About Pickups

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About Pickups

Post by oldstrummer » August 19th, 2016, 7:30 am

Can anyone point me to a resource that will educate me on guitar pickup technology? I've played mostly acoustic, and those electrics I've played have never given me reason to think about replacing the pickups on them.

But I know nothing. The word "humbucker" has been around forever, and it sounds like it's designed to reduce/eliminate the electronic hum that can be generated from electronics, but other than that, I know nothing. And I could be wrong about humbucking.

Now I'm thinking of swapping out a stock pickup that sounds too "tinny" to me for something else. But what?

How do I know what kind of pickup produces what kind of sound? And how they work with a guitar's wood, electronics, etc?

I am truly clueless about this aspect of guitar. So, thanks in advance for your putting it into plain language (if that's possible).
Duke Ellington said it best: "If it sounds good, it IS good!"

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Re: About Pickups

Post by bassman302 » May 1st, 2017, 10:14 pm

I'm an electrical engineer-- I'm going to do my best not to lose ya.

The American power grid runs on 60Hz Alternating Current (AC) power. Every transformer that steps down the voltage from the electric utility to the usable low voltages (120V, 208V, 277V, etc) also runs at 60Hz, as a result. The power transformer in a tube amplifier also runs at 60Hz.

The basic structure of a pickup is a plastic (or other material) bobbin with some magnets loaded into it and many turns of almost-hair-thin (usually 42 or 43 AWG) copper wire wrapped around it, creating a "coil" of copper wire. The problem is that this coil of copper wire makes a fairly-decent antenna, and is likely to pick up that 60Hz electromagnetic field all around us. This 60Hz signal can propagate through your guitar and amplifier, manifesting itself as a 60Hz "hum" sound. This is called "60-cycle hum."

A Humbucking pickup solves this problem by making a SECOND pickup like the first one, only with two crucial differences:

1) The copper wire is wound in the OPPOSITE direction. If the copper coil from the first pickup acts like an antenna, then the copper coil from the second pickup acts like a REVERSE antenna-- the result is that the waveforms generated by each coil are traveling in opposite directions and cancel each other out (a phenomenon called "destructive interference")

2) The Polarity of the magnets are reversed. As I said, just above, the coils are conducting wavelengths in opposite directions. This is also true for the magnetic field generated by the pickup's magnets. Thus, if the magnets were the same polarity, your sound would also suffer from that waveform cancellation I described above. To solve this problem, the second coil in a humbucking pickup reverses the polarity of the magnets, which induces a waveform in the same direction as the waveform produced by the first coil. So, instead of canceling out the waveform from the first coil, the second coil actually ADDS to it (within certain frequencies)! Yet, because the coils of copper wire are wound in opposite directions, EXTERNAL electromagnetic interference, like 60-cycle hum, still (mostly) cancel out!

So that's humbuckers...

As for tone...

Single coils (think P-90, stock Fender Strat and Tele pickups, etc) tend to have more "twang" in the sound. Remember how I said humbuckers cancel out 60-cycle hum? Well, it also cancels out some of the high frequencies.as well, though the midrange tends to be more pronounced. Because a single coil does not have any of that waveform cancellation, it will tend to have more detail in the treble frequencies. The downside is, of course, 60-cycle hum.

Humbuckers, as I just stated, tend to have more bass and midrange "baked in". However, they can be all over the map, tone-wise. A "Filtertron" humbucker by the Gretsch guitar company tends to retain a lot of treble, due to some interesting workarounds (using less copper wire while doubling the thickness of the magnet, among other things). Many of the popular "Hot Rodded" pickups based on Gibson's humbuckers have a thicker midrange.

Don't worry much about the wood. Tonewood is definitely important in an acoustic, far less so in an electric, unless you're a salesman trying to convince a customer that a certain wood will make a big difference in tone. In all actuality, the fact that each species of wood has a different resonant frequency means there could be a small effect on your tone, but your strings and pickup choice have a much greater effect.

When you're researching pickups, you will probably find DC Resistance (usually in Kilo-Ohms) ratings for the pickups. Don't worry too much about them-- they don't mean as much as a lot of people think they do.

You see, when electrons are conducted by a copper wire, the electrons do not travel INSIDE the conductor, but on the surface of it. The longer that wire is, the more RESISTANCE the electrons have to work against in order to travel from point A to point B and back again (remember that sound is a wave, with positive and negative magnitudes). Also, skinnier wire has less surface area than thicker wire, so this also increases the coil's resistance.

In essence, the higher the resistance, the fewer electrons are traveling through it.

Also, if a pickup has a higher resistance, it will likely produce less treble, since treble frequencies are higher frequencies (thousands of cycles per second, instead of dozens or hundreds), requiring the electrons to move back and forth through the copper coil many more times per second.

So why would anyone use more wire when doing so rolls-off your higher frequency response?

Greater inductance (stronger signal, or "more power", even though we are talking about voltage, not power).

You see, each turn of copper wire increases the strength of the magnetic field. The stronger this magnetic field, the greater the voltage the coil induces. This voltage is what travels to your amplifier, which converts those small changes of voltage in to large changes of current, which drives your speakers.

To recap:

* A higher DC Resistance value means the pickup contains either more turns of copper wire, or is using thinner copper wire. The end result is usually less treble, with more focus on the midrange. A higher resistance also hints at the possibility of being a stronger pickup, but not necessarily.

I did the best I could to put this into laymen's terms. If you have any questions, feel free to ask.

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Re: About Pickups

Post by hthiew » May 3rd, 2017, 6:58 am

Bassman302 did an awesome job explaining the technical aspect of the answer to your question.

I'll do a simple one.

If the pickup sounds too thin, as Bassman302 have mentioned, the thicker sounding pickups are P90s, mini humbuckers or humbuckers. It will depend also on the slot your current pickup is in. If its a single coil sized pickup, you may not be able to get a P90s and the humbuckers into the slot. However, there are humbuckers that are made specially to fit into a single coil slot eg. blade pickups such as Seymour Duncan Hot/Coil Rails.

I'm answering your question assuming you are talking about your electric guitar pickups. If you mean an acoustic pickup, then there are sound hole mounted pickups in both single coil and humbucking kind.

Having said that it may not be that single-coil pickups have to sound thin. Sometimes it may be the stock cheaply made (usually ceramic) pickups and poor engineering that causes the sound to be hollow or empty. There are quality single coils (like those by Fralin and Lollar) which uses more expensive materials like alnico magnets making it fatter and more vintage sounding.

Just my 2 cents. Hope others can chip in with more info about this.

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