So your bass has a hum

[Watchootognbout]

Can you see any kind of physical connection from the ground to the shielding? I am not familiar with your bass but I am guessing it has a ground wire coming from the bridge. Assuming it does, just run a wire from that connection under the bridge into the cavity shielding instead of taking the ground from your control cavity. If that make sense.

I will do that.On a different note,I was just comparing the electronics of both of my basses and I noticed something I didn't see before.The pickups in the fretless have THREE leads(First pic)


The pickups in the fretted have FOUR!!(second)


One of the wires in the fretted's wire group has thicker insulation and it's connected to a bus slot with another wire!(second)Hmmmmm!Any Ideas?I had just assumed that both basses electronics were exactly alike!

 

[DiabolusInMusic]

That I will do on a different note;I was just comparing the electronics of both of my basses and I noticed something I didn't see before.The pickups in the fretless have THREE leads(First pic)

View attachment 427354
The pickups in the fretted have FOUR!!(second)

View attachment 427353
One of the wires in the fretted's wire group has thicker insulation and it's connected to a bus slot with another wire!(second)Hmmmmm!Any Ideas?I had just assumed that both basses electronics were exactly alike!

Sorry, I am not familiar with your bass or your wiring. As I said in the initial post I am not an electronics expert, I just know shielding. Your issue does not appear to be RF interference but proper shielding can never hurt. I would make a new thread, you will probably have more luck getting somebody familiar with your bass and wiring. If they are the exact same electronics in both basses I would imagine that wire is doing something important.

 

[BlueTalon]

Do you have an ohm meter? Test for resistance between the bridge and the shielding. If there is no resistance the shielding is not connected to the bridge ground.

This is 100% incorrect. No resistance means the bridge IS connected to the shielding.

 

[DiabolusInMusic]

This is 100% incorrect. No resistance means the bridge IS connected to the shielding.

I stand corrected on this. Thanks for pointing that out. If you added copper foil under the bridge and soldered the ground to it you should see resistance.

 

[DiabolusInMusic]

Here is the picture of my Jaco jazz guts. This job was done previously so I do not have pictures of the process. The Jaco is based off a 62 so it has brass plates in the cavities. I am told this is some old school shielding but I honestly do not know. Since the plates are in there I decided to keep them in there. Most basses will not have these plates.

The elements of the job are the same. I added shielding material to the control and pickup cavities. My bass does not have surface routes but if yours does, ensure to shield them. Ensure to shield the pickguard over any surface routing. Obviously I am not about to put a guard on a Jaco.

There is a strip of copper foil underneath the bridge. The pickup covers are also shielded with copper foil. On this bass I used the copper foil over the screw holes technique, so there is no wire running to the pickup covers. You will notice the brass plates are grounded. This connection was there before, so I put it back; additionally, it also allows a connection to the cavity shielding.

The pickup plates are soldered to a metal plate stuck into the body wood, that is why you see two soldered connections on the plates. This is why you see no ground screw into the body with this job. Both of the pickup plate grounds come to a common ground in the control cavity.

There is no difference between when this bass is plugged in, with my hands off the strings, and when my amp is running with no input. Studio and stage worthy silence.

I hope that is sufficient to explain a Jazz Bass to folks. I intend to get a Stingray up later today.



P.S. Look closely at the body damage around the guards and sloppy paint edges. If I did not make it clear enough earlier, all tapes are not safe for all paints, particularly nitro. Please learn from my mistake, I know I did!

 

[BlueTalon]

If you added copper foil under the bridge and soldered the ground to it you should see resistance.

No. If you see resistance, it means something is wrong. You are treating resistance as a positive thing, and it's not. Less is better. A well grounded bridge should show NO resistance.

If you were to take the measurement from, say, the bridge area to a pickup cavity on an unshielded bass, you should read something like a 9 digit number of ohms. If you take that same measurement on a shielded bass, you should read something like 0 or 1 ohm. Wood is not a good conductor, which is why you want to line it with something that is a good conductor.

