buzzing grounding issue (I think I now understand!!)

[chrisanthony1211]

Got an old 71 Jazz bass that buzzes when I’m not touching the strings, not terrible but enough to annoy me, can someone explain in idiot proof language how to make sure this thing is grounded property, simple enough so that a Luddite could grasp....

Edited December 17, 2017 by chrisanthony1211

[chrisanthony1211]

Just read this in “no treble” is this correct? so this is a shielding issue not a grounding issue, I always thought buzz stopping when you touch the strings was grounding problem!!

 

• If your bass hums once you touch the strings (but is otherwise quiet), you have a grounding issue.
• If your instrument hums but becomes quiet once you touch the strings, you have a shielding issue.

[gary mac]

Sounds like a grounding issue. Worth checking amp and cables though. Assuming it's not a cable problem or a problem with the electrics in your house, then carefully inspect all the pots, output socket and ground cables, look closely at the solder joints.

 

[Dan Dare]

Single coil p/us, such as those on J basses, particularly older ones, do tend to buzz. You can reduce it, but you cannot eliminate it entirely in my experience. Shielding and grounding help, but single coils are very susceptible to rfi, fluorescent lights, etc, etc. I've shielded the pickup and control plate cavities on my 72 Jazz with copper film and grounded the bridge, but it still buzzes slightly, especially in some environments. Incidentally, it's worth using a small capacitor in series with the grounding wire for the bridge, so that if you get an amp fault and/or the earth to your equipment isn't working, you are at less risk of shock.

[gary mac]

I've seen the cap recommendation as a safety aid before but personally would not put faith in it. Only a fast blowing fuse could be relied upon. I think Taylor might be one of the manufacturers who do just that and install a fuse.

[chrisanthony1211]

10 hours ago, gary mac said:

Sounds like a grounding issue. Worth checking amp and cables though. Assuming it's not a cable problem or a problem with the electrics in your house, then carefully inspect all the pots, output socket and ground cables, look closely at the solder joints.

 

There’s quite a bit of conflicting information on the net, however from what I’ve been reading if you touch the strings and the buzz stops that shows that the bass is grounded correctly and the issue is with the shielding? 

However , If you touch the strings and it starts to buzz, then that’s a grounding issue, is this correct?

[chrisanthony1211]

The below I found on the net seems to make sense to me, how could I possibly be grounding the bass when I touch the strings when I'm not grounded myself!!!!

 

"And how, pray tell, are you grounding the guitar? Are you standing barefoot on a metal plate? Or touching a water pipe, perhaps?

Your body acts as a shield, and the guitar is grounding you.

Your body, on account of being much larger than the wiring inside the guitar, picks up noise much better. When you're simply holding the guitar without touching any grounded metal parts, you simply radiate any noise you pick up right into the guitar's wiring. Hence the noise. As soon as you touch a grounded metal part on the guitar (such as the strings), you're grounded through said metal part, and the noise will disappear, as it's being shorted to ground. This is why shielding the guitar should help, as it'll provide a permanent, always-grounded layer of protection between the noise and the guitar's circuitry.

Here's a couple of fun experiments to try. Plug your guitar into your amp and turn it up. Don't touch any metal parts. Unless your guitar is well shielded, you should hear some noise. Now place your hand over any of the pickups, while still avoiding the strings. The noise should increase. Try moving your hand closer to, say, a computer monitor. The noise should increase even more. Now put the guitar away from your body (while it's still plugged in). The noise should decrease. This shows how your body is acting as a channel for noise. And unless there's another shield in place between you and the guitar, you'll have to ground yourself through the guitar to avoid bleeding that noise into the circuitry.

Also, when you touch the strings and the hum increases, it's a sign that the bridge (and hence the strings) isn't grounded. The reason is that you're inserting the noise into the strings, which in turn concentrate it right above the pickups (which are extremely effective antennae), rather than sending it to ground via the bridge."

[chrisanthony1211]

It's true, I just tried the experiment he suggested, turn the amp right up and move away and no hum, the closer I get the guitar starts to hum, pick it up even more hum, touch the strings or any other metal grounded part and it goes away (the bass grounded me!)

did the same with my shielded Precision and no hum!!

need to get this baby shielded before I go for my second carped tunnel on Tuesday!

[gary mac]

Are you all sorted on the buzzing issue.

Good luck with the surgery.

[chrisanthony1211]

10 hours ago, gary mac said:

Are you all sorted on the buzzing issue.

Good luck with the surgery.

Just finished shielding the bass this morning and buzz all gone whether I’m touching the strings or not, that’s a lesson for me, shielding not grounding!!

[gary mac]

Great job, well done.

Diagnosis can be difficult, especially if the buzz is actually a hum or vice versa

[ped]

Great... there's nothing more annoying, and once you hear it you can't ignore it. Top work!

[chrisanthony1211]

Very happy 😃