The main Shielding Your Guitar page deals with what we could call “from ground up” shielding with copper foil and more refined about using braided shielding for existing wires or installing a shielded cable even. If you have not looked there yet, it might be a good idea to check it out as well.
The reason I wanted to add this separately is because an increasing number of pickups, mostly humbuckers but also some single coil can be purchased with a shielded cable already installed. So the shield is not the braided kind, but the way it is done with a large number of thin strands instead appears to be working just fine. I have mentioned that I come from a high frequency EMI world where you cannot get away with using anything but braided shielding, but in this case it is not as critical because we are talking a very limited frequency range in the very low end of the spectrum.
There are, however, a few things we need to evaluate before we can say that the cable and the shielding will satisfy the requirement of what we could call a proper shielding. The full list of shielding rules are outlined elsewhere, here is a condensed version that only apply the pickups that are delivered with a shielded cable.
Number 1: In order to qualify as a true shielding cable, the shield must be separate from all wires attached to the coil(s) of the pickup. This means that the total number of conductors, including shield, must be greater or equal to 3. As mentioned in a few places elsewhere, if the cable has one single conductor surrounded by a shield, the shield as such is worthless because it must act as a conductor of signal. If we have a signal conductor that is at the same time absorbing noise (as should be the only task of a true shield), the signal is automatically polluted. The only thing that we are trying to avoid by shielding, to keep the noise out!
Number 2: If you are using potentiometers and selector switches, no signal wires are to be connected to pot cases or switch “ground”. As we shall see later, not even the shield in the cable needs to be attached to a pot case or otherwise. Sometimes you see at the end of the cable opposite the pickup that the shield is soldered to one of the signal wires, this must be cut if you want to truly shield the guitar.
Number 3: Shielded cable must be used all the way from pickups through pots and switches to the output jack. Exposed areas around pots, jack and switches must be shielded separately and this shield must be connected to the cable shield in a way that leaves the whole signal path totally enclosed by the shield and that there is no contact to signal wires at all.
These are relatively simple rules, if followed, they will provide a good solid shielding for your guitar. The methods outlined on the main shielding page should still be considered, because they still apply as basis for shielding.
A special example is when the frame of a pickup has a wire attached that runs along with the other wires, the signal wires. This wire can be considered a shielding wire, or at least the start of a shield. A start, since there is no actual shielding, but this wire is completely separate from the signal wires and attached to the frame of the PU. A full shield can be applied by adding a braid to the already existing wiring and the wire can be cut and attached to the braid the the PU end. I will show an example later using a Lace PU.
As far as the output jack is concerned, I prefer to use a stereo version of this, as mentioned elsewhere, this approach has many advantages including being able to run the shield separately all the way to the amp.
Example 1: I want to install a Lace “Deathbucker” into a new guitar I built and I want to use the method mentioned above without using shielding paint and little or no copper tape and still have perfect shielding!
A Lace pickup like the one mentioned has 4 wires. The green wire is connected to the metal frame of the PU which is, by the way, part of the PU circuit. And this wire is ONLY connected to the metal (bravo Lace!), not to anything else! There is also a white/black wire, this is one of the signal (“coil) wires, we will run that directly through to the ring of the (stereo) output jack. The orange wire will run to the tip of the output jack. The white wire is not used, because this is a humbucker! It is the connection to a “mid-point” in case you want to destroy the pickup with this idiotic coil split nonsense! This wire is cut at the pickup and isolated with heat shrink tubing. The green wire is split from the neatly twisted wires. A braided shield is cut to length and the orange and white/black wires are pulled through it. The green wire is cut short and stripped so we can attach the end to the shield at the pickup end. So the braided shield acts as a shield and the green wire is attached to it so this is now acting as the “green wire”. The braided shield is eventually connected to the sleeve of the output jack. By the way, the instruction sheet on the Lace website tells you to solder the green wire to the white/black wire! Do not effen do this, that would ruin the shielding! Let us see what it looks like in pictures.
Preparing a Lace “Deathbucker” for installing in a guitar.
As shown in Fig 1, the PU is already delivered with a set of wires that are twisted, this will prevent some noise intrusion but not everything which is why we add the braided shield.
We see in Fig 2 that the two signal wires, orange and white/black are being pulled through the braid using a brass tube. As mentioned above the white wire is not going to be used, but it is connected so it will be isolated and hidden away. The green wire that is connected to the PU body will be connected to the shield. Notice also the piece of blue heat shrink tubing.
The wires are firmly attached to the brass tube that I used for this. It does not have to be a brass tube, anything rigid and thin can be used.
In Fig 4, the wires have been pulled through and the braid pushed up to the origin of the wires and the green wire has been pulled through the heat shrink tubing, ready to be stripped and put back into the tubing, in contact with the braid. We now have our PU body connected to the braid via the green wire. Notice, ONLY the green wire is connected to the braid that will become our shield.
