Vox wah wah mods

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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?
 
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.
 
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?
 
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.
 
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.
 
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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
 
replacing the 10nf cap on Q2 with a 3 way switch i started to play around with different value caps to try and establish a working range which i could choose 3 values within.
1nf seemed to hi, and 120nf seemed too low, so i used 10nf, 22nf and 15nf.
10nf to 22nf seemed pretty good but the 15nf wasnt so noticable, so i will try 5nf, 10nf and 22nf. 10nf definetly works just nice to have two other options.
 
Did some tests today

Found out that the max voltage that the inductor will see is about 35 millivolts p to p at resonance, regardless of input signal levels and frequencies, so saturation of the inductor, no matter which one you use, is probably not going to be a factor. The wah circuit limits the output amplitude of the upper and lower frequencies above about 3 k hz and below about 200 hz to about 80 millivolts, so a low frequency signal large enough to saturate the inductor will never occur do to this voltage limiting. When the output level is sitting at 80 millivolts, the inductor voltage sits at about 5 millivolts or less.

Saturation might be a factor at 100 hz if you had a good level across the inductor, but the circuit prohibits this.

I plotted some response curves at three different frequencies, 367 hz which was the rez freq at pedal up, 816 hz which was rez freq at pedal in the middle, and 1.98 k hz which was rez freq at pedal down.

Output at resonance with a 50 millivolt RMS input signal was about 440 millivolts RMS at all three test freqs.

The Q of the curves at the three freqs was steeper at the 367 hz signal freq and flatter at the 2 k hz in freq.

This got me thinking of a possible mod, a dual 100 k pot.

One would be wired as usual, at the output signal part of the circuit, and the other would be wired into the tank circuit so as to vary the Q of the wah wah as it was being played.

What say?
 
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Did some tests today

Found out that the max voltage that the inductor will see is about 35 millivolts p to p at resonance, regardless of input signal levels and frequencies, so saturation of the inductor, no matter which one you use, is probably not going to be a factor. The wah circuit limits the output amplitude of the upper and lower frequencies above about 3 k hz and below about 200 hz to about 80 millivolts, so a low frequency signal large enough to saturate the inductor will never occur do to this voltage limiting. When the output level is sitting at 80 millivolts, the inductor voltage sits at about 5 millivolts or less.

Saturation might be a factor at 100 hz if you had a good level across the inductor, but the circuit prohibits this.

I plotted some response curves at three different frequencies, 367 hz which was the rez freq at pedal up, 816 hz which was rez freq at pedal in the middle, and 1.98 k hz which was rez freq at pedal down.

Output at resonance with a 50 millivolt RMS input signal was about 440 millivolts RMS at all three test freqs.

The Q of the curves at the three freqs was steeper at the 367 hz signal freq and flatter at the 2 k hz in freq.

This got me thinking of a possible mod, a dual 100 k pot.

One would be wired as usual, at the output signal part of the circuit, and the other would be wired into the tank circuit so as to vary the Q of the wah wah as it was being played.

What say?
show and tell me more and i will make it so!!!
i'll even do a video, ive got some dual 100k here
 
Maybe a resistor in series with the pot like 10k, then try swapping outside leads to get more q and less q depending on the pedal travel,

I have a dual 100k audio pot, just finished jb welding the gear on there, had to mill out the cutout 1/8 inch to accommodate the extra depth of the pot. Will wire it up tomorrow,

Note: since the inductor operates at voltages in the noise floor range, perhaps a mu shield would be a good mod, all those turns act as an antenna, Crybaby's have never been the most quiet things in the world, although toroid's and ferrite pot cores are supposed to be hum resistant,
 
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Just wound a inductor with some 0.05mm gauge wire on N48 and has ended up at 86ohms, very similar spec to castledine inductor and the bottom end is much improved and the overall sweep seems to be wider and more even.
More resistance it seems is better for the N48 ferrite, must dampen the low end more?

 

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