Guitar Electronics

Potentiometers “grounded”?

So, why do you solder everything to the case of the pots? Why? I see no reason to do that, at all! I have been searching for an answer to this question, why is the guitar circuitry like this, it has been like that for decades! One explanation could be that it was like this because it is from before electronics got really sophisticated as it is today. Could be because it is a compromise, it was to cover as many playing styles as possible. I believe it is time to upgrade!

You may have noticed: The pots in your guitar are NOT grounded – no they are not! The whole grounding issue becomes even more important when you are shielding your guitar! Please go check out the Guitar Shielding page.

“Shielded” Cable?

A normal guitar cable consist of one signal conductor surrounded by another, the “shield”. A shield is not supposed to conduct any signal, only the noise that it collects from its surroundings and therefor the shield needs to be totally independent of the primary circuitry. Again, please see the Shielding Page.

“Tone Capacitors”

Some capacitor types in my “tone” circuit sound better than others – no, simply false there is no difference between capacitors, pick the latest film capacitor, do not spend money on oil/paper, orange drop or other weird named capacitors, they do not make any difference other than maybe destroying the guitar pickup output even more than it already is by putting the circuitry there in the first place. Get a good quality standard film capacitor, they do not cost much.

Take this from someone that has been in the position of selecting capacitors for a long time, that would be for all voltages and applications, even the most demanding electrically and environmentally.

If someone in a video uses phrases like: “Bleeding off”, “grounding out”, “Ground”, “mid-scoop”, “nerdy”, “nerd-out” and many more, you basically know they have no idea what they are talking about, but they are trying to make us believe that they do know this stuff, they don’t! Do not fall for it! Unfortunately, as I can tell from reading comments to these videos almost all people believe this shit!

Guitar Electronics

This section is divided in two sections:

• Wiring, pots and other components and how to simplify. This has some parallels to other parts of the website
• Pickups seen from and electronic rather than a magnetic view. The influence of parts values and their effect is shown in a number of figures and diagrams. The extremely little importance of coil resistance is demonstrated. This value is unfortunately used to characterize pickups. Also, resistance is NOT the same as inductance of the coil. Very important!
• The real issues and advantages of active pickups is discussed
• The subject of wireless as opposed to cable is discussed
• Alternative wiring and output connectors are presented

Wiring and more

I have at this point watched an endless number of videos on YouTube about guitar electronics, the all solder wires and “shields” to the pot case. My question is why??? Not a single person mentions why they do that, it always seems like a serious act and I assume it has been done that way for reasons I don’t understand. You have read my background and credentials so you know that I am uniquely qualified to ask that question. As an EMI engineer I could imagine a reason why they would do so back around 1950, but my search for that reason has lead me nowhere! It appears to me that it would create more noise into the system than it would prevent it.

In case you have not looked at the shielding section, I strongly recommend that signal wires and shielding are kept completely separate, when you solder wires to pots that are connected to the shield through mounting it is for many reasons necessary to keep the wiring to a minimum. As explained elsewhere, there is no difference between the wires out of a pickup, they both carry the signal and we do not want any of them polluted anywhere in the signal path. Connecting pot cases with wires all over the place will only add to noise injection into the system. One general rule, none of the signal wires must be “grounded” in the guitar, only a shield should be grounded, the wire to the strings should be connected to this shield, NOT to the circuit and definitely not the pot cases! Warning: If you are using Gibson-style hardware for bridge and it is black (paint or anodized) instead of bare metal hardware, this type of finish may not be conductive at all, so the connection is not there at all! Please check your connectivity from strings to shield to make sure. Remember: The grounding takes place at the wall outlet’s 3rd prong. That is the closest we get to real ground!

As it is shown in the shielding section, the guitar wiring can be significantly simplified by following a few simple rules. And it never requires that anything is soldered to be back, the case, of the pots. As an example, here is a drawing of a pickup circuit, in this case a humbucker with a cover, here is what to do with the wire to the baseplate and shield, if any. The question is, why make it more difficult than necessary.

