Air coil inductor in "tin can" 3120 X-over

[Mannermusic]

I managed to snap off one of the leads (the inner one, natch) to the 1.4 mH coil in one of my old 3120 crossovers. Can I replace it with an air coil or is there a "flux environment" effect caused by the iron enclosure which would affect the air coil differently than the iron core inductor? Assume you would want to change both sides to keep the resistance balanced, etc. What's the crib? Thanks, Mike. :dont-know

[Baron030]

Hi Mike

Ok, if I am following this straight. You need to replace the 1.4mH coil in a 3120 crossover. And you are considering an air core coil as its replacement. But, you are concerned that the iron enclosure will throw off an air core’s inductance value.

I would have to say that your concerns are correct. The iron enclosure will throw off an air core’s inductance value. One solution would be to mount the air core coil outside of the enclosure far away from any ferrous metal. But, if you really want to keep everything inside the enclosure, then I think you would be better off with an iron core.

In looking at 3120 network, you are really lucky in that you didn’t snap a lead off of that 1.1mH tapped coil. That’s a part that would be very difficult to replace.

Baron030 :)

[Mannermusic]

Thanks a lot guys - you verified my suspicions. Will see what I can scrounge up - or, as you say, the 3120A is actually a more capable unit (although I have to admire the clever simplicity of the 3120 circuit). Had to laugh at the "hang it outside" comment - you should see my cobbled setup. That's a good way to run evaluations as well - one test is worth 1000 expert opinions! Thanks again. Mike:D

[Mannermusic]

The final solution was to rewind the coil. Will add some longer leads so the top can be removed easily. Love that goop - wonder who thought of that, what a mess. Mike

[Maron Horonzakz]

I thought the can was aluminum ,, But i can be wrong..:blink:

[Mannermusic]

I thought the can was aluminum ,, But i can be wrong..:blink:

The 3120 and similar are all Fe alloy - 1010?. The earlier Signature crossovers we all grew up with - N2400, etc. - are "potmetal", similar to a carburetor body (Zinc alloy of some variety). I actually tried a magnet on the enclosure before making this post - wouldn't have bothered otherwise. Seemed a questionable choice of materials to me. Mine even had some rust inside. A miniature humidore of sorts. And then there is the sticky goop . . .

[Maron Horonzakz]

I think your right,,,, it seemed kind of brittle.