Using Transformers as inductors?

[hodad]

Specifically I'm interested in the possibility of using them as EQ inductors. I know you can use transformers as inductors, and there would appear to be more than one approach to it, but I'm mostly curious as to what the issues with doing so might be. And what about with little cheapies like this thing? https://theelectronicgoldmine.com/products/g26936a?mc_cid=3655ce389d&mc_eid=0601f8e528

 

[abbey road d enfer]

Well, you may want to try. There are many projects that use transformers as simple inductors. The most common issues are the variability of inductance from one to another - ou may see about -50/100% tolerance - and excessive losses.
It really depends on the level of performance you want to achieve.

 

[scott2000]

Specifically I'm interested in the possibility of using them as EQ inductors.

posted about this in another thread in the past....maybe useful
https://www.talkbass.com/threads/acoustic-320-graphic-eq-repair-3h-inductors.810974/

somewhere there is a list of the values... I'll try to look for it but it's around that area of talk.....

here it is
https://audiokarma.org/forums/index...placement-coil-inductors.995445/post-15594654


just seeing this too....
https://groupdiy.com/threads/sourcing-audio-inductors-in-2022-for-equalizers.81989/post-1130226

 

[hodad]

and excessive losses.
It really depends on the level of performance you want to achieve.

Excessive losses might be a concern--is a transformer likely to attenuate the signal more than a purpose-built inductor?
At this point I'm just interested in experimenting, so performance doesn't need to be impeccable.

 

[abbey road d enfer]

Excessive losses might be a concern--is a transformer likely to attenuate the signal more than a purpose-built inductor?

No, just may skew the frequency response and add distortion.

 

[gyraf]

..for quick prototyping, I've always used transformers as substitutes for large'ish inductors..

 

[capacitorless]

I'm also intrigued by this for use in a passive eq topology. Is there any benefit to putting components on one side of a transformer, when the other side is in use as an inductor? I'm thinking of whether it could fine tune the response, introduce non-linearities (if desired), that kind of thing.

For that matter, could simply putting DC across the non-used side do anything beneficial?

 

[abbey road d enfer]

I'm also intrigued by this for use in a passive eq topology. Is there any benefit to putting components on one side of a transformer, when the other side is in use as an inductor? I'm thinking of whether it could fine tune the response, introduce non-linearities (if desired), that kind of thing.

For that matter, could putting a current across the non-used side do anything beneficial? (I'm way tired and not thinking clearly, and I haven't thought this through comprehensively, so apologies if this is an obvious no-go )

Putting a DC current in a winding results in lowering the inductance of all windings.
That's how magnetic amplifiers work. They used to be the system of choice for high power motor drives (think rolling mill).
Distortion is very high.
OTOH putting a capacitor across a winding reflects as a bump in impedance for all the other windings. That's what is done in many oscillators.

 

[deleteduser]

OP, this is a great idea and makes different things possible than using inductors alone: example. differential orientation of transformer, rather than the regular way. now you could play with +/- in a new way which is beneficial.... ie.... I built this thing that was pretty cool: it allowed you to bump up the - excursion more than the +, such that the speaker diaphragm would move further into a speaker box, than forward. this allows for more symmetrical motion of the speaker, "whereas normally" the pressure inside the cabinet will always reject the diapragm with a tendency. worked pretty cool for me. nice little mastering trick. I think yours is a great idea. I Wouldn't wire up a transformer as a regular inductor, probably, because its a little more difficult to make a transformer than an inductor in the first place, and would be kindof a waste. series, parallel, phase cancellation, split stage, single stage... might all be possible with a transformer rather than an inductor... which is cool. But I'm thinking ... you have a normal two coil transformer... and on the input you have this inductor going to ground, and on the end of the circuit at the output you have an inductor to ground, and you have this sortof coupled inductive filter going on or something. YMMV.

 

[abbey road d enfer]

OP, this is a great idea and makes different things possible than using inductors alone: example. differential orientation of transformer, rather than the regular way. now you could play with +/- in a new way which is beneficial.... ie.... I built this thing that was pretty cool: it allowed you to bump up the - excursion more than the +,

Do you mean the inductance varied with the current direction? That's news for me.

such that the speaker diaphragm would move further into a speaker box, than forward. this allows for more symmetrical motion of the speaker, "whereas normally" the pressure inside the cabinet will always reject the diapragm with a tendency.

The displacement dissymmetry is not due to air pressure, it's due to the suspension, which indeed has assymetrical compliance.

 

[deleteduser]

Do you mean the inductance varied with the current direction? That's news for me.

oh no sorry I see what you mean its so hard to type and be breif and make sense at the same time. I guess I was just saying if you imagine a transformer oriented differentially, rather than conventionally, (and then added independent wipers on each coil for varied series impedance...) That is curious though. for some reason this made me think of "cancelling" magnetic fields... like those inductorless wirewound resistors I wonder if there is some funny circuit using that principle or something.

 

[gyraf]

imagine a transformer oriented differentially, rather than conventionally, (and then added independent wipers on each coil for varied series impedance...)

does not compute