Grounding problem????

[plastik-bass[?]]

I recently got a MIM Fender Jazz and i love this bass i only have 1 complaint..

There is this buzz that goes on when im not touching anything but as soon as i touch anything metal on the bass it either goes away or i can barley here it. is this a grounding problem??? if so how can i fix this?? videos or maybe pictures are appreciated..


if it isnt a grounding problem what is it..and how can i fix it...again videos and or pictures are appreciated

[pkr2]

Originally Posted by plastik-bass[?]

I recently got a MIM Fender Jazz and i love this bass i only have 1 complaint..

There is this buzz that goes on when im not touching anything but as soon as i touch anything metal on the bass it either goes away or i can barley here it. is this a grounding problem??? if so how can i fix this?? videos or maybe pictures are appreciated..


if it isnt a grounding problem what is it..and how can i fix it...again videos and or pictures are appreciated

Make sure that the bridge is grounded.

[plastik-bass[?]]

Originally Posted by pkr2

Make sure that the bridge is grounded.

????

I've been playing for a bit over a year but im not so good on the setup & repair terms...

what do you mean by grounded

[plastik-bass[?]]

bumpizzle

[pkr2]

There is a wire that comes through a small hole under the bridge that makes contact with the bottom of the bridge when the bridge is screwed down to the body of the bass. The opposite end of the wire is inside the control cavity with the pup wiring, etc. This wire is connected to a common ground point in the cavity.

You can check for this problem by temporarily connecting a piece of wire between the bridge or any of the strings and the nut that holds the output jack in.

If the noise stops, it indicates a faulty ground. In that case, the problem will either be that the ground wire has a faulty connection in the control cavity or under the bridge.

Sometimes the wire will dent the wood slightly when the bridge tightens down and a bad connection results. Simply scrape the wire to make sure its clean and reposition the wire in a new undented part of the wood.

A multi meter or even a simple battery powered test light can also be used to check for continuity.

[Liko]

Originally Posted by pkr2

Make sure that the bridge is grounded.

WRONG. This is an all-too-common misconception. When you have a bass that makes noise when you're not touching anything but the noise goes away when you touch the strings, the bridge ground is fine. If the bridge ground were the culprit, the noise would INCREASE when you touched the strings.

The noise goes away not because you are grounding the bass through you, but you are grounding YOURSELF through the bass. You're 80% water and a lot of electrolytes, and yet your skin is very high resistance. Those qualities put together make you a very good antenna, and as such you are the biggest source of EMI, being so close to the bass and re-radiating all the noise around you.

This is not a grounding problem, it is a shielding problem. You said this was an MIM bass; is it brand new? Have any modifications been made such as upgrading pickups? New Mexis actually have decent shielding; the interior of the pickup and control cavities is given a shot of shielding paint, which is electrically conductive, and the shield in the pickup cavities is connected to the ground side of the circuitry (a pot shell, or the ground side of the jack). This shielding is better than some basses I've seen costing far more. However, no shielding is perfect; if your pickups are set high, or if you face a source of EMI noise (TV, computer monitor, compact flourescents, power strips, your amp), the shield is not positioned between the noise and the pickup coil, and the noise will be picked up. Also, if you swapped out pickups and didn't know that the little ring terminal was important, you've defeated the shielding around the pickups and noise will be introduced.

You can try to reduce the noise by shielding the cavities with copper tape, which has better conductivity. This may reduce noise a little more, but as the bass already has some shielding the difference will probably be small. If you've accidentally disconnected the pickup shielding grounds while swapping out pickups, putting those back in will drastically reduce noise. Just take the old pickups, snip off the ring terminal from the short ground lead going to the pickup (keep the longer lead that goes to the control cavity) and screw-solder that back in place.

Other ways to reduce noise are environmental, and include turning off nearby compact flourescents (you might consider a floor lamp or other light source with incendescent bulbs for use when you're playing), turning off the TV and computer if they're in the same room, relocating your amp so it's more to the side or behind you, and using the absolute minimum number of power strips to power your equipment.

If all else fails, some pickup manufacturers produce shielded pickups, and some luthiers will be able to shield your existing pickups, usually by spraying the inside of the covers with shielding paint and attaching a ground lead. Shielding the pickup coils themselves generally mellows the tone of the instrument, but the plus side is that noise is virtually nonexistent.

[pkr2]

Originally Posted by Liko

WRONG. This is an all-too-common misconception. When you have a bass that makes noise when you're not touching anything but the noise goes away when you touch the strings, the bridge ground is fine. If the bridge ground were the culprit, the noise would INCREASE when you touched the strings.