If you put the leads of an ohmmeter together, it will read 0 ohms. Why? Because there is nothing between the leads to cause resistance. If you touch the leads to a piece of metal, it will read 0 or something close to 0 ohms. Why? Because metal is an excellent conductor, and it's virtually the same as placing the leads together.

If you touch the leads to any two places on the grounding/shielding, you should read 0 or something close to 0 ohms. That means it is conducting very efficiently, which is what you want. The goal of shielding is to intercept any electrical energy that is not the pickup signal, and escort it quietly to ground. It can only do that if there is no resistance.

 

[DiabolusInMusic]

No. If you see resistance, it means something is wrong. You are treating resistance as a positive thing, and it's not. Less is better. A well grounded bridge should show NO resistance.

If you were to take the measurement from, say, the bridge area to a pickup cavity on an unshielded bass, you should read a 5 or 6 digit number of ohms. If you take that same measurement on a shielded bass, you should read something like 0 or 1 ohm. Wood is not a good conductor, which is why you want to line it with something that is a good conductor.

If you put the leads of an ohmmeter together, it will read 0 ohms. Why? Because there is nothing between the leads to cause resistance. If you touch the leads to a piece of metal, it will read 0 or something close to 0 ohms. Why? Because metal is an excellent conductor, and it's virtually the same as placing the leads together.

If you touch the leads to any two places on the grounding/shielding, you should read 0 or something close to 0 ohms. That means it is conducting very efficiently, which is what you want. The goal of shielding is to intercept any electrical energy that is not the pickup signal, and escort it quietly to ground. It can only do that if there is no resistance.

Is that not what I said? If he measures for resistance from the shielding to the copper foil under the bridge he will see a resistance. It will never read zero ohms, at least not any time I checked. Assuming he added the copper foil. This is how I check my shielding is connected.

I should add I have not busted out a meter when doing a shielding job for years. The job either works or it doesn't and I have enough experience (plus it isn't that hard) that I can visually detect where any shielding or connections need improvement.

 

[DiabolusInMusic]

Here we go with some Stingray pictures. I have not had this bass apart for years and don't like opening functioning basses, so this has some old school shielding.

I did this job with aluminum foil within the control/pre-amp cavity. I added rubber tape to the bottom of the cavity to prevent the pre-amp from touching any shielding. I did the pickup cavity in copper foil so I could solder a ground wire to it. That is the white wire you see in the pictures. I included two pictures so you can see it from different angles. I do not believe I added foil under the bridge but it might be there; I did this job years ago.

This job functions so I probably will not be updating it. Although, I really do like the naked, so I might redo the job just so I can have it look good naked. Tape will eventually lose it's adhesion but the this and the original P bass shielding job are testaments to how long tape can last. The P bass job is five-ish years old and the EBMM about two.

Here is the post I mentioned earlier in the thread where I describe my whole process in greater detail.

I don't really have any other style of basses with added shielding, so don't get too excited for more pictures. The fundamentals are all the same from bass to bass even though the layout of the job might be different.

 

[MovingPitchers]

My geddy Lee has those metal things underneath the pickups. And I went to my music dealer to check out some CS60S and on the box came those metal things for the jazz pickups...I wonder what those are

 

[MovingPitchers]

And I love these diagrams and explanations, DiabolusInMusic! Great work and amazing job on the three most popular designs!

 

[Moley13]

My geddy Lee has those metal things underneath the pickups. And I went to my music dealer to check out some CS60S and on the box came those metal things for the jazz pickups...I wonder what those are

I bought some after-market for my jazz. They're just thick shields. They used to be standard, but were phased out, considered unnecessary/excessive/optional.

 

[DiabolusInMusic]

I bought some after-market for my jazz. They're just thick shields. They used to be standard, but were phased out, considered unnecessary/excessive/optional.

