Wah Inductors. No hype. Just measurements.

Regarding the Crybaby inductors measuring close to the Fasels, Dunlop manufactures the Fasel inductors themselves and they started using them in their wahs years ago from what little research I did before I built my Shamwah. My donor unit was a 535Q and it's inductor was one of those metal enclosed inductors. I never thought to test the resistance at least with my multimeter.
 
Yeah, Dunlop basically bought the name.

So: I need to learn a bit more is what I'm finding. Seems like inductors will tend to be frequency-dependent, yeah? So the TC-1 probably tests at one frequency, and the LC at another. Or is it voltage dependent? Shit, I gotta get a better handle on this.

I know that inductance in AC signals tends to have the opposite effect of capacitence: inductance results in voltage leading current. The magnetic properties induced resist the flow of current when current is passed through the inductor. Beyond that I'm fuckin lost.
 
So, ok. Wrapping my brain now.

  • Inductors are not frequency dependent.
    • However, Inductive reactance is.
    • This measurement is generally given in ohms.
    • It is defined as an impedance, rather than as a resistance
  • Inductors are very similar to capacitors, in that they're opposites, for the most part.
    • Fuck you, that makes sense.
  • Caps store energy as an electric field.
    • A capacitor initially appears like an open circuit when power is first applied.
    • As voltage rapidly increases across a cap's terminals, current to and from those terminals decreases.
    • With AC, the electric field will charge and discharge. The timing of this is governed by the resistance of the circuit times the capacitence.
      • This is the RC time constant.
  • Inductors store energy in magnetic field.
    • And inductor Initially appears like a short circuit as power is applied.
    • As current flow rapidly increases across the inductor's terminals, voltage drop across those terminals rapidly decreases.
    • With AC, the magnetic field will charge and discharge.
    • The timing of this is governed by the resistance of the circuit times the inductance.
      • This is the RL time constant.
So...what does that all mean? It means that capacitors resist changes in voltage, and inductors resist changes in current.

Cool. So those are some of the basics.

Now I gotta read more.

*Edit: ok. Now I've read more*

Capacitors exhibit capacitive reactance, which will increase in resistance as frequency *decreases*, as capacitors resist changes in voltage.

Inductors exhibit indictive reactance, which will increase in resistance with as frequency *increases*, as an inductor resists changes in current.

The capacitor will have more time to recover, that is to charge and discharge it's stored voltage with lower frequencies, which impedes the transmission of lower frequencies.

Still trying to wrap my head around Inductive reactance, honestly. It sounds like it essentially is able to smooth out higher frequencies into a more "stable" waveform because they resist changes in current flow. The fiber points of how of the magnetic field that does this works eudes me though.
 
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Maybe reading up on inductance of electric motor windings will connect a few dots?
Things like why the inductance of the windings naturally smooth out the stepped output of a VFD.
Here's some text books if you must

Lessons In Electric Circuits

A free series of textbooks on the subjects of electricity and electronics. By Tony R. Kuphaldt.
www.ibiblio.org

Or more pointed to the topic

Lessons In Electric Circuits -- Volume II (AC) - Chapter 3

Reactance and Impedance -- Inductive
www.ibiblio.org
 
jwin615 said:
Maybe reading up on inductance of electric motor windings will connect a few dots?
Things like why the inductance of the windings naturally smooth out the stepped output of a VFD.
Here's some text books if you must

Lessons In Electric Circuits

A free series of textbooks on the subjects of electricity and electronics. By Tony R. Kuphaldt.
www.ibiblio.org

Or more pointed to the topic

Lessons In Electric Circuits -- Volume II (AC) - Chapter 3

Reactance and Impedance -- Inductive
www.ibiblio.org
Click to expand...

Yup. This is my speed. Commercial HVAC mechanic, after all.

But AC induction motors have an important difference: a rotor with an induced magnetic charge.

As the magnetized rotor passes over the poles, it creates back electromotive force. Back EMF isnt generated in a simple inductor, so decoupling the two ideas has been a bit of what I've been working on for the past few days in my free time.

Learning process. Hey, I went to college for psychology and switched when I realized that you could hit a machine with a wrench when it didn't behave the way you want it to without having any tense conversations with law enforcement afterwards.
 
giovanni said:
This is cool. It would be nice to compare to some commonly available transformers that are sometimes used instead of inductors.
Click to expand...
I have tested most of the common wah inductors against generic Chinese 1:1 isolation transformers and found that they read much closer than you would think. But more importantly they often sounded better to my ear with only the highest end ones not losing to the cheap transformer.

I’ve also tested random NOS chokes and variable inductors against wah ones, and random old transformers to their modern counterpart. Results here are more mixed / to taste.

Did all this several years ago and wrote it down, I’ll have to dig it up and post it maybe revisit it now with better equipment
 
han-tyumi said:
Did all this several years ago and wrote it down, I’ll have to dig it up and post it maybe revisit it now with better equipment
Click to expand...

For sure. Would like to see what you've got.

Honestly, though, my purposes here are more inclined towards objective findings - measurements - rather than what sounds good on a subjective level.

Though right now I'm just focused on inductance and resistance measurements.

The transformers I've tested thus far tend to have greater resistance measurements than the inductors. I'm also curious as to how the differences in materials effects things here: RG Keen's article on wah pedals makes mention of the wahs of old having inductors with potentially impure cores that may have held a magnetic field.

The theory went that, after some time with current passing through the inductor, the core would become partially magnetized. This magnetized core would act against the magnetic field induced by the inductor, which would cause some asymmetrical clipping when the inductor was driven hard.

It seems to me that a cheap transformer may use a more impure ferrite or even an iron core. That would certainly be more susceptible to permanent magnetization.
 
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