The Squier Project – Part 4 – Finishing up…

Ok, so the end of the road in sight, let’s finish this puppy up. We now have a our internals all sheilded, we’ll start putting in the electronics and then reassemble everything.

Now if you’ll remember from our earlier posts that our most important aspect of this project is to make sure that we have a good ground. This will ensure that our work is actually a shield, and not just another antenna. To start off, we need to figure out how we’re going to bond the parts to a common ground point. Fender generally does this by soldering everything to the back of the volume potentiometer. The rumor goes that this in fact sets up what is known as a ground loop. I strongly disagree. If you don’t do a good job soldering and making sure that all grounds have the same potential, then yes, it can create what’s known as coupling. Ground loops are actually something different, but I won’t get into semantics here. Let’s just say that if the wire soldered to the back of the pot and the shielding that you just added both have zero resistance and zero impedance to ground, then there is no possibility of it adding any noise to your guitar. It just can’t. It’s a physical impossibility. If someone can explain to me the mechanism that causes this, I’d be thrilled to know, as apparently my 20+ years of experience has let me down here.

I believe the theory arises from the possibility that the shielding and the wires connected to the potentiometer are somehow of a different potential to ground. This in fact could happen if you don’t do a decent job of soldering the wires, leaving some resistance. This can cause the wires and the shield to have a different resistance to ground, causing the possibility of one or the other “coupling” with an AC noise signal, offering the opportunity to inject noise into the circuit. The term “coupling” simply means that one of the parts is either closer, or more tuned to the frequency of the noise, setting up a differential between itself and ground equal to the amount of AC current induced on the part. Given that this is exactly how the guitar itself produces sound, you’re basically applying this noise at the output of the guitar, hence that inevitable hum. However, if the part is truly grounded, there can be no potential difference between the two parts. Ground is ground, you cannot make a grounded device go positive or negative in any way, else it wouldn’t be ground, would it?

The idea of a “ground loop” is different. There is some concern here, as many a guitarist over the years plugged in his guit and was killed the minute he started playing. This is actually caused by either a fault of the amplifier or a fault of the house wiring. The guitar itself has nothing to do with it, however there are a few things that can be done in an effort to minimize the likelihood of it killing you. If however, you don’t gig, and trust your gear not to kill you, you shouldn’t need these modifications to the guit, and they can definitely affect the tone, so you should consider all likelihoods, and choose the best option for your situation. I’ve chosen not to bother with any modifications to the original Fender design, and also have chosen not to worry about some phantom theory that I can’t logically explain.

So, the first thing I did was to add a good ground lug to the inside of the guitar. This consisted of a standard, tinned StakOn lug that I happened to have somewhere in the barn. I’ve got lots of loose bits and pieces in the barn. You know, “I’ll need that someday”, and into a drawer it goes. 99.9995% of those objects will still be in that drawer when you die. However, occasionally you can find a use for one of them. But just think of how after you’re gone,  your heirs will relish in how they now have partially used starter motor brushes from a 1964 Rambler American!

So I now take a wood screw, electrical lock washer (*internal teeth to bite into the metal that they will be in contact with), and find a good location in the controls cavity. I chose the vertical side where the hole is drilled for the spring retainer ground wire. This is probably the best place, as it’s away from the electronics and the screw won’t go right through the finish on the outside (which it would have, had I chosen the bottom of the cavity. So, I put the lug on the screw, and then the lock washer, and then screw everything to the side of the cavity, right through the copper shielding. The lockwasher makes sure that I have good electrical contact with both the lug and the copper shielding, as when it’s tightly sandwiched, the teeth bite into both the copper and the lug. Once it’s in, I verify I have a good ground by checking with an ohmmeter between the lug tab and the copper foil. Zero Ohms is the goal, and I have zero!

Once it’s in, I cut two lengths of black hookup wire about 7-10 inches long, strip one end of each wire and tin it (melt solder onto it). That complete, I then go ahead and solder both to the solder lug. One of these gets passed through to the spring retainer, while the other will go to the back of our volume pot. Here’s what it looks like:

Ground lug with grounds attached

Ok, so that’s done. We now trim up the other end of the spring retainer wire to length and solder that to the retainer. What I did was to pull it all the way through so that there wasn’t any slack, mount the spring retainer using the two screws, and then trim and strip the wire with some extra so that I could handle it. I then soldered it to the retainer, and just pushed the 2 inches (or so) of excess back into the controls cavity.