So why on earth are people going to great length and effort to solder a wire to the spring claw in the back cavity of a guitar with tremolo? It is very important to connect the strings to something that resembles “common”, but why do it this way? As an old EMI engineer, I know how important such a connection is, much more important than to solder, which is not the best connection. Here is my solution, drill a hole and use a screw, ring lug and maybe a star washer. You get a superb connection and you save yourself the aggravation of needing a 500 Watt soldering iron! Another relic from the past that makes no sense, I assume.

Just is case you were wondering how a single coil pickup wiring would look like, Fig 2 shows a similar way to wire in this case. Now, the output jack is a type that is usually used for balanced cables, a stereo jack if you wish. This issue is described in more detail on the Guitar Shielding page.

Now that we have the general things out of the way, let us start looking at the pickup from an electrical point of view. In the section concentrated on magnetics, we got to the point where we had created an electrical signal from mechanical vibration of the string and the induced voltage in the pickup coil.

Next step is to look at the pickup as an electronic component, the best way to do that is to look at the generally accepted equivalent circuit of a pickup. The easiest one is the diagram for a single coil pickup, and the simplest one as shown in Fig 1.

In Fig 3, Vs is the induced voltage in the coil, here represented by an ideal voltage source. L is the coil inductance and R_L is the coils resistance, in reality coil inductance and resistance are  only one component, but here split up in two for clarity. Sort of the same thing about the capacitance, C, that represents the capacitance of the pickup, not just the coil, but the capacitance as seen from the pickup leads. The capacitance will be discussed in more detail later.

Some diagrams also add a resistor representing losses in the pickup, typically due to eddy currents in metal parts that are somewhat ferromagnetic, in modern pickups that are only ferromagnetic where it is absolutely necessary, in places such as magnets and pole pieces made of steel, slugs and pole screws. Other parts like base plates and covers are made of a material that is transparent to magnetic fields, also the material is of very low resistivity so the eddy current issue is at minimum. Materials such as german silver and brass which are both high in copper content are excellent in this capacity.

In some forms of the simple pickup equivalent diagram the coil is split up in two halves as shown in Fig 4, this serves as a means to insert the above mentioned loss resistor.

If the two diagrams are plugged into a circuit analysis program the general outcome will be very similar because the influence of the resistor called R_loss does only have a very small influence on the pickup performance. In my research, I have not found any evidence that the equivalent diagram should be expanded any further than that.

To make the picture complete, Fig 5 shows how a humbucker can be represented by two single coil pickup connected in a specific way. From a circuit point of view, using laws of electronics you will notice the following if the schematics are compared: The output voltage will double, the pickup inductance will be twice the single coil inductance, same with the resistance, of course. The capacitance is a different story because when you connect two capacitors in series, their total capacitance will be half. Let us repeat here:

When combining two (single coil) pickups the total inductance will be twice and the capacitance will be half the value of the single coil. Please remember that.

Next we will look at the influence the variation in values will have on the frequency response of a pickup. Imagine that the voltage Vs created by the pickup based on string movement contains a range of frequencies, the question is, which ones will get through and to what extent. As we have seen, each of these have a certain amplitude and we will determine if they will get through undamped or not.

Before we get completely lost in the sea of frequency ranges and spectra, let us remind ourselves that the guitar has limitations when it comes to frequency “output”. The note E6 is 1319 Hz, that is the 24^th fret of the high E string, this probably has some 2^nd harmonic equals 2638 Hz. Most meaningful sound from the guitar is below this frequency, there is very little above that and practically nothing above 5 kHz. Good, because anything above 5 kHz is horrible to listen to. Believe me, I know! Thought you should know, so there is no need to fantasize about frequencies above 5 kHz.

