understanding guitar electronics
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entendendo eletronica em guitarrasTRANSCRIPT
Understanding Guitar Electronics
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This article explains how to visualize the path of the audio signal from your guitars pickups to your guitars amplifier.
How Guitar Electronics Work
Both the black and orange wire in the diagram to the left are representations of the wires inside your guitar and guitar cable. In every guitar cable there is a hot and ground wire. Simply put, if the signal from the pickups goes to the amp through the hot wire it will make sound. If the signal is sent to the ground wire before the amp then it will not make any sound at all. The whole idea of guitar wiring is to control how the guitar pickups signal gets to the amp. The guitar pickups signal is a lot like water in the way that it will always travel the path of the least resistance so if a connection is ever made between hot and ground wires, the signal wants to go to ground and no signal is heard.
Here is an example of the signal from the pickups being directed to the ground wire. The nail is metal so it will allow the signal to pass to the ground (the nail represents a wire). In this example there would be no sound coming from the amplifier because the signal from the guitar pickups is all going to ground. If you were to replace the nail with a simple on/off switch then you would have a primative volume control that can either be on or off.
It is far more practical to have a volume control rather than just a volume on/off switch. So, rather than just having an on/off switch we can replace it with something that will allow you to control how much of the pickups signal goes to the hot wire or the ground wire, a volume control. The way a volume control (potentiometer) works is by routing the signal to the ground
wire or to the hot wire. It does this by resistance. Imagine a water slide above a pool with water rushing down it. The water is the signal from your guitar pickups. The water only goes down the slide (the hot wire) because it does not have a more direct path to the ground (ground wire). If you were to cut a hole in the slide a lot of water would fall to the ground through that hole because that is the most direct path to the ground. If you were then to make the hole in the slide much bigger then a lot more of the water would fall straight to the ground. Now imagine that the size of the hole is controlled by a valve. This is essentially what a volume potentiometer is. It allows you to guide the electricity to the destination of your choosing. It does this the same way the valve did in the water slide example. If the valve is completely closed the water can not go anywhere but down the slide. If the potentiometer knob is at ten then there is too much resistance for the signal to go to ground and so it goes to the hot wire. See how to wire a guitar volume control.
So now lets take a look at how capacitors can be used to control the tone of a guitar. Here we have a capacitor bridging the gap between the hot and ground wires. Rather than redirect the whole pickup signal to ground, the capacitor will direct different frequencies to either hot or ground when wired like this. The capacitor allows the high frequencies to escape to ground so they are not heard. The frequencies that are redirected to ground are dependent on which value capacitor is used. Hear an example of how different valued capacitors sound in the same guitar.
Just like with the potentiometer as a volume control, the potentiometer can also be used to direct how much signal goes to ground through a capacitor. The idea is that you wire the capacitor to the potentiometer in such a way that the high frequencies in the signal travel the path of least resistance to ground when the tone control is at 10 but are not allowed to go to ground when the tone control is at 0. See how to wire a guitar tone control.
How To Solderstored in: Articles
Soldering is not difficult if you have the right tools. I remember when I first started to solder I was using a radio shack 15 watt soldering iron with super thick silver solder. I thought that soldering must be incredibly hard based on those first attempts. Soldering is actually quite easy and satisfying when you know what your doing.
