We broke up like this:
[…] In the next episode we will examine in more depth the sound characteristics of the pick-ups based on their construction characteristics and their positioning. Obviously, as mentioned in the title, we will also examine the passive component, i.e. potentiometers and capacitors which, together with the pick-ups, contribute to the formation of the circuit and contribute significantly to the final sound.
As the most passionate and experts know, the topics just mentioned have been the subject of entire books and therefore wanting to summarize all the technical aspects in the short space of an article is hard to say the least. This is why I will mainly report the general concepts, as they emerged from scientific knowledge as well as from international literature, obviously combined with common experience (which perhaps interests the “curious and experimenter” musician more).
In the first part of the article we saw what a pickup, now we will examine other aspects which, involving the pick-up, contribute to the final sound.
Pick-up positioning
The first observation that you can easily make is: taking the same pick-up and placing it in different points of the guitar (more or less close to the bridge or neck) you will get different sounds and a different emission volume (with the same height of course).
The reason? Following the vibration of the string, a fundamental note and some of its harmonics will be produced.
In the study of oscillatory phenomena, the harmonic frequencies are the frequencies whose value is an integer multiple of the base frequency (fundamental frequency).
For example: a wave of 100 Hz it will be composed of a fundamental frequency of 100 Hz and of different harmonic frequencies, of 200, 300, 400, 500 Hz, and so on, with variable amplitudes.
Another concept to keep in mind is that the points where the strings do not move are named Nodi and the points where the string vibrates at its maximum amplitude are defined antinodes.
Obviously, as you can easily guess, if we place the pick-up at the maximum point of oscillation of the string (antinode), it will collect the sound to the maximum, because the perturbation of the magnetic field will be maximum. By placing the pick-up in the nodal point, the magnetic field will not be disturbed and therefore the pick-up will not pick up any sound.
If a rope in length L emits a note, for example an A (first harmonic), the same string will vibrate with less intensity even at double frequency (second harmonic), triple, quadruple, and so on.
We can thus schematize:
For the fundamental, the amplitude is maximum in the center and becomes zero at the ends.
For the second harmonic it is zero at the ends and in the center and is maximum at a quarter and three quarters.
For the third harmonic, the amplitude is zero at the ends, at one third, and at two thirds and is maximum at one sixth, at half, and at five sixths.
And so on.
It is therefore easy to understand that, depending on where we will place the pick-up, we will have the possibility to collect a certain number of harmonics with different amplitudes and this will affect the composition of the sound and its volume.
In Fig.1 it is possible to see how each pick-up, in relation to its position, will understand differently.
Passive circuit
Once the magnetic field has been perturbed by the vibration of the string, an electric current of the order of millivolt.
It is now known that the millivolts generated will depend on the construction of the pick-up (coil single /humbucker, number of coil windings, composition of the magnet ...) and generally they will be around a hundred millivolts.
At this point, the signal thus generated will meet the volume control and the tone control along its path.
The quality of these components is fundamental; it must in fact be borne in mind that, even when the controls are fully open, the signal will still pass through them (they are never completely excluded) and therefore will affect the final result.
Some guitarists, as an extreme situation, prefer to eliminate the volume and tone controls and use the direct output of the pick-up to send the sound as faithful as possible to the effects and amplifier.
While respecting the choice of purists, I personally think that this solution limits the versatility of the instrument.
Using volume, tone and their adjustments can greatly contribute to the guitar sound. If we made a direct connection of the pick-up, it should be considered that the sound produced could be too open to listening, with many highs, not very damped and at that point we would no longer have the possibility to intervene directly from the instrument.
As for the values of the potentiometers, except for individual choices, potentiometers from 250 Kohm for pick-up a single coil e 500 Kohm for the humbuckers.
These values have been determined to have the best relationship between the possibility of regulation and the cut of high frequencies introduced by the potentiometer.
Another choice is between potentiometers linear e logarithmic.
Generally, the volume pot is logarithmic while the tone pot is linear.
Capacitors used in guitar tone circuits usually have values between 0,02 and of 0,05 uF.
In relation to the construction material, the capacitors can be in: paper and oil, Polypropylene, ceramic...