Thanks for confirming this. I would be curious to know if those ever worked. Every bass I have had that came with brass plates still required shielding.

 

[BlueTalon]

Is that not what I said? If he measures for resistance from the shielding to the copper foil under the bridge he will see a resistance. It will never read zero ohms, at least not any time I checked. Assuming he added the copper foil. This is how I check my shielding is connected.

I should add I have not busted out a meter when doing a shielding job for years. The job either works or it doesn't and I have enough experience (plus it isn't that hard) that I can visually detect where any shielding or connections need improvement.

No, it's not what you said.

The whole point of using a meter is to check for problems in continuity that you can't see. And unless you have electronic microscopes for eyes, you can't visually detect anything as good as you can with a meter.

And how on earth do you know it's not going to read zero ohms if you don't check it?!?

Perhaps with conductive paint, you might read some resistance. Resistance is not good. With copper, you read zero ohms. Zero ohms is what you want. The more ohms, the less effective your shielding is.

 

[DiabolusInMusic]

No, it's not what you said.

The whole point of using a meter is to check for problems in continuity that you can't see. And unless you have electronic microscopes for eyes, you can't visually detect anything as good as you can with a meter.

And how on earth do you know it's not going to read zero ohms if you don't check it?!?

Perhaps with conductive paint, you might read some resistance. Resistance is not good. With copper, you read zero ohms. Zero ohms is what you want. The more ohms, the less effective your shielding is.

As I said initially, I am not an electronics expert. I know we are adding a conductive material that indicates a resistance when you put a meter to it, hence adding resistance. Put a meter on copper, aluminum or paint and you will always see a resistance. Copper has the highest resistance. I have never read a resistance of zero on any of my jobs, using any material including copper. It is usually in the .1-2 range. I checked for resistance the first time I did every different method of shielding to ensure it was all connected. Once I knew it worked there was no need to keep using it. The important part is that the bass is silent without aid from your hands, not that your shielding reads zero ohms.

The first time I had the meter out in years was to check the resistance from the shielding to the bridge yesterday. I had never bothered to check that connection because as you can see in the guide, the connection has been made securely with tape and solder. Additionally, I can just tug on the wire to see if it comes out from under the bridge. This job does not require a meter, it just can make it easier. Most TBers using this guide will probably not have a meter on hand, or ever in their life. If you have any continuity problems your bass will still have a hum that goes away when you touch the strings. It isn't difficult to open it up again and take a look. I have never had an issue that couldn't be visually seen when completing a shielding job. It's not like seeing tape over lap or broken solder connection requires a microscope.

 

[BlueTalon]

I know we are adding a conductive material that indicates a resistance when you put a meter to it, hence adding resistance.

You have that backwards. Wood is not a good conductor, so it has a lot of resistance. You add a conductive material to reduce resistance.

Put a meter on copper, aluminum or paint and you will always see a resistance.

That is simply not true. Putting the leads of an ohm meter to bare copper shows the same amount of resistance that touching the leads together has -- NONE. I know this, because I check it.

 

[BlueTalon]

Copper has the highest resistance.

I give up.

 

[Moley13]

Hahahahahaha. I've quite enjoyed watching you two battle it out over various threads

@DiabolusInMusic - I really feel that your heart is in the right place, and I think you've been genuinely very helpful by posting this shielding thread. Practically, pragmatically, your approach to shielding may well be absolutely fine in the vast majority of cases.

The problem is, you have a fundamentally incorrect notion of what "resistance" is, and what the shielding is doing (and why it's important that it's very conductive, and therefore measures a low (ideally zero - note, this is the mathematical/scientific use of the word "ideal") resistance.

Like I said, this actually doesn't matter if everything works. The problem comes when it doesn't "just work", and you need to have a way to diagnose the issue. Measuring resistance, and making educated inferences from the results is the most effective way to do this.