The noise goes away not because you are grounding the bass through you, but you are grounding YOURSELF through the bass. You're 80% water and a lot of electrolytes, and yet your skin is very high resistance. Those qualities put together make you a very good antenna, and as such you are the biggest source of EMI, being so close to the bass and re-radiating all the noise around you.

This is not a grounding problem, it is a shielding problem. You said this was an MIM bass; is it brand new? Have any modifications been made such as upgrading pickups? New Mexis actually have decent shielding; the interior of the pickup and control cavities is given a shot of shielding paint, which is electrically conductive, and the shield in the pickup cavities is connected to the ground side of the circuitry (a pot shell, or the ground side of the jack). This shielding is better than some basses I've seen costing far more. However, no shielding is perfect; if your pickups are set high, or if you face a source of EMI noise (TV, computer monitor, compact flourescents, power strips, your amp), the shield is not positioned between the noise and the pickup coil, and the noise will be picked up. Also, if you swapped out pickups and didn't know that the little ring terminal was important, you've defeated the shielding around the pickups and noise will be introduced.

You can try to reduce the noise by shielding the cavities with copper tape, which has better conductivity. This may reduce noise a little more, but as the bass already has some shielding the difference will probably be small. If you've accidentally disconnected the pickup shielding grounds while swapping out pickups, putting those back in will drastically reduce noise. Just take the old pickups, snip off the ring terminal from the short ground lead going to the pickup (keep the longer lead that goes to the control cavity) and screw-solder that back in place.

Other ways to reduce noise are environmental, and include turning off nearby compact flourescents (you might consider a floor lamp or other light source with incendescent bulbs for use when you're playing), turning off the TV and computer if they're in the same room, relocating your amp so it's more to the side or behind you, and using the absolute minimum number of power strips to power your equipment.

If all else fails, some pickup manufacturers produce shielded pickups, and some luthiers will be able to shield your existing pickups, usually by spraying the inside of the covers with shielding paint and attaching a ground lead. Shielding the pickup coils themselves generally mellows the tone of the instrument, but the plus side is that noise is virtually nonexistent.

Liko, for you to speak that authoritatively, I'm sure that you wont mind my asking for some sort of credentials.

As to any meaningful discussion with you, you made your statement and slammed the door shut.

I would have loved to have had an open discussion with you, if for nothing more than to explain that RF is such a small factor that it can be ignored in an audio circuit.

Look up 'ground loops'. Especially as the phenomena applies to audio circuits. You'll find no mention of antennas pertaining to ground loops.

Antennas are frequency selective with a very high Q at its resonant frequency. That criteria doesn't remotely exist in your theoretical explanation.

Think in terms of a Faraday cage with an open ground

Outside of that, hi, nice to meet you.

For the original poster: my suggestion still stands. If need be, I'll explain the temporary ground more fully. That's the simplest and quickest way to check it.

[plastik-bass[?]]

Originally Posted by Liko

WRONG.
This is not a grounding problem, it is a shielding problem. You said this was an MIM bass; is it brand new? Have any modifications been made such as upgrading pickups? New Mexis actually have decent shielding; the interior of the pickup and control cavities is given a shot of shielding paint, which is electrically conductive, and the shield in the pickup cavities is connected to the ground side of the circuitry (a pot shell, or the ground side of the jack). This shielding is better than some basses I've seen costing far more. However, no shielding is perfect; if your pickups are set high, or if you face a source of EMI noise (TV, computer monitor, compact flourescents, power strips, your amp), the shield is not positioned between the noise and the pickup coil, and the noise will be picked up. Also, if you swapped out pickups and didn't know that the little ring terminal was important, you've defeated the shielding around the pickups and noise will be introduced.

This is an 04 MIM Jazz and the bridge has been changed...but thats all(i didnt change it the guy i bought it from did)

[newfuture]

+1 to Liko

Your ground to the bridge is fine. If it weren't you would not have the reduction in hum when you touch the strings.

Am posting to add one other frequently overlooked source of NASTY RF: dimmer switches. If you're in an area with a dimmer switch (wall switch, halogen floor lamp, etc), these can produce horrible buzzes in magnetic pickups.

The suggestion about adding copper shielding the instrument may also help; it did for me on some very noisy instruments. There are good picture tutorials on this site about how to do it.

[plastik-bass[?]]

Originally Posted by newfuture

+1 to Liko

Your ground to the bridge is fine. If it weren't you would not have the reduction in hum when you touch the strings.

Am posting to add one other frequently overlooked source of NASTY RF: dimmer switches. If you're in an area with a dimmer switch (wall switch, halogen floor lamp, etc), these can produce horrible buzzes in magnetic pickups.

The suggestion about adding copper shielding the instrument may also help; it did for me on some very noisy instruments. There are good picture tutorials on this site about how to do it.

could you give me a link to one plz