Passive EQ inductance calculation

[dustbro]

Hello All!
Does anyone have experience calculating inductance in a passive EQ? Trying to figure out the windings on a UA508B EQ.
I've calculated:
46mH, 46mH, 23mH, 14.9mH, 11.5mH, 5.7mH, 3.7mH
It appears that the total inductance is 46mH, but I don't understand how the first 2 windings would measure the same.
Also, since this inductor is in series, would the calculations be additive?
ex:
???, 32.1mH, 13.9mH, 9.1mH, 5.8mH, 2mH, 3.7mH
Thanks in advance!

 

[PRR]

> I don't understand how the first 2 windings would measure the same.

If you want an Octave spread, and are not switching the caps, and both coils are snugged on the same core, you want two identical windings 46mH each or 184mH coupled together.

> would the calculations be additive?

Separate core would be additive. Common core goes as *square* of number of turns, so "46 & 46" becomes 184.

 

[gridcurrent]

Universal Audio 508b inductor


DC resistance inductance and Q @ 120 Hz inductance and Q @ 1000 Hz



coil # 1 41.08 ohms 6.242 mH @ .113 5.128 mH @ .695


coil # 2 21.76 ohms 1.977 mH @ .066 1.585 mH @ .412


coil # 3 14.95 ohms 1.028 mH @ .050 .825 mH @ .311


coil # 4 22.96 ohms 2.694 mH @ .085 2.025 mH @ .479


coil # 5 13.05 ohms .978 mH @ .052 .7205 mH @ .307


coil # 6 38.12 ohms 11.33 mH @ .217 7.589 mH @ .87

 

[dustbro]

Thanks guys!
@gridcurrent  Can you tell me how you arrived at these figures? Trying to learn