tweaking inductors

[PeteMcK]

I know this may be a dumb idea, and the purists will react with horror, but is it possible to tweak the value of an inductor by partly introducing a small piece of ferrite into the gap, sort of like tuning IF transformers in a superhet....????????

Another dumb question, does an inductor wound on a ferrite toroid behave differently to one wound on ferrite bar?

Pete McK

[Ron E]

If you are going to go to that trouble, why not just make a multitap inductor?

Yes, toroids are different from rods or bobbins, the ferrite mfg will tell you the design equations. There aren't a lot of toroids made for use in speakers, and buying bobbins and winding your own is probaby more expensive than buying ready-made.

[johninCR]

You can easily tweak an inductor, at least downward in value. Just take off some windings. If you wanted to increase it, you could splice in some varnished wire and add windings.

[rabbitz]

Reminds me of installing a inductor that's wound on a plastic bobbin. If you use ferrous fasteners, the inductance value can go up if the fastener protudes into the centre of the coil. Non ferrous fasteners are a better choice.

Maybe it's a way to tweak with different diameter and length ferrous fasteners screwed down the centre of the coil........ don't know if it's any good for the sound though.

[sreten]

Originally posted by PeteMcK
I know this may be a dumb idea, and the purists will react with horror, but is it possible to tweak the value of an inductor by partly introducing a small piece of ferrite into the gap, sort of like tuning IF transformers in a superhet....????????

Another dumb question, does an inductor wound on a ferrite toroid behave differently to one wound on ferrite bar?

Pete McK

1) A sliding core is just about the easiest way to adjust
inductance, I can't see any problems using it to reduce
the inductor value.

2) Absolutely, the toroid has far more inductance
and it is much easier to saturate the toroids core.
A ferrite bar is like an airgapped toroid opened out.

sreten.