Soldering Equipment
The Soldering Iron
Firstly, the soldering iron is going to be one of the more important tools you own for dealing with electronics. Soldering irons come in a few different types. The most common are the ones that plug right into the wall and usually have a switch to choose either 15 watts or 30 watts. These are fine for guitar electronics in my opinion, although, a lot of people say that if you want to get into electronics then you really should get a proper soldering iron which has a base that the iron plugs into and has variable heat settings. I have both types and I often end up using the cheap 30 watt soldering iron when I need to pack up and solder somewhere other than my work bench. The down side of cheap irons is that the heads often wear out or loose heat conductivity fairly quickly. They also can take ages to heat up and come with soldering tips which aren't very well suited for more detailed soldering work. The benefits of a proper soldering station (as they are often called) are variable temperature settings, very fast start up time, handle doesn't heat up and internal circuitry to compensate for when you are soldering to large metal surfaces like the back of a potentiometer, which acts like heat sink. The potentiometers case will conduct the heat away from the tip of the soldering iron very quickly. The result is that you end up holding the soldering iron to the pot for ages waiting for it to heat up enough to accept the solder (the cheap 30 watt irons really struggle when soldering to large pots). When you get a new soldering iron you should tin the head. This means that before you use it in your first project you should allow the iron to fully heat up and then apply the solder to the tip then brush off the excess solder. I'm not exactly sure why this is helps but i've noticed that it really does seem to help especially with the cheapy irons.
The Solder
After the soldering iron, the most important is the solder itself. These days I only use rosin-core solder. It has a lower tempurature melting point than most of the other kinds of solder and works the best when paired with the cheaper 30 watt soldering irons that are common at hardware stores. Its low melting point makes it easy to work with when dealing with capacitors that can easily be ruined by exposure to high temperatures. Rosin-core solder also behaves better than other solder. Because of the rosin in it, the solder will easily surround the solder joint.
The Third Arm Tool
When I began soldering I also didn't have this tool which is perhaps the most useful tool I have when it comes to guitar electronics. This is often called a third arm tool but it really works as a third and fourth arm. It's really the difference between pulling your hair out after 5 minutes of trying to solder the same two wires together and having the same two wires together in 10 seconds with a much better connection. With soldering you really need four hands. Two for holding the two wires together, one for the iron and one for the solder. I can not stress how helpful this tool can be. If you are just gettig into soldering, get this tool! You will not regret it.
The Solder-Sucker
Another tool specific to soldering that I use quite often is a solder-sucker. These are basically just little hand pumped vacuums that you use if you want to remove solder from a connection. If you are trying to salvage electronic components then this tool is really necessary. I also prefer the cheapest version of this tool which is just a little red balloon that you squeeze. You then put its nozzle to the re-heated solder and it will suck it up when you release the squeeze. The more expensive solder suckers are spring loaded and you have to set the spring everytime which requires both hands. The squeeze-suckers just require one hand to operate and are generally faster to use. With all solder suckers, you have to clean out the nozzle after a few uses because the solder will re-harden in the nozzle.
A Multimeter
This is a tool that is really handy when it comes to checking your work or trouble shooting. Although it is not really necessary in the construction and soldering phases of guitar electronics, when you finish a project and it does not work, you will want this tool to check the connections and see where the problem is. Its also helpful for checking if guitar pickups are showing the correct resistance for each coil. I have even used it to check the wiring of a series/parallel switch. I was sure it worked before plugging in and playing because the resistance values of the pickups combined showed what I expected. This is a great tool for checking the conductivity of a wire and for double checking certain pickup wirings.
Steel Wool
This is used to clean the parts that are about to be soldered. Steel wool is my favorite but sand paper works fine as well.
Wire Stripper/Cutter
These are necessary to cut and strip wires for soldering.
Soldering Basics
Preparing The Iron
The first thing to do is dampen the sponge that came with the iron under water, while the soldering iron heats up, and then squeeze most of the water back out. The damp sponge will be used to clean the tip of the iron after every use. This is important because the soldering irons tip will not heat up properly otherwise. As I mentioned above, if you have a new soldering iron, before using it to solder, let the iron fully heat up (about 5 minutes) and then lightly touch the solder to the tip of the iron (only on the part of the tip you plan on using). This prepares the soldering iron for use. After that pass the tip of the iron over the sponge to remove the solder. The soldering iron is now tinned and ready for use.
A Clean Connection
The most important thing when it comes to good soldering, besides the right equipment, is having clean wires and components. By clean, I mean having made sure there are not any finger oils or any impurities on the part of the wire or component that you are about to solder. I always clean the parts of the wire or components that I am about to solder with steel wool or sand paper. This ensures that I end up with a strong, conductive connection. If the parts to be soldered are clean the solder should effortlessly absorb in and around the parts. If the parts were not properly cleaned then there is a good chance that the solder joint will be cold (cold being the opposite of hot or conductive).