Please, please don't take this next request as an insult - I think you can really help a lot of people here on TB (and probably in RL too), but take a moment to familiarise yourself with some electronics theory. This is a great start: http://en.wikipedia.org/wiki/Electrical_resistance_and_conductance

Some key excerpts:

The electrical resistance of an DiabolusInMusic is the opposition to the passage of an electric current through that conductor. The inverse quantity is electrical conductance, the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical notion of Invalid Link Removed. The Invalid Link Removed unit of electrical resistance is the ohm (Ω).

Substances electricity can flow through are called Invalid Link Removed. Conductors are made of high-Invalid Link Removed materials such as metals, in particular copper and aluminium.

Further down, you'll find the typical resistance of 1 meter of copper wire which is 1mm in diameter is 0.02 ohms. Copper tape is a little thinner than this, but we are also making shorter runs, and it is much "wider" that 1mm (it's the cross-sectional area [roughly] which is important).

So yes, copper will never truly have a 0 ohm resistance - only superconductors near absolute zero (273.15°C or −459.67°F) can approach this.

However, for our application (and as far as our meters can read), it should be "notionally" zero.

This is extremely important in order for the shield to work. If you don't believe me, think about the resistance of wood - millions (billions? I don't even know) of ohms. If resistance was good, why does the wood of the bass not act as a super-awesome shield?

I might also address one more slight misconception you seem to have:

I know we are adding a conductive material that indicates a resistance when you put a meter to it, hence adding resistance.

EVERY material in the entire world has a resistance. For most materials, this is quite high. For some special ones, it is very low (relatively). Copper is one of these special cases. Thus:

Copper has the highest resistance.

Is false.

Now, if you choose to really get a handle on this stuff, your knowledge of the world will have greatly increased, but more importantly, your knowledge of bass shielding will be (essentially) complete, and you'll be a valuable resource to the TB community and the world.

I'd like that. You seem like a kind dude.

Hopefully this post has been helpful and clarifying. We cool, right?

--Moley

 

[BlueTalon]

However, for our application (and as far as our meters can read), it should be "notionally" zero.

That's why I used terms like "functionally" and "effectively" -- we won't ever hit absolute zero in our shielding with the budget most bass players have (Paul Allen could afford it, but not many others). Fortunately for us, copper is affordable, and gets really close to zero.

And you are right about our meters -- $10-20 at Sears or Radio Shack can get a very helpful tool, but it won't be as accurate as what is found in a lab. Measuring the resistance in bass shielding is an odd case where 1=0.


And to the OP, I'm not trying to be hostile, really. I'd love to compare notes with you sometime over beers.

 

[Moley13]

That's why I used terms like "functionally" and "effectively" -- we won't ever hit absolute zero in our shielding with the budget most bass players have (Paul Allen could afford it, but not many others). Fortunately for us, copper is affordable, and gets really close to zero.

And you are right about our meters -- $10-20 at Sears or Radio Shack can get a very helpful tool, but it won't be as accurate as what is found in a lab. Measuring the resistance in bass shielding is an odd case where 1=0.


And to the OP, I'm not trying to be hostile, really. I'd love to compare notes with you sometime over beers.

Yep!

">>>" (much, much greater than) is used all the time in maths/physics. Resistance of wood >>> copper, therefore when comparing the two for conductive purposes, it is acceptable to say copper = 0 ohms. An alternative perspective: if I ask "how many kilo-ohms of resistance does wood exhibit?", one could answer with a non-zero number. If I asked the same about copper... you'd have to say zero. This would even apply if I said "how many tens of ohms (decaohms).... " in most cases.

Barring super-cooled super-conductive materials in our basses, we ain't gonna get zero ohms. It would be "cool" though (aaawwwwwww, terrible pun).

 

[Pimmsley]

I give up.

Don't give up, you are right...

If the connections in the shielding are good/sound, meter should read effectively zero Ohms or very close to.

If the connections are poor you will get a resistance reading.