Study of Pickup Characteristics Collaboration with UIUC

[Hugh Evans]

It's been a busy past few months for me, and I hope to have some more information on the CNC coil winder design I've discussed here before. However, as a byproduct of my coil winding project lead me back to my interest in more thoroughly studying physical properties and their effect(s) on output signals. Extensive work has already been conducted by the physics department at UIUC (University of Illinois Urbana-Champaign) so I decided to contact the professor behind said research. Thus far they have been limited to pickups that have been purchased or borrowed, but the specific details of their production such as winding pattern and tension are unknown. A collaboration has been proposed in which several pickups are wound covering several permutations and then double blind tested using the existing rig at UIUC. Test design will determined with one active professor, potentially one emeritus professor, and a couple of undergrad volunteers will be found to carry out most of the testing and data analysis.

Since this collaboration is in very early stages, I figured this would be a great place to look for any additional input on parameters worth exploring. Their test procedure already includes magnet strength and orientation, DC resistance, capacitance, inductance, real and imaginary impedance curves... and that's all that's needed to calculate the rest. My initial thoughts are to vary winding patterns, tension, AWG, and magnets. All experimental results are planned to be made freely available to the public, although setting up a fund raiser to cover material costs has crossed my mind. The goal as I see it is to make duplication of a pickup's response a much easier task with less black magic involved. In the longer term, coming up with a cost-effective system for testing/verifying pickup response would be a great tool (the guys at UIUC have really nice toys to play with.)

Anyways, I'm more than a little bit excited about this project. Any input is welcome.

[Mike Sulzer]

Any input is welcome.

Sounds like a great project, Hugh. You have not mentioned the need to account for the metal parts of the pickup on the measured impedance versus frequency curves. There are audible effects as well, IMO, but it would be very useful to perform DB listening tests.


Impedance measurements showing the effects of these eddy currents (an effect first brought to the attention of the forum by Joe Gwinn) are discussed here:
Measuring pickup impedance with an A/D recording interface

[bea]

The effects of the construction immanent eddy currents and ferromagnetic components of the construction should also be considered in some ways. They seem to have an important effect on the sound. Consider, for example, the mudbuckers (sidewinders) and other constructions with more or les laminated steel between the bobbins, the dark star.

BTW: i recently determined the resonance frequency of an epiphone bass sidewinder to 3.1 kHz (modified by additional steel blades and two additional alnico magnets, but that should even lower the resonance).