Sunday, April 12, 2009

Don't bother Star Grounding your guitar (Buzz Kill?)


Every once in a while I get an email from someone asking me about the wonders of the Star Grounding wiring system featured on the GuitarNuts website. Now I like the Guitar Nuts site and there are loads of great information there but this one article is starting to drive me GuitarNuts. The original claim was that by adding shielding and removing ground loops from a guitar or bass equipped with single coil pickups you can drastically reduce hum and noise. But like any good myth the claim has been embellished by time and repetition. Now I'm getting emails from folks claiming that Star Grounding can totally remove all noise from single coil guitars and even help guitars with humbucking pickups. On the other side of the fence there are those who now claim that Shielding and Star Grounding your guitar is a "tone suck" that will harm your carefully crafted tone.
So, is this Shielding and Star Grounding practice worth while or is it just a lot of B.S. ?
Well, just like any good myth it has elements of truth and exaggeration. Let's start with shielding the guitar. Shielding is a conductive enclosure around one or more signal conductors ( pickups, pots, switches ect...), used to keep out electrostatic fields that can cause hum, buzz, or other noise. Shielding is often a good idea on many single coil guitars. Particularly Strat copies that often didn't come with much shielding to start with. A good practice for shielding a Strat type guitar is to use either copper foil tape or conductive paint to shield the pickup cavities and the control cavity including the back of the pick guard. Then this "Shield" is connected to the guitars ground. It's pretty simple and very effective at getting rid of noise. But it will never make your single coil pickups hum free. When folks tell me they have fallowed the Shielding and Star Grounding instructions on the web and noticed dramatic improvements, well, this is why. Shielding helps!
On the other hand trying to reduce noise by hunting down and removing "Ground Loops" inside the guitar via the Star Grounding method is a waste of time. Why? Well let's start by looking at what a ground loop really is. Ground loops are real and they can be noisy little buggers that occur when you can trace a loop in the ground connections between separate pieces of AC powered equipment in your signal chain. Hank Wallace wrote a great article about this over at Atlantic Quality Design. So why can't a guitar have a ground loop? To put it simply it's because a guitar only has one ground path. That being the cord. Because every component in a guitar or bass is grounded at the output jack it was already "Star Grounded" when you bought it. No matter how you wire the guitar all the grounds must converge at the output jack. So basically there is no way to wire it that isn't "Star Grounded". In fact the only way you can get a ground loop inside a guitar is to wire it up with two separate outputs that run to two separate amps and star grounding the wiring inside the guitar won't fix that either.
Some like to argue that the neck pickup lead might be longer then the bridge pickup lead causing a voltage drop that could create a ground loops. But there simply isn't enough wire or voltage inside a guitar to make this a reality. Want to test that assertion? Find a stock Fender Jazz Bass that has RWRP single coil pickups and is noise free with the volume on both pickups all the way up. Now open it up and measure the pickup leads. See? The neck pickup leads are much longer.
So, will shielding your single coil guitar or bass help reduce noise? Possibly. Will it kill the tone of your instrument? Not unless you wrapped your pickup coils in cooper foil. That can cause you to lose some of the high end.
Will Star Grounding your single coil guitar help reduce noise? Absolutely not! No way. It's a total waste of time and should be avoided. Am I being unclear? The problem is that most of the folks who attempt the Star Grounding system on a guitar or bass are electrical novices that might not be too skilled at avoiding cold solder joints or over heating pots or capacitors.So why trip them up by giving them a pointless project to fallow that just adds to the confusion?

Well, I guess that's it for now. Next time we'll tackle the "Aged Magnets" myth.

11 comments:

J. Mancine said...

GuitarNuts concept of star grounding as a mod to improve noise is silly. As you point out, joining the grounds on a central ring is no different electrically than them eventually joining at the output.

I will say that moving the entirety of the internal connections to a central point in a shielded cavity MIGHT help block some RFI and white noise...but doubtfully enough to measure.

So, I agree 99% that it is useless as a mod. But while I would never recommend "star grounding" as a mod to an existing circuit (the desoldering is more risk than benefit for most people), I wholeheartedly endorse central grounding for NEW circuit installs.

Bringing everything to a central grounding ring (as opposed to the pots themselves) does provide a more simple, neat and "clean" installation with less risk of damage to the components. Though I have done it dozens of times, I have never understood putting a shiny new pot in a guitar and then bending back the ground lead and soldering it and a bunch of wires to the body. It is a much more elegant solution to simply solder a wire between the ground electrode and the central ring.

Furthermore it provides a much better visual representation of the circuit and makes adding/removing individual components, and troubleshooting much simpler.

Clint Searcy said...