The pickup the model used her is based on is a Seymour Duncan SSL-1, the values used in the equivalent diagram is from a study of 15 SSL-1 pickups conducted by T. Jungmann for a 1994 Master Thesis (See References). In our case here we are using the simple equivalent diagram with a resistor representing the pickup losses, all values are measured by Mr. Jungmann for the thesis. See Fig 6.

As mentioned, this is just an example, later we will look further into the guitar electronics and use a Fender pickup out of my own 1985 Stratocaster.

The SSL-1 is plugged into a circuit analysis program and to preclude some questions or even skeptics, this program is very capable and far from free of charge.

The circuit consists of a voltage source V1 representing the induced voltage created by the string movement. This represents an ideal voltage simulating the voltage created in the coil L1 with an internal resistance R1. The output capacitance was measured via a resonance test on the pickup and the C1 was calculated from this test using the other values measured. I must emphasize that the capacitance CANNOT be measured using a RCL meter of any kind, it must be obtained via a resonance measurement. R and L can be measured by a good quality RCL meter. Rloss is not measured, of course, it must be extracted through measurement and calculations all mentioned in the thesis.

The values of the pickup “components” and how to find them and their dependence on other factors will be discussed later, for now we will look into variation of components. For ease of understanding we will vary one value at the time, small variations for values that depend on other values, e.g. L and R, C on L . Other values can be varied more, but we will first look at the pickup itself.

One value connected to the pickup is the coil resistance R1, it is unfortunately quoted endlessly, probably because it is very easy to measure, but in fact the value is not a very good representative of the pickup in a selective situation.  If you turn your attention to Fig 7, it may be a bit confusing.

What happens, nothing! There is absolutely no way you can tell anything from the coil resistance, at least not when it is concerning frequency bandwidth. So a pickup with a high resistance is not “hot”? Not necessary! What we are looking at in Fig 7 is a resonance peak that does not change with coil resistance, what we see is 6 curves right on top of each other, in other words linking the coil resistance to pickup output is nonsense! I do wish that manufacturers  and pickup makers in general would stop using this value as an indicator, as we will see later inductance and resistance are not directly related.

Before going to the next parameter it is appropriate to mention exactly what we are looking at in Fig 7. The horizontal axis shows the frequency of the source signal, the voltage induced in the pickup coil. It is a so called logarithmic scale which means that the vertical lines go say from 100, 200, 300 and so on. It is done this way to make the low end of the frequency scale more detailed, basically for clarity.

The vertical axis marked “dB” and in this case it is linear because it can handle that and still maintain detail. The term or unit dB means that it is a measure of the ratio of input voltage versus output voltage:

As it shows, the curve sits on 0 for low frequencies up to a little above 1000 Hz (1 kHz) and after that it curves upwards to the peak where it turns around and drops very quickly. The significance of it being 0 means that Vout = Vin (in the circuit diagram Vin = V1). When the curve rises above 0, Vout > V1. If we look at the top end of a useful frequency range for a guitar, 5kHz, we see that the curve shows an output “gain” of 2 dB. The peak of the curve is resonance, the corresponding frequency is the resonance frequency, fo, and it means that impedance of resistor + inductance is equal to the impedance of the capacitor:

X represents the numerical value of the frequency dependent impedance of L and C respectively. The equation shows why the coil resistance has a very minor role in the description of the pickup and why it has no effect to speak of on the resonance frequency, simply because X_L >>> R. The subject will be described further later on in the text.

Next step is to look at the effect of small change in the inductance. Once the design of the pickup is final, that is the number of turns of wire on the bobbin, magnets or slugs  is final for a specific pickup, the inductance, L, is relatively constant. The curve probably shows an exaggeration of how much the value can vary once it has been set in stone.

Now, we cannot postpone it any longer, it is time to talk about pickup capacitance. Before we go any further I will warn you that if you believe scatter winding is the Holy Grail in pickup making, you will be greatly disappointed. Scatter winding is completely bogus as far as it meaning something to the performance of the pickup, at best it wastes wire because it requires longer wire than orderly machine winding! And if you look around, even former “scatter winding” believers have debunked that myth.

