Factors affecting how your guitar pickup sounds…
ALNICO = ALUMINUM NICKEL COBALT MAGNETS
Characterized by excellent temperature stability, high residual induction, and relatively high energies. These were the first materials specifically designed for permanent magnets to be used in meters and instruments commercially.
Alnico is vailable in both cast and sintered forms. Sintered Alnico offer slightly lower magnetic properties but better The Alnico (Aluminum, Nickel, Cobalt) family was introduced in the 1930’s. It’s mechanical characteristics than cast Alnico. These materials are brittle, hard and cannot effectively be machined by conventional techniques other than by grinding.
It is often said that ceramic magnets are brighter than alnico, but that isn’t entirely correct. What makes a magnet “brighter” than another is it’s strength. A stronger magnet will be brighter. Because ceramic is so much cheaper than alnico, Alnico in grades above 5 (or 8) is rarely ever used.
CuNiFe magnets (A alloy of copper Nickel & Iron) are rarely used now either as they are so rare & expensive and sintered modrn ALNICO can substitute as it can be milled
High output pickups often use ceramic magnets. Ceramic magnets are actually weaker for a given grade/size after a certain point.
Some magnets are rubberised eg; SS Ry Cooder magnets.
In the sizes used for pickups, Alnico is weaker. A pickup which utilizes Alnico pole-pieces can have different poles made of different strength magnets to accentuate or minimize certain characteristics.
Pickups which have a bad sound or string may have a magnet which is not matched to the others; rarely one polepiece will actually be upside down.
Demagntization factors- some say alnico will degausse/de-magnitize if ground or filed due to the heat. As the maximum “practical operating temperature for alnico is 540*C (1004*F). I don’t think you’ll get it that hot with a file or a grinder…
**BUT don’t lean your guitar against speakers etc with big magnets inside them you will degausse your guitar pickups
The finer the wire the fewer highs pass through. Finer wire also has a higher resistance for a given length. For this reason a pickup wound to 6k with 43awg wire will have less output than a pickup wound to 6k using 42awg wire. Regardless of what has been said I do not believe there is any difference based upon type of insulation alone. However, wire with a heavier insulation (i.e. “double build”) will result in a wider coil at the same resistance/output. The “shape of the coil” effects the magnetic field
Shape of the coil:
A coil which is taller and narrower will be clearer, more focused and slightly brighter than another coil which is shorter and wider if they have the same output. Filtertrons have higher slender bobbins so the coil shape is taller & narrower.
The shorter wider pickup & coil is sensing a wider section of the string, which gives it more variance in the signal it’s sensing (due to variance in oscillation size/ pattern of the string along the length of string sensed)
There is a characteristic of wire called “skin effect” which is more pronounced in smaller diameter wires due to their higher resistance.
“Skin effect” is where the higher frequencies travel along the surface of the wire rather than travel through the centre of the wire. This leads to that “brittle” characteristic of high output pickups which must be wound with the finer wires…
Number of windings:
The greater the number of windings the greater the capacitance and inductance of the pickup. Because of this more low bass end is generated along with an increase in output. Additionally, more windings will make a slightly wider coil, see “shape of coil” effect above.
If a pickup has a metal baseplate or cover, and it is grounded, some of the highest frequencies will pass to ground by a means called “flux line coupling”
Metal base/ cover:
If the plate is magnetic, and not grounded it will increase the capacitance and inductance of the pickup much like more windings do. The metal will also add lows/mid lows.
How the magnet(s) are placed has an effect on the field of the pickup and therefore the signal generated. An example of this is a P-90 type pickup which has the polarity of the magnets repelling each other in comparison to a similar pickup with the polarities attracting each other. The opposing polarity pickup seems to be less focused. The slug magnets are also pointing at the strings unlike a bar magnet laying inside a pickup under say the bobbins
Some say Alnico weakens with age, and this relates to magnet strength as previously explained. (Magnet manufacturers claim a loss of strength at a rate of aprox .2-2% / 100yrs) However, some manufacturers are “aging” magnets by heating. They have found through testing that this type of “aging” does NOT weaken the magnet (there is a point at which it will, but it’s almost an “all or none” situation) What it does do is “temper” the magnet (alnico) relieving internal stresses. Testing has shown that before tempering there was often an unevenness of strength between magnets of the same “rating”, i.e.Alnico 5, even between the two poles of the same magnet. The tempering almost always equalized the strength of the two poles of the same magnet, and lessened the variance between magnets of the same rating. However, it was not uncommon to still find some variance (I believe significant). For this reason we now have all alnico magnets tempered and test them for strength.
