One customer recently asked if our pickups incorporate a dummy coil, here's our answer.
In the usual sense a dummy coil is merely a second pickup or a remote air-cored coil in series or parallel with the main pickup that is sensing the strings, the dummy one being positioned away from the strings so there is no string sound being picked up. When two active pickups are connected in series it is commonly said to produce the sound of a humbucker (dull and lacking brightness and far less expressive). The same sound results when a dummy coil is connected in series, it's because the capacitance of each coil combine and the result is like rolling the tone control back. Dummy coils may cancel hum but they also destroy the sound quality.
Kinman's approach is to minimize capacitance of both coils so it never exceeds that of an ordinary single coil, and often it's far less.
Boss Chris Kinman invented and patented our Differential Coil technology and it is used in every Kinman pickup except our humbuckers, but will even be there soon too (in our multi-sonic Converge-3).
So what we have is 2 very different coils, the upper one is the string sensor and it is optimized to produces the best string signal and it also produces unwanted hum. The lower one senses ONLY hum because there is a patented magnetic shield made from special silicon steel that isolate the 2 coils from each other and without that the hum sensor would also produce string signal and that's a bad thing since any signal in common is cancelled between the 2 coils.
That's what's wrong with stacks and sidewinders and is the reason they sound so awful. Both coils are identical and both produce hum and string signal and both are cancelled (but because of the proximity effect the string signal is less in the lower coil and therefore it is not fully cancelled).
For maximum immunity to hum *all the time* the hum sensor ideally must be the same size and orientation and as physically and electrically close to the pickup as possible, like our pickups are. Integrating our hum sensor with the pickup produces several synergistic electro-magneto effects that boost efficiency. Boss Chris found that remote dummy coil hum sensors, like the large air-cored dummy coils, are prone to some hum when the guitar is pointing in other directions than optimum (which is most of the time) and hum comes and goes. That's one of the many reasons Kinman Zero-Hum pickups are superior.
Our hum sensor is designed to be 3 to 5 times more efficient than the string sensor so we can wind it with thicker wire and fewer turns thus minimizing parasitic coil capacitance, but it is calibrated to produce the same hum voltage as the string sensor and therefore hum is fully and perfectly cancelled. Thicker wire and fewer turns means it is a highly transparent coil and has negligible impact on the string signal as it passes through. There are other secret proprietary technologies that we use to maximize the desirable sonic characteristics provided by this ingenious hum cancelling mechanism. Also it allows us to make great sounding pickups that cancel hum which still fit into guitars. An ordinary dummy coil attached to the bottom of an identical pickup makes the whole thing far too tall and will not fit into guitars without cutting the cavity deeper, and why would anyone want to destroy the sound of the pickup anyway?
So yes, in a way you might say our hum sensor is a dummy coil ,,,, but it's no ordinary dummy in the usual sense that it is just another pickup identical to the one that senses the stings ,,, no sirreee!!! That kind of ordinary dummy pickup system impacts negatively on the sound way too much, robbing expressive dynamics and tonal characteristics from the sound of the pickup in much the same was as connecting pickups in series.
Boss Chris started out trying to perfect a dummy coil system way back in the 1980's but he found so many insolvable problems with that technique that after 10 years of trying and failing he eventually abandoned the concept as fatally flawed. He persevered and went on to bigger and better things and eventually invented and patented a whole new concept based on a new way of thinking about dummy coils. Navigate to >About Us >My Story ,,,, and read a fascinating and inspiring story about how this all happened. It's a really good and entertaining read.
above) Our patented high efficiency 600 Ohm Laminated Steel hum sensor bobbin from our Telecaster bridge pickup.
above) Ultra High efficiency 600 Ohm hum sensor bobbin from our Gen-2 P-90 Hx. Our Gen-3 v2 hum sensor is even better.