Capacitance of the pickup is a result of the fact that you can measure a resonance frequency. With the presence of an inductor in that kind of circuitry, it must be possible to assign a capacitance value to the pickup. So it is a function of internal as well as external parameters, of which winding resistance is the least important.

As shown in Fig 10, higher capacitance basically lowers the resonance frequency. In this case, for a specific pickup the capacitance range is huge, but it is done to show how it affects the frequency response of the pup. Now, again I cannot stress enough, pup capacitance is impossible to measure with a LCR meter, basically because there is no physical capacitor present.

Please see the subpage on Resonance Measurement for more detailed measurements of capacitance of pickups. As I hinted, it is a bi-product of the circuit, but as we also will look at, adding external capacitance will have same effect as adding internal capacitance (if we could).

Now we will change to a different pickup. As I have mentioned earlier, the pickup used in the previous examples was measured by someone else in a thesis from 1994. The data are good and it is documented well and, even better, you can go and check the information yourself. My treatment of the material is quite a bit more detailed with my own graphs and so on. The next pickup is one I have access to, because it is out of one of my own guitars, a 1985 Fender Stratocaster, and I have performed all the testing and measurements myself, and if necessary it is possible for me to go back and do more testing.

Here in Fig 11 we can clearly see how external components affect the characteristic of the pickup, especially the resonance peak, simply, if you use a low enough value you can actually flatten out the peak. That is making the pickup response more even and you can argue that it is inconsequential because the curve for 150k load (dark blue) starts to drop off above 7 kHz somewhat above any frequency the guitar puts out no matter how hard you wish.

Maybe it would be prudent to show a diagram of the 1985 PU before we continue with external circuitry:

Let us look at how it will shape the output frequency characteristic if we add a 250k resistor simulating the typical Fender volume pot and add a pot, also 250k in series with 22nF capacitor, the latter I call an “enot” circuit, I have explained elsewhere why I call it that (excuse my sarcasm). If we vary the enot resistor value and leave the volume pot fixed as a 250k load, this happens, Fig 13:

As it can be seen from the figure, if we go below about 150k in enot pot resistance, we start to cut into the what we could call the “useful” range of frequencies from the guitar, if we get as low as 25k, the curve start dropping at 400Hz, remember A5 is 440Hz, 5^th fret on the high E-string, so everything is dampened quite a bit. Remember if the output is down 6 dB it means “half” output.

Many, many combinations can be exploited including different capacitor values, but that could end up being extremely complicated and the purpose here is to show and explain the principles of the circuitry, why it is done this way, I can only speculate and I usually do not do that. Why a 250k pot is selected should be obvious, because it gives us a flat frequency response of the pickup. We maintain a very similar look when we “destroy” the pickup output by adding a pot with series capacitor in parallel with volume pot.

Here is what we in this context will consider a “complete” system (Fig 14). Now the load has added components in the form of cable capacitance and amplifier input impedance.

That maybe a large jump, but we can always go back and see what the cable capacitance does to the system.

Removing the cable capacitance stretches the frequency domain far beyond the capability of guitar and pickup. As we can see, the cable capacitance will eat up everything an idiot pickup maker will claim is so great and unique about his pickups, scatter wound and other BS.

Rounding off this discussion about single coil pickups we can see that these have plenty of capability when the question is about frequency range and as it may have surfaced, I am not a fan of so called “tone” circuitry, which is why I mention this part of the guitar electronics as “enot”. There is logic to the term I use, it is backwards and should not be there. As you may have noticed during the discussion of the graphs, especially the one covering the enot pot settings that there are settings that make no sence. If it was me, I would recommend a fixed circuitry that straightened out the frequency characteristic to dampen the resonance peak, I am sure that would stabilize the sound of the guitar. The volume pot, I am afraid, is much more difficult to get rid of, but as we will take a look at later there are ways to deal with the ill effects of this ancient and simplified circuitry that is still dominating the guitar world. I am a proponent of bringing out the raw natural pickup sound, if you can say that a pickup has a sound by itself, but raw and natural sound it means mimicking the string movement in a way that is possible for a magnetic pickup.