As a side note, information provided by a magnet manufacturer indicated that tempering in this manner will make the magnet less susceptible to outside interference.
Much of the characteristics which are attributed to the aging of the magnets may actually be due to the aging of the coil wire. This makes more sense based upon tests and experience, and what is known about magnet aging. The older insulation (formvar and enamel) will get hard and brittle with age, this would also “stiffen” the coil windings, changing their characteristics slightly. Also note that the older “Lacquer potting” on some pickups tends to break down significantly with age. This will have a definite effect.
Machine wound pickups have a very even wind pattern; custom wound, hand wound and very old pickups generally have a much less regular winding pattern. This is called “scatter-winding”; what happens is every time the wire crosses, the flux line generated also crosses and couples making one larger irregular flux line. We believe this causes the pickup to react as one large “whole” instead of more like many finer flux lines interacting with and reacting to each other. I believe this is why handmade/ scatter-wound pickups almost never have “brittleness” even if they are bright, scatterwinding and the flux line couple helps destroy the “skin effect”.
Besides breaking up “skin effect” it also causes something called “distributed capacitance” which is where the capacitance of one winding is spread to other windings within the coil. Scatter-winding causes the capacitance to be “spread” across many more windings. It also minimizes “mutual (self) inductance” which is where each individual winding picks up and amplifies a portion of signal from adjacent windings.
We at RED Herring partially pot our ‘tone-bones’ with 100% paraffin wax as beeswax is acidic and reacts with copper baseplates no matter how organic it sounds!
if you dont want potting we dont pot…or can pot VERY minimally eg HUMbuckers!
Let us start by saying this is all subjective and we don’t fully understand everything here (well, I don’t have any hard data to back it up)…First off, a properly wound pickup doesn’t usually need potted (fact). An un-potted pickup is going to be more “musical” than an unpotted one if its wound properly; however, it will also be more prone to damage and will wear out more quickly.
A pickups windings actually move with vibration as the electro-magnetic field moves and with the body vibration to a small extent. That’s why light to un-potted is more musical, however if the windings are too loose the pickup can be microphonic, even to the point of picking up your voice (I suspect the voice somehow causes the windings to move ever so slightly). Potting prevents the vibration and thus eliminates the risk of microphonics.
The harder the potting material the more “high fi” the pickup will sound. Thats why epoxy potted pickups are often considered sterile, but this lack of overtones helps those same pickups stay defined in very high gain situations. Also, the potting material will effect the pickups “resonant peak” and can actually change the point and frequencies at which the pickup “breaks up” or feeds back.
Now, what is often called “microphonics” isn’t, it’s a pickup squealing or feeding back due to a loose part somewhere, any air gaps between surfaces can vibrate and cause the squealing, very often it’s the pickup cover. It’s also a common problem w/ tele bridge pickups because the copper plate underneath becomes loose. Potting fills the voids and prevents vibration hence stopping the squealing. From a production standpoint, it is just too easy to have problems without potting especially if the pickups are going to be used in a very loud/ very high gain environment, so most pickups are potted from the factory (the “good ones” anyways, there are a few exceptions) RED Herrings latest solution is a “partial potting” of the coil, only isolating the outer windings and allowing the inner ones to move..
Most of these factors are not huge on their own (in general, magnet strength being one exception, it’s pretty significant. Coil shape /size is another). But combining them will have a significant impact on how the pickup sounds. All of these factors must be considered and balanced when trying to achieve a particular “sound”. It is easier to start from a known point, and make minor modifications to that than it is to “start fresh” because there are too many interactions going on to determine “which” factor(s) made the difference.