

Star grounding is a much bigger deal with amps, not so much with traditional guitar electronics.

 

One thing you can do to help minimize the effect of getting shocked is to wire a small resistor and capacitor in parallel on your wire to the bridge (assuming you're using a passive pickup set). You can still get shocked, but not as badly.

[GibsonQC]

 

So now because some jackass didn't disconnect the shield of the mic at the female end you just completed a circuit from the chasis of the mixer, through the mic cable, through the mic, through your lips, through your hand, through the guitar cable to the chasis of the amp, straight to ground. Bam, you are lucky if you just get the {censored} knocked out of you, let alone worrying about hum.

 

 

 

Isn't there a way to wire a resistor between the bridge ground wire on the guitar and the electronics to prevent you from getting killed in this scenario? I can't remember where to find it, but since I rewire my guitars weekly, this may be a useful mod to do next time I rewire....

[GibsonQC]

 

Star grounding is a much bigger deal with amps, not so much with traditional guitar electronics. One thing you can do to help minimize the effect of getting shocked is to wire a small resistor and capacitor in parallel on your wire to the bridge (assuming you're using a passive pickup set). You can still get shocked, but not as badly.

 

 

 

Yeah, that's what I was thinking of. Is there a link showing how and what value resistor/cap to use?

[caveman]

 

Isn't there a way to wire a resistor between the bridge ground wire on the guitar and the electronics to prevent you from getting killed in this scenario? I can't remember where to find it, but since I rewire my guitars weekly, this may be a useful mod to do next time I rewire....

 

 

I believe guitarnuts has that also.