In order to demonstrate the difference between a single coil and a humbucker I picked one designated #1 in my test portfolio. I have forgot to mention something, in all the pickup schematics up to this point, the label for the voltage source has been “sine 1kHz”, this frequency is the fixed for the source and used for time domain analysis, but it is suspended, obviously, for the frequency sweep, so for these curves this label is meaningless. Here is the sweep curve for the pickup in Fig 17.

As can be seen from Fig 18, the resonance frequency for the pup has dropped to about 7 kHz, somewhat lower than for a single coil, but still within the range of natural guitar frequencies.

Magnets are covered elsewhere and how they influence the pup’s output, how the output level influences the final musical experience, meaning the sound coming out of the speakers, will be in a different section, since there is no contribution from the pickup itself. The wire insulation discussion is mostly a waste of time and energy because the influence on FSQ is so infinitesimal that it does not matter compared to many other things. As far as wire gauge is concerned, the only thing that matters is mentioned in the next example.

I grabbed a cheap pickup that came in a set of 3 since it was promoted as part of a Fender replacement set, so basically a single coil pup. I will elaborate quite a bit here because it is supposed to be an educational example. The pickup is part of my test batch and is called PU 7, just in case you run into it in a different section.

This is what you might refer to as a “cheap” Chinese pickup, single coil Fender style pup with cover and everything. It differs from a Fender significantly because instead of pole piece AlNiCo 5 magnets, it had regular steel slugs top to bottom and a ceramic magnet in the bottom.

Now, in my lab, I have the capability of measuring just about everything about a pickup before putting it in a guitar, once the pup is in a guitar, I can measure everything else using Pro Tools with plugins. For now, I will use my capability to measure resistance of coil, inductance, resonance frequency and calculate capacitance of pickup as seen from the terminal wires of the pup.

Since the testing here is with no movement, I am not using my specially designed string vibration testers that I built and used for the magnetic part. Here, in order to measure the above mentioned parameters, I need: LCR meter, oscilloscope, function generator with variable frequency and maybe a regular multi meter. You can use the LCR meter to measure L and R, inductance and resistance, never ever C, capacitance, you might get a value on the display, but it will be totally bogus and unusable, may even be negative in value! Anyway, the well established and only legitimate way of measuring capacitance is to measure the pup’s resonance frequency and then use L and R to calculate C. Since R is just a few kOhm, it does not influence the C calculation much so R can be omitted for a simpler calculation. To measure resonance frequency you can use one of two methods, the amplitude method or the phase mode, I use both, but the latter is probably the most accurate, but it also requires the most expensive equipment. Either way, both methods require the function generator. A detailed description can be found under this tab as a subpage.   

The experiment was conducted like this: The magnet and slugs were removed and data were measured, Case 1. The slugs were added and measurements were repeated, Case 2. Shorter slugs were added and it should be noted that “upside down” means that the slugs were flush with the top of the bobbin, Case 3 & 4. Finally a set of AlNiCo 5 Fender style magnets replaced the slugs.

It is worthwhile to pay attention to what the information in this table tells you, if you take a look at Case 1, this is the coil of the pickup only, no “core” as it is normally called, another description for it, an air core. It is just a specific coil with a certain number of turns of wire and the inductance of that tells us a lot, not to mention the resonance frequency, fo, and the resistance of the coil. Stuffing a lot of ferro-magnetic material in the coil will increase the inductance, in this case almost triple the inductance, yet, the resistance stays the same, of course. The capacitance drops about 25%. If you take a look at the resonance frequency, it is the highest with the inductor being just an air core, which is not very unusual. Adding a core increases inductance, pretty normal too and is a trick that is used by electronics engineers all the time.

