Inductor for Guitar (TL021)

[Natman]

Hey all,

I have been wanting to experiment with variations of the midrange cut per Rothstein/Torres circuits. I ordered up some 42TL021 from Mouser, which is a tiny choke/transformer, NOT marketed as an inductor per say (but it is used by many Varitones and the midrange cuts mentioned). They usually use just the primary.

I saw a schematic online where somebody connected one end of the primary to the secondary, I presume to increase the inductance? Found it:

Is there any merit to doing this? It seems to me that the windings would induce a magnetic flux in the core that would cancel each other out? If it is valid, I might try it...

Thanks for your input!

[cbarrow7625]

If they are connected in series and in polarity (summing), the inductance will increase somewhat. If they are connected on opposite polarity, it will reduce the inductance. The spec sheet doesn't list the inductance, just the resistance, so i can't tell you for sure how much/less. I'm not sure what wiring would constitute in/out of polarity either.

Hopefully there will be enough of a difference that you can hear the notch shift up (lower inductance) or down (higher inductance) in frequency while connected in series to a cap. Get that figured out & you might be able to get 3 useful notch filter tunings without even changing the cap (Primary only, plus in series with secondary in/out of polarity - but the three may only be subtly different). Give it a shot. Love to know if it is worth the effort.

[bbsailor]

The inductance of the 42TL021 increases by 440 additional turns when the secondary is put in series and in phase. The additional 440 turns represents a 30 percent increase in turns count. To calculate the inductance increase, just represent this increased turn transformer as 1.3 and square this number to get 1.69 and this 1.69 represents the inductance increase by adding 440 additional turns.

I hope this helps?

Joseph J. Rogowski

[Steve A.]

I have heard of humcancelling inductors used in guitars. Depending on how you connect the two windings here you might have some hum cancellation (only some because the coils are so different.)