being an electrical engineer myself for over 20 years I'm quite interested in the subject.
Cool! what discipline of EE?
As I said in my earlier post all of them are factors, but being a PU a pair of coils the main factor in it is its inductance, since it is an inductive circuit, not a capacitive one.
Capacitive, inductive, both play a role and since we are primarily concerned with how it is applicable to AC it is a "reactive" circuit. Inductance alone cant determine everything, it is merely one piece, or one note of the triad (did I just go there?, that was dorky!)
That's one of the reasons pole piece material and shape as well as some extra metal in the coils like the DMZ V V technology have such an effect in the sound of PUs. You don't see manufacturers tinkering with caps inside PUs for that same reason,
Well one reason: internal inclusion of a physical capacitor is not really practical nor discrete
- not exactly an easy thing to physically include/encase. two that being said, and like I said earlier inductance is the easier of the three parameters to physically control within the case size without affecting the other three, and more importantly one you can be sneaky and discrete about
. you have a couple of choices, you can increase inductance by increasing turns, which means you have use thinner wire, for the same physical coil size, but this as a side effect also more drastically changes the other two of the three parameters, both DCR, and capacitance increases which also affects the resonance peak frequency and q, - it's not so easy to control this way, you traded one for the other. by comparison, increasing more surface area, or more metal, you can effectively increase the inductance for a given coil without increasing turns, or resorting to thinner wire to do so.
although you could use them as filters like other guys around here to mod the TZ.
Being so is the reason some manufacturers publish inductance values for their products but none of them publish capacitance values. The most common published figure is the resistance values as it is a figure most people can relate to and can measure with equipment easy to have access to, not the case with inductance since it requires a very specific meter, like the Extech LCR meter which is commonly used by boutique winders for quality control of their products and experimentation.
True, most publish the DCR as it is the most easily relate-able to the end user, and an easy test for anomalies or partial shorts but this is probably by the same token the most useless parameter to give an idea of how something is behaving in context especially if we are talking about reactive context, and MORE importantly how it sounds musically!. It doesn't tell you a whole lot in reality by itself, just as much as the DC resistance of a speaker tells you. Most inductance meters will also just measure DC inductance which is no use to us, it will be several times higher to AC.
Capacitors in a tone control don't increase "composite winding capacitance", they just shunt highs to ground and the pot controls how much of the original signal you send through it.
what does AC really see's in this scenario? (small signal ac really does apply!) the pot controls how much of the cap is isolated from the coil, the fact that ts grounded is irrelevant. the resistance between the cap, and the coil retards the caps effect because to AC the resistor is still the higher impedance path, since to anything above the reactive time constant created by the cap and resistance the cap looks like a dead short (one of the reasons tone controls load your signal by virtue of being connected). what happens when the pot is fully clockwise?, the capacitor is in parallel directly across the coils.
I can simulate this part in spice if you wish and post the results, if you think it will help others or the cause at all since the small signal AC will hold up well in sim. not necessarily the losses part due to materials though, which is not so easy for. The TZ bass mod is not exactly the same thing, that Is just a simple first order high pass filter because of it's position.
In fact, the tone control cap is isolated from the capacitance of the windings by the value of the tone pot itself in the most common wiring used.
Not as easy as that, you have to examine what AC REALLY see's in this scenario through various sweeps in the pot, which is not as cut and dry.
Please explain more about the real life complications on this matter,
Sure. You touched on it yourself, its not as cut and dry. the physical properties make a difference as do the materials used. magnetomotive properties of the assembly have an effect on the real life empirical result as you mentioned, especially regarding tone which is what we are concerned about really. I have seen some actually measure the losses in the brass base plate dimarzio uses, and have deemed it a contributing factor.