Taking a look at Cases 3 and 4, we simply add cores of a different sizes, Case 3’s are unable to fill out the entire length of the pickup coil. I have not investigated this further, but I have a feeling the slugs in Case 2 and Case 4 are made out of almost the same material, the difference in inductance is relatively small.  The slugs in Case 2 and Case 4 are same size, Case 3 are smaller.

The most interesting case is comparing Case 2 to Case 5, looking at the inductance in the two cases, there is a huge difference. What is the conclusion we can draw here, it is that the parameter no one pays any attention to, the inductance, is about cut in half. This is very important especially if we take into account the capacitance added later on in form of cable and other capacitance, it will cut down on the useful bandwidth of the system, cutting the higher frequencies as we have seen above.

I have watched videos on YouTube with individuals that took cheap Chinese pickups (hint: Case 2) and removed the ceramic magnet in the bottom and the slugs and replaced them with AlNiCo 5 magnets and claimed they got an improvement in the sound. Now you know why, even though they do not know themselves!

Now you might say, there is a difference in capacitance, true, but if you think about that difference is minimal considering what is added later on. It might be small changes, but do not forget that nothing about the coil has changed, not wire resistance nor number of turns. Take that to heart scatter winder prophets!

Last interesting part is if we compare the capacitance in Case 1 and Case 2, that is an interesting thing to consider that the presence of steel slugs takes part in defining the capacitance of a pickup, much more than some insignificant difference in winding method!

What else can we make out of the numbers and other things we can measure?

Resistance and Inductance

Where µ_r is the permeability of the core material, µ_o is the permeability of air, N is the number of turns in the coil, A is the effective area of the coil (the opening, if you wish) and finally, l_coil is the length of the coil (the height of the pickup coil).

With the above definitions we can see that A = w_a ∙ b_a, the average area of the coil. So if we return to the table in Fig 17, we can try to use the various measurements to determine the number of turns in the coil, if we would wish to do so. Start with combining all the parameters that are constant into one parameter, K_pu, that, of course, is also constant, even though ρ is unknown it is still constant, then you get:

An important lesson we can learn from the above equations is that coil inductance is proportional to the number of turns in the coil squared (N²), secondarily dependent on the material used for slugs in the coil to “supply” flux to the pickup. The resistance in dependent on the number of turns (N) and nothing else if you use the same coil for the pickup. So it is indeed very, very wrong to state that the coil resistance is the same as inductance, and it is not exactly correct to state the output is synonymous with resistance R, even though output voltage is proportional to the number of turns, N. There is much more involved, please see the section on pickup magnetics.

Active Pickups

First of all, let us get straight, there is nothing active about the pickup itself, it is still just like the regular pickups with bobbin, wire, magnets or slugs and so on, we have just added a little circuit that adds a lot of nice qualities to the total, we will look at some here.

It has been said that going “active” adds certain things to the signal like compression and it is really loud, because the output voltage has been amplified before it leaves the guitar. Those along with other misconceptions have given active pickups a lot of “thumbs down”, a bad reputation, if you wish.

Now, I am here to tell you that it does not have to be that way, because a well designed active pickup is superior to any standard pickup, even the ones from the 50ies (ha-ha).

The active part of the pickup is centered around an opamp, typically a little single chip amplifier in an IC. There is a lot of different opamps out there, but if you should come to have to pick one, please pick one that is intended for audio, possibly with a JFET input and that it can be operated rail-to-rail, not that we would need that in a “normal” application. The whole circuit is operated from a power source, typically a 9V battery.

The great disadvantage of a regular pickup is that when ever we change the settings on our guitar controls it changes the characteristics of the pickup because we change the load impedance of the pickup, as explained above. Used correctly, the opamp will remove this drawback, because the opamp has an extremely high input impedance. That means that the pickup is completely unchanged regardless of what is hung on the output of the opamp. Remember that I said well designed not all active PU circuits are! Some circuits will actually still change the loading of the pickup, something we are trying to avoid.

