hardware

Bridge Ground and Mystery Ground Issues

It was a pretty noisy guitar.

There was a nasty hum that didn’t quieten down when I touched the strings. This is generally a good indicator that there’s grounding problem.

The quick test: Touching the metal of the jack on the (plugged in) cable quietened things. This means that somewhere inside the guitar, we’ve got a disconnected ground wire—if everything were working properly, there would be a signal path from the strings to the ground of the output jack.

A quick primer/reminder: The ground wires in a guitar help to ‘shield’ it from unwanted interference from the environment. The exposed metal parts of a guitar or bass are generally all wired to a common point. This includes the strings. Inside the guitar, there’s usually a wire from the bridge or tailpiece that runs to ground.

When you touch the strings (which you would normally do when you’re playing), you ground yourself through the guitar’s wiring and so you cease being a big meat-antenna, picking up interference, which is then picked up by your pickups.

Because this guitar quietened when I touched the output jack but not the strings, I knew that the path to ground had been interrupted somewhere.

Fixing the Bridge Ground

A quick look inside revealed what seemed to be the problem (more in a minute). I could see a wire from the back of a pot (common ground point) disappearing into a hole that pointed towards the guitar tailpiece stud. A gentle tug on this gave no resistance, however, and the wire pulled right out.

Problem found. Have to run a new ground wire to that stud.

Removing the stud bushing from the body isn't too much hassle (but be careful if you ever have to do this yourself). I fished in a new wire, stripped it back so it contacted the metal of the stud-bushing and reinserted the bushing. Then, I soldered the other end to the ground point on the back of the pot.

A quick check with my continuity tester showed that all was well—good connection between the bushing and ground—so I strung up and plugged in and…

Exactly the same problem.

What the heck? I was all set to treat myself to a nice cup of tea. What’s going on?

I pulled out my multi meter again and, sure enough there was no ‘continuity’ between the strings and ground (that ‘I’ on the meter indicates there is—for all intents and purposes—Infinite resistance).

NOTE: In case you’d like some basics on conductivity and resistance.

No 'path' between the strings and the ground point

Fixing the Ground ’Continuity’ Problem

I had a suspicion of the issue so I decided to work my way back with the meter.

The internals all looked fine. Perfect continuity between the output jack’s ground and the pot with the bridge ground wire. From outside, I could just probe the bushing and that was fine too.

Then the trail went dead. Suspicions growing.

This particular guitar has a black powder-coating finish on the metal hardware. I have a feeling that this coating is preventing a good ‘connection’ between the metal parts. Check on the conductivity/resistance article for more on this. Without a good connection, there is no ‘signal path’ from the strings to ground.

Remove the strings again. Time for some ‘scraping’.

What I’m trying to do is to get a sound, ‘metal-to-metal’ connection for the bushing, stud, tailpiece and strings. Working in the parts that won’t show, I remove some of the powder coating. I use sandpaper or just scrape if it’s easier.

I want to see some shiny metal on the threads of the stud and the internal ‘post’ that holds the tailpiece. Same on the slot in the tailpiece (you can see the difference in the photos below)

Removing coating from the tailpiece stud threads and post

The post recess is coated too. It's gotta go.

The coating is cleared and bare metal is exposed. Great.

Lastly, and most fiddly, I scraped a little coating off the holes where the string ball-ends contact the tailpiece.

String things up again and check with the meter… 0.00Ω. That means there’s a clear path with no resistance from strings to ground.

All good. No resistance means a perfect path to ground from the strings.

Plugging in reveals a much quieter guitar. Splendid. 

Guitar Hardware School: Frets III - Zero Frets

Back to school time.

Is it a fret or should we consider it a nut? 

It's a fret. But it does the job of a nut. Sort of. Just to round off the sections on nuts and frets, let's have a chat about…

Zero Frets

In some guitars and basses, a zero fret is installed. The zero fret sits where the nut would have been and the nut itself gets shifted, slightly, towards the headstock. The zero fret takes over the job of being the 'bearing point'. More or less by default, it handles the job of setting string height while the nut's job is relegated to just controlling side-to-side spacing. 

UPDATE: 

Just to (try) clear up confusion I may have caused, moving the nut, in this case, isn't the same as what might happen with a Buzz Feiten or another compensated nut. The zero fret sits at the same place a regular nut would have been. Since the strings sit on that zero fret, compensation is unaffected. On a zero-fret guitar, the nut gets moved towards the headstock and it's job is now to align the strings before they pass over that zero fret. Clear as mud? Please feel free to shout up in the comments if I haven't explained this well. 

Why would I want a Zero Fret?

Zero fret on guitar (note: the nut here is a 'captive' nut and holds the strings in holes rather than slots—this is relatively unusual and for a particular application)

Well, there is a pretty good argument around tonal consistency. Consider that most of the notes you play on your guitar have the string bearing against a metal fret as it sounds. On an instrument with a conventional nut, the open note doesn't bear against a fret but against one of those materials we've talked about before. Even with a great nut, that certainly has the potential to produce a slightly different tone. 

From a luthier's point of view, a zero fret makes for a perfect setup as it pretty much takes care of itself for string height. No mucking about, trying to file nut-slots until they're the right height for optimal playability and intonation—just level all the frets and there you go. The nut part behind the zero fret doesn't need the same finicky height adjustment. 

It's worth calling attention to a weird perception that zero frets are a mark of a cheap instrument. That's not the case at all. A number of cheap (and awful) instruments from the distant past had zero frets but that's not what made those instruments awful. 

If your guitar or bass has a zero fret, you can disregard the worry about nut-materials and tone and just get on with things.

Bottom Line: Is It Worth Upgrading?

Hmmm. It's not really something that people worry about. While it's technically possible (with some caveats) to move from a regular nut to a zero fret or vice-versa, I'm not aware of anyone feeling strongly enough to want to do so. I wouldn't loose sleep about it.


If you've found this useful, you can check out others in the same series of Guitar Hardware School. Feel free to share these on and shout up in the comments if you've questions. 

Guitar Hardware School: Introduction

Understanding the basic workings of various bits of your guitar—and the effect they have on playability and tone—can be useful. It can give you an appreciation of an instrument's limitations and can inform when you're considering any upgrades. 

With this in mind, I thought it might be useful to take a look at some of the individual elements of a guitar and delve a little into the reasons they're there and the reasons they are the way they are. 

So, over the next while, I'm going to do a series of Guitar Hardware School articles looking a little more closely at some of your guitar's bits. Some of these are probably going to be pretty 'deep dives' so be warned: It's gonna get geeky. 

Guitar Hardware

Guitar Hardware