Last step is to connect the green wire to the shield, Fig 6.
Next, we will trim and isolate the white wire, to make sure it is not accidentally connected to anything.
And we are ready to finish, after shrinking the blue tube.
And the job is finished, the shield has been secured to the PU body with some tape for better mechanical stability. At the top, you see the two signal wires, the only ones we need to connect to our stereo output jack along with our shield. The signal wires will be connected to tip and ring and shield to the body of the jack. All are separated and a special two conductor + shielded instrument cable has been made which has a stereo plug at the guitar end and a mono plug at the amp end. The shield is not connected to amp chassis before the amp input plug as it really should be in order to provide maximum shielding. The amp chassis is connected to earth ground through the power cable and the wall outlet.
Example 2: Rail-type PU already outfitted with a multi conductor shielded cable. I this case the shield is not my preferred type, but we are talking LF so we are probably OK. This type of shield is what is known as wound foil with a bare drain wire and it works better than having nothing. At least, it is properly connected to the frame at the pickup end. A little piece of the foil can be seen in Fig 9, the blue speck next to the PU.
Furthermore, we see the heat shrink (choice between red and black), the PU and the stereo jack. The objective here is to demonstrate how the jack is wired and shielding is performed. The red was picked because it may come out better in the pictures.
It is shown in Fig 10. The black wire from the cable is soldered to the tip, the green wire is soldered to the ring and the drain wire (the shield) is connected to the sleeve. This is the way it should be performed, so please do not mind the picture where the drain and green wire should have been swapped. Sorry!
The mistake was corrected before continuing, but the picture was already taken. In Fig 11, the red heat shrink tubing was placed over the jack connector to insulate and cover the terminals. The drain is visible by the blue heat shrink at the cable end. This also covers the additional leads, the connections to the PU center point. These are, of course, unused.
In order to keep the tubing in place it has been shrunk, we see the drain wire loop sticking out. Next step is the finish the shielding of the jack by connecting the applied copper tape to the drain wire. It can be done in different ways, here it is by contact which is sufficient. Make sure, however, that there is good contact. See Fig 13.
I used copper tape with conductive adhesive here because it is the easiest, but any type of conductive shielding can be used. Just make sure that the tape fully enclose and that there is good contact to the cable shield. One way to make it “neat” would be to enclose the jack in a copper tubing with proper termination to the shield of the cable.
As mentioned earlier, this was for demonstration purposes because there is no way you can attach the PU to the output jack and complete everything like this. Before installment, I have the free cable end from the PU and a cable attached to the jack as shown above, but with another “free” end. These two ends will meet in the control cavity for attachment to the control circuitry, if any.
As an example, the schematic in Fig 14 shows what have been suggested above. This schematic is also shown as Fig 4 on the main shielding page.
Even though it says “braided shield” as has been shown in Example 1 above, it could very well be a shielded cable as in Example 2. In this case, two wires are coming from the PU and the “shield” of the PU is only the base plate, note that the cable shield is only attached there and it does not in any way come in contact with the signal wires (red and black), the way it must be in order for the shielding to work properly. Note that the signal wire are not connected to the shield ANYWHERE. Especially NOT to the pot cases there as mounted are indirectly connected to the shield. The signal wires are equally important, this whole thing with “hot and ground” is total BS and does not belong anywhere. In this case, we chose the black wire to be “common” which only means that it runs through from PU to output jack without interruption, where as the red wire is connected to the circuitry, if any, which in Fig 14 is represented by the pots and the capacitor, C. Note that the strings are connected to to the shield and ONLY to the shield! The wires then run through a shield to the output jack where the read is connected to the tip, the black is connected to the ring and the shield is connected to the sleeve (the references used are related to the stereo plug in the guitar end of the special cable described above. As you may have noticed, there is NO “hot” and “ground” mentioned anywhere and NOTHING is soldered to the pot cases. The reason for this is obvious, we do not want the shield noise to couple into the PU signal. The whole purpose of shielding is to keep signal and noise separate.
“Bad” Shielding
I have mentioned this from time to time, don’t know if I always called it bad shielding, but one thing to remember, if you have not read my background in electronics and in shielding of very noisy products especially, the bad part is that the cable consists of a single wire with a shield around it which is supposed to be the second wire. I have written about the “second wire” elsewhere and hammered home that this wire is just as important as the center wire when it comes to conducting the signal from the pickup. It takes two wires to complete a circuit and they are in no way different as pointed out above. Just to illustrate what I have been talking about, Fig 15 shows a pickup with the type of wire mentioned.
And if you have not read on the general shielding page why this type is not recommended it is because the shield must be separate from the signal carrying wires to keep electrical noise away from these wires and can therefore not be one of them. Just think about it, noise mixed with signal equals noisy signal which is what we are trying to avoid in the first place.
To finalize this chapter, Fig 16 shows a close-up of the cable end. If we use this type we are introducing exactly what we are trying to avoid: A noisy signal!
