Under THe Hood HumbuckerKnow-How
What’s behind the Doubletap humbucker concept and how is fender wiring up its performers? let’s take a look…
The new DoubleTap humbucker, as its name suggests, is a slightly different take on a humbucker-to-single-coil split. Basically, what we have is two slightly mismatched coils. Using the neck humbucker on the Sunburst Telecaster Hum as the example, the screw coil measures 4.26k and the slug coil measures 3.88kohms. Additionally, the screw coil is tapped: namely, a second ‘start’ wire is added after around half of the wire is wound onto the coil, which means between the tapped ‘start’ wire (white) and the finish wire of that coil (black), we get a reading of 2.6k. When the coils are linked in standard series humbucking, Fender uses that tapped start of the screw coil, not the full coil, and that tapped coil (2.6k) is joined in series to the full slug coil (3.88k), giving a reading of approximately 6.48k.
When you pull up the tone control switch voicing the single-coil mode, the slug coil is dumped to ground and the full untapped screw coil is voiced, giving us that reading of 4.26k.
Fender is shouting about this being a Patent Pending design, but prior art would surely include the pickup development we’ve seen from Paul Reed Smith, from the 2011 Signature model through to the 408 and the Custom 24-08 guitars. In the UK, Alan Price at Catswhisker Pickups has been offering the S-Bucker, which uses a similar concept. However, what both of these do – which is different to the Double Tap – is to use a tapped portion of one coil to boost the output of the other to create a stronger single-coil voice. Fender is trimming the output of one coil, in series mode, but then voicing that full coil in single-coil mode.
As to the concept of tapping a coil, in either a humbucker or single-coil pickup, well, that has been used by numerous makers: Tom Anderson, Joe Barden, Seymour Duncan and PRS (back in the day as well as in the present) spring to mind with little thought.“Yes, I was doing it back in the 70s,” DoubleTap designer Tim Shaw tells us.“In fact, Bill Lawrence showed me how to do that in 1973, although I think Bill liked the series/parallel thing better because it stays humbucking, but to me it doesn’t sound as cool.”
It does mean, however, that you could wire a DoubleTap in a few ways: most obviously as a hotter 8.14k series humbucker. Conversely, due to a malfunction on the rosewood Tele Hum when we received it, its slug coil was shorted to ground, so in the ‘humbucking’ mode (with switch down), it voiced just the full screw coil, and, when you pulled the switch up, it voiced the larger 2.6k tapped portion of the same coil, which sounded good. The neck- and bridge-position DoubleTaps might “have the same parts-count, plus the cover on the Tele Hum, but they’re quite different”, relates Tim.“The Tele humbucker had to play nice with the bridge pickup we’d already done. Now, as you know, if you just put a stock humbucker in that position it’ll just blow the bridge pickup away, and you’re loading that pickup because you’ve got a 250k pot in it. So, the neck DoubleTap on the Tele Hum has an Alnico 5 magnet, whereas the bridge version on the HSS is Alnico 4.”
And while that bridge DoubleTap uses the same tapped coil concept, our sample was wound a little hotter, approximately 7.74k.“The winds kind of serve the position, so I did what I needed to do to get them to play nicely with their friends,” confirms Tim.
“On the humbuckers, we didn’t use shellac [for potting],” he continues,“because it’s impossible to clean off the plastic [of the uncovered bridge DoubleTap], so those are wax potted, but the coils only. Some people will wax the entire pickup under vacuum; these are the coils only.”
Unlike the American Professionals, the Performers’ circuits are more traditional in that they don’t use a treble bleed circuit on the volume controls. Pull back the volume on the Strat, then, for example, and it’ll subtly pull back some of the crisp highs. Tone 1, used for the neck and middle pickups on both of our Strats, uses a conventional 0.022 microfarad capacitor, whereas tone 2, used on the bridge pickup, has the Greasebucket circuit on its own small circuit board with surface-mount components. The original Greasebucket circuit uses a 0.1 microfarad cap across the input and wiper lugs – the same position that you’d put a cap on a volume for a treble bleed – then a 0.022 microfarad cap and a 4.7kohm resistor are wired in series from the wiper to ground. It gives a different effect: the roll-off sounds less bass-heavy or choked and works very well with crunch and gain to darken but retain some clarity.
Both Strats also have the same HSS body routing, so you can easily swap scratchplates loaded with either SSS or HSS pickups. And, hopefully, we’ll see not only those ClassicGear tuners, but also these Yosemite and DoubleTap pickups in the Fender parts shop sometime soon.