Magnetic Transducer Design

[separateness]

Does any one here know about (or know of any resources pertaining to) pickup design? I understand how they are constructed and function and how the inductance of a coil is calculated, the form and meaning of models of a pickup as a second order low pass filter, and even one or two other things. What I am unclear on is how to take a design goal (a given inductance, DC resistance, and maybe parasitic capacitance), go about choosing a geometry, core/magnet material and size, wire gauge, number of wraps and realizing it in an existing magnetic transducer.
Most online discussion of pickup construction seems to revolve around recreating or riffing upon proven designs and it seems that what I have in mind is as far I can tell without precedent in musical instrument pickup design (perhaps for good reason).

 

[gyraf]

Pickups are many, many things.. are you thinking of guitar-pickups maybe?

 

[separateness]

Well, much like a guitar pickup only it would only need one slug and the goal is to have a very low resonant peak, below 100Hz. I can determine the RLC values that will give me this, but I lack a work method to go from this to a plan for the construction thereof. I suppose I could plug values into the coil inductance formula until I found a right combination which would render the desired inductance and DCR, but that seems rather crude.
If there are no such books or other resources on developing pickups and brute force is the only option, then I suppose there is my answer.

 

[gyraf]

I have a feeling we have a XY problem here - The XY Problem - can you explain what you are trying to do, and why?

/Jakob E.

 

[separateness]

I would like to build a pickup transducer with an inductance of around 5 Henries but a DCR of only about 350 ohms, I will add an external capacitance to give me a nice resonance in the low frequencies. I would like to do so for the purposes of percussion-like sound creation. Further, and more importantly, I would more generally like to know the process of deriving a plan to build a pickup from any given design goal (eg if I would like to build a pickup whose resonance occurs at f frequency with a Q of some given value). I am not sure how my initial question did not cut directly to the heart of the matter as I do not care to be spoonfed what turns, core, geometry etc to use but would much prefer to be able to find them myself.
I have ventured to guess, as best as I can, that one must decide on on a frequency response and from that derive inductance and resistance, then from that determine through arithmetical experimentation geometry, core, and turns which will render the sought inductance and lastly to choose a wire gauge that will yield the desired resistance with the given coil.

 

[gyraf]

for the purposes of percussion-like sound creation

..you do realize that whatever this pickup+eq combination will do, can as well be accomplished by a linear pickup followed by a resonator stage? Look e.g. into the good-old analogue drum machine audio generation (yes, we used coils for those)

But for your question: once you know your intended core material and -shape (which will be determined by what you want to pick up), you can measure it's A(L), then the number-of-turns gives itself, plus-or-minus a bit in the winding geometry that might give or take a bit of stray capacitance (but as you're aiming for huge-resonance somewhere low-freq, and will add parallel capacitance anyway, this part is probably insignificant)

/Jakob E.

 

[separateness]

A regular pickup followed by a tank circuit is probably the most rational, reasonable and logical way forward, it is true. I have looked a bit into early electronic percussion (I have a particular fondness for the Wurlitzer Sideman), but have seen none that do as you say. As far as I can tell, most or all (Pollard Syndrum et al) seem to use piezos as triggers to set off an active damped oscillator of some kind, whereas I would like to actually use (part of) the signal generated as the sound itself.

As for choosing a core first, I suppose that is the only reasonable way to proceed, and one must just sort of ballpark it, knowing the L and DCR they are aiming for, what sort of core will likely give them the desired result. Thank you very much.