How To Solder
The first step after cleaning the leads to be soldered is to use the third arm tool to line up the two things to be soldered together. Assuming the two things are wire, they should be resting right next to each other in a way that the solder can easily join them. Next, get the solder ready in one hand and in the other hand heat up the wire by touching the tip if the iron to the part of the wires. It should not take long. About three seconds after applying the soldering iron, apply the solder right next to the tip and it should melt right between the wires. A sign of a good connection is when the solder melts from touching the wire rather than the soldering iron itself because it means the wires were hot enough to ensure a conductive connection.
An Example Of A Good Solder Joint
Testing The Connection
When just getting started with soldering it might be a good idea to test the conductivity of the newly soldered connection. After a few tries with soldering you will start to intuitively sense when the soldering joint has been done properly and you will not have the need to test it. When starting out though it is a good check step to make sure you are doing everything right. To check your work you will need a multimeter. You set the multimeter to measure resistance (does not matter which resistance setting as long as the
knob is turned to the "ohms" section of the multimeter. The meter will show "0L." if there is no electrical connection. If there is a an electrical (conductive) connection it should show numbers bouncing around until it settles on "0.00". This means that there is a connection (the zero means that there is not any resistance). So, to test the connection, simply touch one probe of the multimeter to the one side of the newly soldered connection and the other probe on the other side of the connection. If you see "0.00" on the mulitmeters screen then you know the connection is fine. If you see "0L." which should already be displayed, then the connection is not conductive and is no good.
Troubleshooting Guitar Wiring Errors
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Luckily, when it comes to troubleshooting guitar wiring, it can really only be caused by a handful of problems. Although I am still occasionally surprised by what causes these problems.
No Sound
- Hot Lead is Touching Ground Wire/Shielding
When you do not want there to be any sound you use a volume potentiometer to send the signal to ground. The signal, if given the option will always go to ground which causes no signal to make it to the amp through the hot lead. By the same logic, when you do not hear any sound from the guitar (when there should be) chances are you either wired some hot lead to ground accidently or somehow the hot lead is touching ground. The best thing to do is to go over your wiring and see were this might be happening. If you have no signal at all even in all the switch positions then the problem must be closer in the circuit to the output jack. Retrace your work from there.
- Female Jack Tip is Touching Shielding
It could be that the female jacks tip is touching the shielding or that a loose ground wire touching a hot wire. This can happen in Strats easily because the cavity for the jack is quite small. An easy solution is to cover the problem area of shielding with some sort of none conductive material like tape as well as reposition the jack so that it doesn't touch the shielding.
- Little Pieces of Metal Making Connections Were They Shouldn't
One time, a single piece of steal wool connecting a volume pots housing to one of its hot lugs caused the guitar not to sound. That one took forever to find! It is also the reason why I now prep connections for soldering with sand paper rather than steal wool.
No Sound In Certain Switch Positions
This is probably a wiring mistake. It is easy to make wiring mistakes at the switch because often a diagram shows one type of switch and you are using a different type. For example, Strat switches can function very differently. If you are sure the wiring is correct then refer to the "no sound" description above. It's probably a loose wire touching ground if it's not a wiring error.
No Sound and/or Crackling
- Loose Wire/Solder Joint
The most likely cause in this case would be a loose lead wire which is touching ground but loosely so that it vibrates with the guitar causing the crackling sound as it rapidly makes and looses the connection to ground.
- Bad Jack, Potentiometer or Switch
Usually you find this out after checking your wiring a 100 times. Occasionally you'll install a faulty Jack or Pot. It happens.
Normal Guitar Sound with Crackling
- Loose or Worn Out Potentiometer
I was once surprised to find that a loose potentiometer was causing a friends active bass guitar to crackle occasionally. Oddly the sound didn't increase when messing around with that pots knob. He even ended up ordering a replacement pre-amp before we discovered that the potentiometer was the cause.