Ok, let’s deal with the pickguard and associated electronics now. First, we need to remove one of the wires from each pickup so that we can wind them around each other in a spiral or twist. This helps reduce the “coupling” I mentioned earlier. What happens is that if one of the two wires is closer to the source of noise than the other, one will have “more” noise on it. In actuality, it simply has better reception, so to speak. Because the two wires are carrying different levels of AC current on them, this will produce the familiar hum. By winding the wires around each other, you stop this potential difference in two ways: first, you make the likelihood of one being closer unlikely, and second by doing this you’re basically creating a very weak transformer. A transformer works by creating a magnetic field (like an electromagnet) in one coil of wire, which then induces current in the paired coil of wire. So, when you do this same thing to the pickup wires, you’re basically pitting one of the coiled wires against the other, so it’s like 2 transformers fighting each other (hey, isn’t that a movie?). The magnetic field of one wire pushes against the magnetic field of the other, effectively canceling out the noise. This doesn’t happen with the pickup, as the change in current is only applied to the signal wire, and not the ground, so there is no opposing magnetic force.

Wrapping the wires is simple if you putting in new pickups, as you can just put them in that way. Otherwise, you’ll need to unsolder one of the two wires, snake it around the other as far as you can from pickup to controls, and then solder it back to where you took it off. I recommend doing one at a time so that you don’t confuse which wire goes where. You shouldn’t need to do a lot of turns. It should be at most 1 turn every 1 1/2 inches or so. Less is fine, but make sure that you have enough so that the two wires of each pickup stay together.

Ok, so now we just need to connect the two wires from the input connector, and the wire from our ground lug and we’re done with the electronics. Connect the black wire or ground wire to the input connector that connects with the sleeve of the connector. You can test which is which using an ohmmeter, but in most cases you can see that one of the tabs/lugs connects to the tip, while the other one doesn’t. The ground tab/lug is the one that doesn’t connect to the tip connector. Solder the other wire, or signal wire to the tab/lug that connects to the tip connector. Once again, you want to wrap the wires around each other, just like we did with the pickups. Now, thread the two wires through the hole to the controls cavity. Then just solder them to the appropriate places on your controls. In a standard strat, the black wire will go to the back of the volume pot, and the signal wire will go to the lug on the volume pot. While you’re soldering the ground wire from the input, you can also solder on the ground wire from the lug that we added to the controls cavity. That way, we’ll know that the two are bonded electrically. That’s it! We’re done with the wiring!

Here’s what the finished wiring looks like:

Wiring the electronics

By the way, you can click on any of the images to get the larger version.

Ok, so the last thing to do with our project is to insulate the interior to keep our electronics from shorting against sides. The most important places to do this are the bottom of the controls cavity and the side of the control cavity where 3-way or 5-way switch is closest. You can pretty much use any electrically insulating material to do this, just make sure it’s reasonably durable, and will stay in place. In my case, I really liked the look of the copper, and didn’t want to hide it, so I chose clear plastic. Again, I happened to have a fancy, spiral bound brochure from a tradeshow with a clear, flexible, plastic cover on it. I merely cut it to the size and shape of the controls cavity, and dropped it into the bottom. It’s actually in this picture, but I couldn’t get my camera to show it:

Controls cavity with clear insulation

Controls cavity with clear insulation

Ok, so that done, we can now put the pickguard back on. When placing the pickguard, you’ll need to be careful to route your pickup wiring from each pickup through the routes provided to the controls cavity. It may work just fine if you happen to pinch a wire between the guard and body, but over time, with all of the extreme rocking-out you’ll be doing, you’ll be liable to damage the wiring. Just take your time, and using a pencil or chopstick or something, make sure that all of the wiring falls into the slots as you apply your pickguard. Once everything’s neat and in place, align the screw holes and attach it.

That’s pretty much it. Put your bridge in and connect the springs and apply the spring cavity cover (and attach the neck if it’s detached) and it’s ready for a setup!

In the end, I chose to not shield the pickguard any more than it already was. There were basically four reasons for this:

  1. There’s some debate as to whether this affects tone
  2. The controls cavity portion is already shielded, and the only remaining part that would be affected is the pickup wires which we twisted, so the effect would be minimal
  3. I’m lazy.

So the idea is that if after complete I’m still unsatisfied I can always do it at a later date. Additionally, I’ll probably swap the pickguard out at some point for either a pearloid or tortoise shell one, so I can easily shield it at that time anyhow.

So it’s complete! It still needs some tweaking in the setup, but for the most part it’s a keeper! I was testing it out in my music room, and turned on the florescent lights and I turned on a dimmer control lamp, and I could only hear a very slight hum in the bridge position. And as a comparison, I then unplugged that, and plugged in my single-humbucker Bullet Squier, and got an IMMENSE amount of hum! Which, as soon as I put my hand on the bridge, went away, validating my plan for grounding the bridge itself. Here’s the finished product:

The Completed Strat!