I don't specifically go into the construction and interfacing of volume and tone controls because this would pave the way for a new article on the subject and become highly distracting. The best thing is certainly to rely on quality components that are well interfaced in terms of resistance and capacity with the pick-ups used.
The pickup selector as well as the jack socket they must be of quality and proportionate to the value of the instrument. In fact, as well as being mechanically reliable and long-lasting, they must be excellent conductors, trying not to hinder the passage of the signal and not to introduce variations in listening.
Height adjustment of the pick-up
We have seen that the positioning of the pick-up is of fundamental importance, but its height adjustment can also play an important role.
A pickup very close to the strings will generate a more volume but also a less sustain, due to the greater magnetic attraction on the string, which thus tends to block it in its movement.
Instead, moving the pick-ups away from the strings will result in a sound more balanced and truthfulness of the instrument.
However, by moving it too far away, in addition to a low volume, we run the risk that the vibration of the string is no longer able to disturb the magnetic field well, thus generating a sound without some characteristics.
Numerous articles have also been written on the adjustment of the height of the pick-ups and often the manufacturers of the instruments, depending on the characteristics of their pick-ups, give the right positioning advice.
Another consideration that we can insert at this point is that of the sonic characteristics of a single coil pick-up compared to a humbucker.
Keeping in mind what has been explained in the two articles so far, and well aware that generalizations often do not reflect reality, we can report what appears to be a common opinion, namely that Single coil pickup generally have a more open sound e defined, with clear highs, a stronger attack and alower exit.
In contrast, the humbuckers have a more "hot"/"thick", Less defined and with a 'highest exit.
I would stop here with the generalizations for what was written above and for all the variables that come into play in the construction of a pick-up.
It will seem obvious, but in this brief excursus the strings must necessarily be mentioned.
As is known, electric guitar strings must be made of metal so that they can interact with the magnetic field of the pick-ups.
The greater the ferrous mass that vibrates, the greater the perturbation to the magnetic field and the greater the volume of the induced signal. For this reason electric guitar strings are built using steel (an alloy mainly composed of Iron e carbon, the latter as a maximum percentage of 2,14%) And the nickel (belonging to the iron family) in various combinations.
The choice of scaling, of the type of winding and of all those parameters and characteristics that every musician looks for, will be linked to personal taste and to the musical genre played, even if we must be aware that in the case of the electric guitar the strings, in addition to playing an important role in determining the “acoustic” sound of the instrument interact directly with the magnetic field generated by the pick-ups.
Tailpiece-for-guitar
Often, in fact, changing one pack of ropes there is a need for a fine adjustment of the pick-ups.
At this point, we have seen how pickups play a fundamental role in building the sound of your instrument. However, we are also aware that they work in conjunction with a whole host of other factors.
We must first remember that the pick-ups will capture the sound produced by the instrument, which will have its basic sonic characteristics.
The constructive choice of / our / a bass / guitar will therefore be fundamental so that there can be a certain sound; for example:
- Type of woods for the the body: alder, ash, poplar ...
- Type of woods for the handle: maple, mahogany ...
- Type of woods of the keyboard: maple, rosewood, ebony ...
- Construction type: glued or screwed handle, fixed or mobile bridge, wood thickness, wood seasoning, body top, ladder ...
Eventually the sound of an instrument will be the combination of more or less determining factors.
This is the good of it!
Even within a very high construction standard, two guitars may be similar but not identical, especially when natural elements such as wood are also used in the construction. Each piece of wood is a unique and unrepeatable piece. So two similar guitars, while having a sound that will be superimposable for the 99%, they will probably never sound perfectly identical.
If we add to this the taste and personal preferences… everyone will look for his instrument.
Good music to all
Bibliography
Musical instruments N° 116
Musical Instruments N ° 193
Musical Instruments N ° 194
Musical Instruments N ° 195
Musical Instruments N ° 196
Helmuth Lemme: Electric Guitar Sound Secrets and Technology
Dave hunter -The Guitar Pickup Handbook: The Start of Your Sound
Wikipedia
Agreement.it
Build your Guitar.com Helmuth EW Lemme The Secrets of Electric Guitar Pickups
