Vox wah wah mods

[Spencerleehorton]

I’ve just wound a n30 4.6uh core I have two inductance meters one which tests at 100hz and the other at 202hz.
I’ve wound it so it comes out at 510mH one 100hz and it reads 530mH on the other.
Sounds pretty good in the wah but I wondered whether there was an easy way to test to find the Q?

 

[abbey road d enfer]

Would like some advice on working out Q factor of inductor.
I have found the calculation but wanted to check I’m doing it right, might invest in a lcr de5000 at some point but would like learn the old school way of number crunching first.

2 pie (6.28 x frequency x inductance / resistance)
My inductance meter tests at 202 hz
And inductance is 500mH and it’s 30 ohms

So is it:
6.28 x 202 x 0.5 / 30 = 21

?

Your calculations are academically correct, however when you see CJ's post #140, it's all over the place when you change the level and frequency of measurement.
In addition there is a loss factor, that is similar to a resistor in parallels, which is also variable, so a single figure cannot describe the whole behaviour of a physical inductor.

 

[Spencerleehorton]

Yes I get that I have to measure at different frequencies and plot a graph, just wanted to know the correct way to get a full understanding.
I’m assuming I will need to measure over the 100hz to 10khz to show where it peaks but what level is ideal? Or is it just inductance and frequency graph?

 

[abbey road d enfer]

Q is a single figure that's useful for describing the general shape of response, but when it comes to details, the fact that inductance varies with frequency distorts the shape of response.
It's just a starting point.

 

[CJ]

The ac voltage across that coil will depend on the note being played and the position of the pot, not much voltage above and below resonance.

 

[Gus]

The wha patent from 1967? is one of the best things to read and understand if you want o build/adjust whas like the type in this thread