Pickup Lines
Amp designer and pickup winder Hayden Minett of Bulldog Pickups brings the rocket science of pickup electronics back down to Earth…
DC resistance is a common reference with respect to the imagined sound and response of a pickup. In truth, however, with a complex set of interactive variables at play, the sound of your guitar depends on far more than just ohm readings alone.
“DC resistance is a very useful gauge of output power – with a few caveats,” says audio engineer Hayden Minett. “You have to make sure you’re comparing apples with apples. You can use DCR as a pretty good indicator of output power if the pickups you’re comparing have the same wire gauge and magnet type. If they have, it will always be that the higher DCR pickup is louder than the lower DCR pickup. Changing the magnet affects it, but it’s the wire gauge that makes the most significant difference.
“If you think about a piece of wire, it has a resistance. And if you make that wire thinner, the DC resistance goes up. For
“Guitars are generally high impedance and high impedance is prone to interference and signal loss”
example, say a humbucker wound with 42 [AWG] wire yields a nominal 8kohms. If you wind the same pickup with the same number of turns using thinner 43 [AWG] wire, it’ll come out about 10kohms. The two will be roughly the same in terms of volume level, but there will be a noticeable tonal difference. The 43 AWG wire will probably sound a bit brighter, thinner and not overly pleasant. But if you increase the number of turns what you’ll find is, eventually, you’ll get the body of the tone back and it’ll start sounding usable. And that’s the approach people adopted back in the early days of DiMarzio and [Seymour] Duncan. It was all about thinner wire gauge but more of it, because it gives you more power and a full tone if you get enough turns on.
“Coil size, wire gauge, coil shape and so on all determine the frequency response of the pickup. The problem with DCR as a comparative tool, however, is that the published figures aren’t necessarily comparative between brands, so I tend to avoid it. On the other hand, when resistance becomes impedance in an AC circuit then the maths suddenly gets quite complicated and the concept starts becoming a little harder to understand. But, ultimately, you’ve got to try and match the impedance of the pickup to the impedance of the amplifier in AC terms.
“In the case of a valve amp, the input impedance is governed by the first valve and the load resistor – that presents a load on the pickup. If you change the load on the pickup, it drastically changes the characteristic of the tone you get. A typical input impedance mismatch – with your high-impedance pickup going into a low-impedance input – equates to poor tone response. Guitars are generally highimpedance devices (obviously it’s different with the Gibson low-impedance pickups or anything active) and high impedance is notoriously prone to interference and signal loss. You can hear the result of different impedances by plugging your passive pickup/guitar into the high and low inputs of an amp; the difference in tone and volume is all down to this relationship. The other thing is when you turn the guitar volume control down – that also changes the load on the pickups, so you’ll start to hear subtle changes in tone as well as volume.
“The pickup also has capacitance and inductance from the coil, which work against treble. The ‘resonant peak’ is the point at which the capacitive and inductive effects converge, giving a peak in output response. This can also be affected by things like the input impedance (or load) of the amplifier input and the resistance and capacitance in the cable. In practice, a higher resonant peak means the pickup is more efficient at the brighter end of the tonal spectrum, which is typical of lowerpower vintage-style pickups. Scatter-wind techniques can help reduce the capacitive effects and increase the resonant peak.
“There’s a hell of a lot more to pickups than DC resistance. But beyond that, what really matters is if you like the sound!”