So I’m very happy with the result. It definitely sounds as nice as my MIM, although perhaps just slightly sharper, which is fine by me. It stays in tune, is very quiet, and sounds amazing. If you’re going to do a project to a Squier, then this is the one to do. All told, the final actual cost of the guitar was around $140, but again, I traded the two pedals, plus I have a second guit to show for it! So, in the end, the total out-of-pocket was $140 or so, but I traded 2 pedals in lieu of $70 that I wasn’t using, and ended up with a second bullet that’s probably worth $50, so in the end I’m really only out about $20! Even adding in the 2 pedals, that’s still only $90. So if it gets hurt, stolen, or I feel the need to pull a Townsend or Hendrix-after-Who, I’m more than comfortable with the loss, and can always do it all over again – but next time even better!

How is my Guit like a radio?

Radio waves work by radiating energy through space (it doesn’t need air, it just needs space). Radio stations work by radiating a specific frequency of radio waves. For instance, if your radio station operates at 590 on the AM band, it means that the station is radiating energy at a frequency of 590 kHz through space. In order to receive the signal from that particular radio station you need two things: an antenna, and a receiver that allow you to isolate that frequency from all of the other frequencies available.

How does an antenna work?

An antenna is made specifically for a particular frequency or frequency range. In the case of the AM radio, it is specifically designed to receive best somewhere right around the middle of the AM band. It’s total effective length is some fraction of the wavelength of the frequency. For instance, the wavelength of the 590 AM station we discussed earlier is 508 meters long. So, at the speed of light, in the time that the wave starts at zero, go to full positive amplitude, back through zero, to full negative amplitude, then back to zero, the total distance it would have travelled is 508 meters, or 1668 feet. This means that to receive that frequency, you need an antenna that is effectively that long, or some exact fraction of that. Fractional sized antennas are typically 1/4 wave, 1/2 wave, 5/8 wave or full wave of the wavelength, depending upon the frequency in question.

For our 590 AM station, a 1/4 wave antenna would have a length of wire of around 417 feet. Now, that’s obviously not the actual length of the antenna in your AM radio. Typically those can use an even smaller fraction (1/8 or 1/16 wave), and that’s only and effective length, meaning that other components (a loading coil or inductor) are actually making up the difference via electrical mechanisms such as ‘phase delay’. It’s not entirely relevant to this article, so I won’t get into detail, but suffice it to say that an antenna is a length of wire very suited to producing an electrical current when exposed to an alternating electromagnetic field (a radio wave). As an end-note to this paragraph, a typical single-coil guitar pickup has between 3000 and 5000 feet of wire on it, however it’s configured in a coil form with a ferrous core, which makes it an inductor, which means on the whole, it’s a very effective antenna.

What’s the receiver do?

Now that we understand that the antenna is the actual thing that detects a particular signal, what is it that the receiver does with this? The thing to understand is that although the antenna is “tuned” to the frequency to receive, an antenna by itself is very indescriminate. The antenna will receive a very wide range of frequencies, but it’s range is centered on what’s known as it ‘resonant frequency’. The resonant frequency is the one that it’s particular lenght is tuned for. So, how do I get just that 590 AM or 590 kHz frequency without anything else? You use a receiver, which filters out the adjacent frequencies using various mechanisms. The major component of this sort of filtering is what’s known as a bandpass filter. The bandpass filter can be a single filter mechanism, or it can be a combination of a high-pass filter and a low-pass filter, where the resulting overlap is the desired detection frequency. Basically, that’s all a reciever does – filters out everything above and everything below the desired frequency. Mind you, that’s a very simplifed description, but it covers just enough so that we can move forward.

And now the guitar part…

So, when you apply what you’ve just learned to your guitar, it’s now easier to see why you’re getting all that noise. In the way that your guitar has been built, it’s a very effective, albeit weak, wideband receiver. Given that the strongest radiated signal in your home comes from either your wiring or some other source of electrical device, that’s what you’re most likely to hear when you amplify it.

Some of the sources of that hum in your home or at a gig can be things like light switches, flourescent lighting, electrical motors (in refridgerators, air conditioners, sump pumps, etc), or possibly even from the transformer or wiring out on the street. All of these things will radiate energy and noise (known technically as EMI or RFI) in exactly the same way that a radio station transmits a signal, except the the energy radiated is not typically on a narrow band like the 590 kHz station. It’s more than likely across a relatively wide band comparitively, along with various “harmonic” frequencies. Harmonic frequencies are just like the ones in music, in that frequencies that are multiples of the original frequency can resonate along with the primary frequency. All of these things contribute to that “60-cycle hum” you hear so much about, and answers the question “how my Guit is like a radio”!