In the final installment of a four-part series for Mojotone’s tech-savvy readers, we explore the many enigmatic specifications that play a part in any pickup’s sound and performance.
Many guitarists quote specs the way baseball fans quote statistics.
Sometimes these can come together to provide some indication of how a piece of gear will perform—and in this case, a given type of pickup—but there is almost always more to it than the numbers can fully relate. Purchasing a set of pickups and installing them in your guitar with hopes of achieving a desired sound requires a massive leap of faith, so it’s totally understandable that many players hope to achieve some measure of advanced assurance by applying known specs, materials and construction techniques to the quest. To get anywhere with such efforts, however, we need to understand what the specifications really mean (and perhaps more importantly, what they don’t). The most important stats relating to pickups can often help us paint a rough picture of how they will sound, relative to others of the same type at least, but misapplying these same numbers will too often lead to disappointment in our tone-tweaking efforts.
Given the above considerations...
Part 4: Spec Check seeks to provide an in-a-nutshell view of why different pickups sound and perform the way they do, but only when considered alongside the many significant factors explored in the first three parts of the series. So, consider this one the icing on the cake, providing a real-world means of handling the specs that you will often see attached to these devices.
Please note, also, that there is simply no scope in an article of this length (or that of any articles in this mini-series) to provide a comprehensive “tone guide” to all the individual pickups out there: search the number of pickup makers working today, large and small, and multiply that by the number of different models they offer and you’ll quickly understand how futile such an exercise would be. Even the best effort to do so would only risk leaving out the specific pickup that you happen to be interested in. But that’s the very point of this four-part Introduction to Pickups series from Mojotone: learn the important factors, components, designs and specifications relevant to any type of pickup, and you’ll go in with a decent understanding of how it is likely to sound.
Resistance and Impedance
One of the most often-quoted specs for any pickup is “Resistance,” which is the measurement of a coil’s opposition (or “resistance power”) to a DC current, measured in Ohms. The same measurement of an AC component is called “impedance”, and it is also recorded in Ohms. As quoted in the specs sheet of most commercial pickups, the stated resistance implies that it tells us something about how “powerful” the pickup might be, although there’s more to it than that. For a Stratocaster pickup, for example, it might say 6.2k Ohms for a somewhat vintage-voiced product (where “k” means “times a thousand”, or 6,200). The conundrum in all of this is that standard electromagnetic guitar pickups create an AC signal, but we tend to measure only their DC resistance, simply because this is easier to do. As such, these specs that proliferate pickup-makers’ web sites don’t do the full job of telling you how hot or powerful any pickup is; they do, however, go some way toward helping you build up a picture of the pickup’s characteristics, once you know some other details and have several relative factors with which to compare it.
Essentially, any pickup’s resistance measurement just tells you how big the coil is—that is, how much wire is wound around it—or how big the two coils combined in series are if it’s a humbucker. The trouble with using this as a set standard, however, is that different gauges of wire yield different resistance readings for the same given length. Thinner wire gives higher resistance readings in most instances because you can wind more around it than the thinner gauges of wire. The resultant pickup might not produce a greater perceived output despite the higher spec, but you can be fooled into thinking such pickups are “hotter”. The fact is, two otherwise similarly constructed pickups will not only sound different because of the different wire used—say, 43 AWG vs 42 AWG—they will give very different resistance readings as well.
To give one example, this contrast applies to many replacement Telecaster bridge pickups that makers produce as “Broadcaster pickups,” using 43-AWG wire like that which Fender used in some of its earliest guitars. These can often yield DC resistance readings upwards of 10k ohms, which makes them appear particularly hot on paper when viewed alongside Telecaster bridge pickups otherwise wound with 42-AWG wire to a vintage-correct spec of around 6.5k to 7.5k ohms. But these Broadcaster pickups usually don’t sound dramatically more powerful than the 42-AWG pickups. They do, however, sound a little different in other ways.
In addition, many of the more thoughtful pickup makers will tell you that “resistance readings mean nothing”...
when trying to gauge the sound of any pickup, and for the most part they’re right. They do mean something, however, if you know all the other factors in a pickup’s design and construction and are using specs for resistance merely as a gauge to judge likely nuances between one pickup and others that are constructed identically in everything other than coil size (ie length of wire used). To that end, any weight given to resistance readings should be considered in light of all of the other things we have examined in the previous three installments of Introduction to Pickups. With that in mind, this spec might help to get you somewhere. For example, consider six similarly designed PAF-style humbuckers, made with the same materials. Attach six different DC resistance readings to these, and you can guess that the 6.85k-Ohm pickup might sound a little thin, bright and under-gunned in the bridge, but snappy and round in the neck; the 9.2k ohm pickup is likely to sound a little too fat and muddy in the neck, but will be meaty and thick in the bridge, and so on, with all sorts of gradations in between.
But generalizing more broadly about a wide range of pickups’ power, or so-called “output”, by using DC resistance as a yardstick can be misleading. A pickup’s resistance doesn’t measure anything being “put out” at all, but is a static measure of its coil at rest, taken with a specially designed meter, and simply reads the length of X gauge of wire that has been wrapped around the coil. Greater or fewer turns of wire in a coil of a specific design will yield a more or less powerful result, respectively, but comparing the resistance readings of a Strat pickup, a Tele pickup, a Gibson P-90, and a Gretsch Filter’Tron will get you nowhere. Even if all read exactly 6.5k ohms you can guarantee they will all sound very different, and even exhibit distinctly different output levels, driving your amp to varying degrees.
To get a fuller specs-based picture of how any given type of pickup might sound relative to others of the same breed, we can consider resistance on conjunction with “inductance”. The Concise Oxford English Dictionary tells us that inductance is “the property of an electric circuit that causes an electromotive force to be generated by a change in the current flowing.” So much for the pure science—what does that mean in terms of tone? Inductance is measured in a unit called “Henries”, and to put it in perhaps overly simplified terms, such a reading tells us how “fat” a pickup will sound. As a general rule, the higher the inductance, the more restrained the high end, and the thicker the mids and lows.
While resistance is a pure measure of how much of any given gauge of wire is wound around the coil, however, inductance can be affected by other things.
Unusual or irregular winding patterns, metal components in contact with the magnet and coil structure, and other factors can all raise a pickup’s inductance above what the raw coil might read on its own.
To provide some examples, the average Stratocaster pickup will have an inductance of between 2 and 2.5 Henries, while the average traditional PAF-style humbucker will register something above 4 Henries. The average Telecaster bridge pickup, on the other hand, will read a little over 3 Henries. Fewer pickup makers provide specs for inductance than for resistance, but it’s something that more and more people are aware of, and you can usually find it if you poke around, or simply ask.
As with all other specifications, though, shopping according to inductance readings is only likely to disappoint or confuse your efforts to achieve the pickup that’s right for you. In conjunction with all of the other factors we have discussed, however—coil type and wire gauge, magnet type and position, general pickup design and construction, and resistance—it gets you further toward an understanding “on paper” of how that pickup might perform relative to others that are similarly made. The only real way to know how any pickup sounds, of course, is to put it in your guitar and play it.
Hopefully these four installments of Introduction to Pickups, taken together, will get you somewhat closer to identifying and finding the ideal pickups for your own personal tone. Happy hunting!