The pickup itself represents a very high impedance so with the opamp input also being a high impedance we have what is referred to as a impedance match. So if we go back to the simple pickup we add some insanely high-ohm potentiometers to the output of the pickup, volume control etc. Still we have an arrangement with an extremely high impedance, now mainly resistive. A high resistance combined with a large capacitance, for example in your cable, will be a low pass filter that cuts off the or at least dampens the higher frequencies in you output, these, of course, will not reach the amplified. Problem!

Problem solved with the active pickup approach because the opamp has a low output impedance that will eliminate the cable capacitance problem, well, at least minimize the problem. Well, it will not eliminate the cable capacitance, but it will drive the capacitance with a much lower impedance, thereby eliminate the filtering effect. Also the pickup is not bothered by the control circuitry that is now located at the output of the opamp and the potentiometer value is very low.

Another reason why active pickups got a bad reputation because the the gain was set way too high causing all sorts of problems, but a well designed active circuit matching the pickup will give you a lot of pros and eliminate the cons. You can even set the gain close to 1, meaning that the output of the opamp equals the signal from the pickup with no problems. Big difference is that the pickup characteristics do not change when you manipulate the output controls, if any. Just do not put any “control” circuitry before the amplifier, that would ruin everything! Stay with just resistor as shown in Fig 21.

There are circuits available online from people that have investigated active pickups. Fig 21 shows a circuit that is in line with the known published ones, this on is with modifications implemented by myself. This circuit is, as I said, very simple and therefore cost effective. I have developed a more elaborate circuit that I may publish at some point when verified. On the left, in Fig 21, is the pickup in the dashed line box, to the very right is shown a resistor connected to Vout, this is to represent the amp input voltage that would be across the amplifier input impedance, here called Ramp. The opamp used in this circuit is along the earlier recommendations calling for a audio type opamp. That is different from what you see in standard active pickups. You may have noticed that the pickup used is more like a single coil, it could very well have been a humbucker. In this case the active part is tuned to yield a gain of about 1, in case a humbucker is used, the gain must be adjusted to a proper value consistent with the raw pickup output. Well, that is what I would recommend.

With the correctly designed circuit, you can get to a point where the pickup can be operated to its maximum potential all the time and any signal adjustments can by done without altering the pickup performance. Note one thing, in Fig 21 where it says “Vin” there is a resistor R20. This resistor is added to give the pickup a flat frequency response as input to the amp circuit without changing anything on the fly as a volume pot would. One caution here, beware a little but with some of the DIY circuits out there, sometimes the output gain is dependent on the choice of component values

Well, the only drawback is that the circuit requires a battery change now and then. Even that has been addressed by rechargeable battery packs that can be built into your guitar.

Wireless Systems

When it comes to wireless guitar “cables”, I have been using these for decades, mostly along with regular short low-capacitance cables. I must admit that with the wireless systems being of better and better quality and reasonably prices, these days, I use wireless almost entirely. They are small, plug directly into your guitar and have 4 channels available so the possibilities are endless. An example, say you have one transmitter plugged into your guitar running on one channel, you can actually have up to 4 receivers plugged into different amps or other devices, all switched to the same channel, in fact splitting your signal up without any ill effects, like “overloading” your pickup. You can also have the receivers on different channels and switching the transmitter to different channels at will. The system I am using is relatively economical and there are no unhandy transmitters or receivers to deal with with antennas sticking up everywhere.

Not only is the cable capacitance problem solved, there is no noise injection because the signal transmission takes place at a frequency way above any noise frequency and the chance of electrocution is about zero! The wireless , however, does not change the issue of the control circuit loads the pickup.

The system I am using is warning against active pickup systems, but if you run it at low output levels, it will not overload the transmitter. Tuned as suggested above will eliminate this problem. Only issue, really, that it is a but hard to change channel on the fly. If you would you could have receivers attached to different inputs so you could change between amps, for example.