Well, I guess if I were working simply to improve the aesthetics of the control cavity I think I would start with PCB mounted components and solid copper wire that can be bent and placed with precision and would stay put. That would look nice.

bmmpinc said...

There is a new method of thinking within the idea of "star grounding" that has proven very beneificial to noise issues in guitars.

years ago Some engineer decided that "Ground" should be "everywhere" in a circuit thereby making it easy to wire only the "hot" signal.

but, by looking at the "ground" as another completely seperate signal and trying to "force" it to travel a specific path within the layout of the circuit, you can make any shielding in the circuit become more "active" so to speak.
this is not an easy concept to explain without showing it . so I will leave you with an example to ponder.

Imagine a strat with full shielding. connect all the pickup grounds to the back of the vol, pot as per "normal" .
now, without altering anything else in the circuit, move the output jacks ground wire from the pot back, to the sheilding on the floor of the cavity, and make sure that the guitar will only work when the guard is fully screwed in it's normal position...

your "forceing" the ground signal to flow through the sheilding to even get to the output jack. this mod alone can drop another 6Db in noise if done correctly.

and if you want a Strat to be completely silent. lift all the pickup grounds with a .005 Cap. this will give a notch filtering effect in the low mids. but it will leave your highs alone. and there wil be NO hum at all.

Anonymous said...

Interesting reading, but where does he say to quote you "in some cases totally eliminate hum" ?
He actually says "No shielding is 100% effective if you're using single-coil pickups"

Anonymous said...

He also says "The star-grounding presented here is important more for protection against white noise and radio interference than 60hz hum"

Clint Searcy said...

The claims that the star grounding system can totally remove all hum mostly come to me in the form of E-mails. I have edited the post to better reflect what I meant. Regardless of who is making the claim it's still false.

Start Grounding will not improve the sound or reduce the buzz of an already well grounded guitar.

Shielding can help reduce noise but there are far better products than aluminum foil to do it with and will not remove all noise from single coil instruments like Jazz Basses or Strats.

White noise and radio interference introduced at the guitar itself aren't really problems that plague today's guitar players. If your hearing a radio station over a guitar signal your likely dealing with a crap stomp box of watching "This Is Spinal Tap".

Thanks for readin!

PSR said...

So (correct me if I've got this wrong) you could shield a guitar, and attach all the grounds to the sheild- treating that as the common point?
Something like shield the jack cavity, and have a wire through to the body cavity and have the string ground by coating the trem cavity and some of the shielding to the body cavity (maybe under the pickguard by the trem?)

Clint Searcy said...

I don't recommend doing anything to your guitar if it doesn't have an unusual noise issue.

What kind of guitar do you have and what's wrong with it?

Chad said...

Clint,
Stumbled onto your blog while researching a particularly annoying issue with a Mexican strat I'm working on. Thought you might be able to help if you're so inclined. The pup config is HSS. In all but the absolute single coil positions the thing is pretty much silent. But turn on just the middle or neck pup and it sounds like an angry little man with a chainsaw is raising Hell in there. All the usual stuff to "quiet the beast" isn't working. I started with shielding the interior with aluminum foil. This had negligible results. I'm not sure it's any quieter than before that mod. When that didn't work, I proceeded to wrap the single coil pups with copper foil (I have not as yet grounded that foil to the interior shield. Next, I wrapped the conductors for both singles in aluminum foil. All of which failed to quiet those pups down. Out of desperation I tried a suggestion from one of your readers who said that running the ground wire from the output jack to the interior shield could drop the noise level down as much as 6 db. This also failed...miserably. Currently, I'm experimenting with a dummy coil to quiet down those singles. But so far I haven't had any success. I'm about to pull my hair out on this one. About the only thing which has silenced these pups is to completely roll off the tone controls. Of course, it's unacceptable to run it like that. I'm just stumped. Still, I press onward, though. Any ideas? Thanks

Chad said...

Clint,
I apologize if this is redundant. I just tried to comment and it looks like everything I just typed got lost.

Anyway, I'm working on a Mexican Strat HSS pup config. It refuses to shut the hell up. It runs very, very quiet in any of the humbucker modes, but as soon as you switch to a dedicated single, your ears are treated to "sweet" sounding chainsaw hum from the depths of Hell itself.

I've tried the following without success. Shielding the interior with aluminum foil. wrapping the singles in copper shielding tape (w/out connecting them to the interior shield), wrapping the single coil pup conductors in aluminum foil and connecting the output jack ground to the interior shield. Right now, I'm experimenting with a dummy coil set-up but so far the results aren't promising. Any ideas, suggestions? I'm starting to feel pretty desperate here. I've been modding these things for a couple of years, now, and never have I encountered an axe as stubborn as this. Thanks

radmin said...

If the bridge is grounded wouldn't your hands provide an alternate path to ground?