- Loose Solder Connection
This can occasionally occur if a bad soldering connection is made. The vibration from the guitar causes the connection to vibrate which causes the crackling sound.
- Steel Wool Thread Bridging a Connection Between a String and a Pickup.
Although this might seem farfetched, it has happened to me a few times. The strand of steel wool gets magnetized by the pickup and bridges a connection between the string and the pickup.
Buzz
- Bad Jack/Jack Ground Connection
Without a proper connection to ground the guitar makes a horrible buzz sound. This is rare but sometimes caused by a faulty jack.
- Ungrounded Metal
This can also be caused by metal in or around the circuit which is not connected to ground as it should be. For example, ungrounded potentiometer housings. Another cause can be when a guitar is shielded improperly and a piece of shielding does not connect with the others it can cause this.
Horrible Buzz and Crackling
This can be caused by the same problems mentioned in "horrible buzz" the only difference being that the guitars vibration while playing causes the loose connection to vibrate and crackle.
About Guitar Pickupsstored in: Articles
Guitar pickups are pretty much the most important aspect of guitar electronics. Besides using capacitors to effect the tone of a guitar, guitar pickups have the most influence on the sound in guitar electronics. They can be wired to interact with each other to create a variety of different sounds. Guitar pickups work by transducing the vibration of the metal strings into electrical signals (an AC voltage usually between 100 millivolts and 1 volt rms). There are several different pickups but the most popular by far are passive humbuckers and single coils. Single coil pickups are made with a magnet at the base and a coil of wire which rests on top. The coil is one wire that has been wrapped around the six metal lugs or screws that extend to the magnet, thousands of times. the magnet in combination with the coil of wire, resting under a metal guitar string, will act as a transducer. The vibrating string of the guitar will upset the magnetic field generated by the magnet and induce an electrical signal in the coil of wire. The electrical signal can then be manipulated by volume and tone controls in order to shape the tone. The pickups can also be wired to each other to produce different tones. This happens do to the orientation of the magnets and the direction of the coil windings.
The Magnetic Orientation Of Single Coils and Humbuckers
Here is the difference of direction of different pickups polarities. As you can see, the single coil pickup has a different polarity direction than a humbucker. The single coils
polarity has its poles facing up towards the strings or away from them. The humbucker has its poles facing towards each of its coils. The reason for this is because the coils need to be one polarity, either North or South. The single coil pickup has either the North side of the magnet facing the coil or the South side of the magnet. The Humbuckers coils were cleverly designed to have one coil resting over the entire South end of the magnet and the other coil over the North end of the magnet. Humbuckers are design that way because having the coils with opposite polarity as well as one coil being wound in the opposite direction cancels out electromagnetic interference but doubles the amplitude of the guitar signal. The combination of the magnets being out of phase and the coils being out of phase actually causes the pickups signal to be in phase. This can be confusing but almost everyone, when talking about phase in the context of guitar electronics, is referring to the guitars signal rather than the magnets or coils. So when you hear someone talking about thin sounding pickups wired out of phase, they are reffering to the guitars signal from each coil being out of phase when they combine due to the coils actually being in phase (wound in the same direction) but with magnets still out of phase (opposite polarity).
Single coil pickups in the standard Stratocaster set up have the middle coil with opposing polarity as well as reversed windings. This is for the same reason as with the humbuckers. The reversed coil wiring and the opposite polarity cause the guitars signal from both pickups to be in phase with each other. Quite often you will see guitar pickups that are reverse wired and reverse polarity abbreviated to RPRW around the internet. That stands for: Reverse Wound Reverse Polarity, as you might have guessed. In some old Stratocasters, the middle pickup was not RWRP. This meant that the guitar signal was actually out of phase. The farther apart the pickups are, the more difference there is in the signal that they receive which means that pickups out of phase with each other that are far apart will be louder than if the pickups were next each other because less of the signal is cancelled out.