There are many variants out there, but some time ago, I wanted to try the relative low cost systems, At the time, there were not many of the around, so to me X-vive looked like something to try so I go one set to start with and I did not have any issues to speak of before i tried it in a room that is bursting with Wi-Fi and Bluetooth from many devises where I got a frequent cut-out every 10 seconds or so and it was just a blip but enough to disturb the playing to a point that was annoying. Well, the problem is the technological evolution and the fact that they all use the same frequency band 2.4GHz. Yes, I did say band because the are a number of channels (I think it is about 60) that go by the “name” 2.4GHz. Also, most wireless guitar systems use these channels and some T/R systems have more than 1 channel, 4 is the typical number and I believe that these are fixed. Now, if the number of applications using the 2.4GHz band it becomes extremely crowded and interruptions can become a problem. I got a tip when watching a YouTube video that was about different systems and one of the systems recommended from this very comprehensive test was a T/R system named “Ammoon”, this had a distinction from the rest of the systems running in the now very crowded 2.4GHz band, it used the 5.8GHz band! Testing this system in my one room bursting with 2.4GHz, I had absolutely no problems with the Ammoon in that room. Now it should be mentioned that all these systems are low cost systems that most likely operate at fixed band frequency and therefore are much more prone to interrupts in the 2.4GHz band than in the 5.8GHz band. There are systems that are several time the cost of the above mentioned systems, they are, however, free of errors because there are separate communication between transmitter and receiver such that they can select channels that are free and be able to communicate this.

Final note:

I have not mentioned much about components, pots and capacitors, for guitar circuits here. Some of the crazy stuff and myths have been mentioned in the Q and A section.

Here is something I have been experimenting with on a guitar with two pickups. Instead of using a regular output jack, I have used an XLR and since it is out of the guitar it is the “male” kind with pins. Fig 22.

The pickups are shielded as indicated on the Guitar Shielding page, with truly shielded cable, attached with just shield connected to the baseplate. As it can be seen, the two pickups have a common connection, the black lead and two separate connections for signal. The shield is completely separate as it should be and will be eventually connected directly to Earth Ground. The “box” named RN is a resistor network, in its basic form just two resistors providing each pickup with a flat frequency response as indicated above.

How about taking this a bit further? In Fig 22 we brought out the two PU signals separately and the only problem here is that it is not possible to use a standard cable for this so if we want to use this method, a special cable needs to be made (at least to the best of my knowledge). If we turn our attention to Fig 23, we still have two pickups, but we introduced a switch, Sw, to select the pickup that we want to use.

The advantage here is that we can use a standard balanced XLR cable, exactly identical to the cable used with microphones. Only difference here is that we do not take advantage of the full potential of the 3-pin XLR connector and use the case as shield, but shield is connected to pin 1, pretty much “wasting” that pin. What we do get, is the balanced advantage along with a shielding of the signal, the first requires that the amp input is balanced, if that is not the case, the XLR cable needs to be properly shielded. Most guitar amps and amp heads do not have a balanced input so some of the advantage is lost here. I do not remember if I have explained it elsewhere, but a balanced signal transfer needs a differential input on the amp or other audio device to work fully. For other devices such as computer recording interfaces and multitrack recorders have balanced XLR inputs that give you the full benefit of implementing the suggested circuit in Fig 23.

One more thing to notice in Fig 23 is that we have combined the cable runs to the output jack, by using a three conductor shielded cable and combining the two runs at the last pickup. This is, of course, not absolutely necessary, but if you have to mess with the wiring, which is very likely if you want to achieve great shielding. As I have mentioned elsewhere, there are only very, very few pickups that come with proper wire as far as shielding is concerned, please see shielding page. The use of stereo plugs in connection with “mono” shielding is also mentioned on that page.

Well, I come up with stuff all the time so if it is worthy of adding here, I will do so. The additions will most typically appear as sub pages that can be seen if you “mouse-over” the main page in the menue.