Looking for custom made toroidal inductors

Do you know any manufacturer that would make custom one off toroidal inductors for equalisers ?

I know a few sources for standard core inductors, but for toroidal type I have only found vintagewindings and they are in USA, someone based in Europe would be preferable.

beatnik said:

Do you know any manufacturer that would make custom one off toroidal inductors for equalisers ?

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Gowanda Electronics has made inductors for clones of  UA model 500 equalisers.
They performed as good as the originals.
https://www.gowanda.com/

Try to contact GDIY member "Moby" , he's making transformers but recently he did some inductors for Pultecs.
He lives in Serbia.

Have you tried asking your local transformer manufacturer? You'd be surprised how much most of them are capable of these days, if you just know exactly what you want..

That said, I still wind my inductors myself. Not toroids, but need to select for cores and tune before final assembly. For tolerances obviously.

Jakob E.

Thanks for the suggestions.

When building stereo units, what should be the tolerance of the inductors ?

what circuit?

beatnik said:

Do you know any manufacturer that would make custom one off toroidal inductors for equalisers ?

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When you say one off do you mean just one inductor or a low quantity (after initial sample) ?

beatnik said:

When building stereo units, what should be the tolerance of the inductors ?

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Usually I would aim for somewhere around 1% for broad filters, ½% for the sharp'ish ones.

But very much depends on what you are trying to achieve - don't over-design, as precision in inductors gets VERY expensive quickly, once you're over some 10mH or so..

Jakob E.

gyraf said:

don't over-design, as precision in inductors gets VERY expensive quickly, once you're over some 10mH or so..

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What about it contributes to the cost? Labor, materials, both?

Toroid is just a core shape. What type of core material do you plan to use?

Cheers

IAn

beatnik said:

Do you know any manufacturer that would make custom one off toroidal inductors for equalisers ?

Click to expand...

Why specifically toroidals? Is there any property of toroidals that justify your choice?

When building stereo units, what should be the tolerance of the inductors ?

Click to expand...

Typically the tolerance on inductance reflects by half on tuning frequency; 5% tolerance on inductance reflects as 2.5% tolerance on frequency.
How audible it is depends very much on the actual BW of the filter.
With a 1-octave wide filter, the most  difference in response is on the slopes of the graph, accounting for about 0.5dB at half and twice the tuning frequency.
With narrow filters, again the most difference is on the slopes; however, since it is usually tuned to a frequency of interest, the difference there may be more perceptible at the center frequency.
You may experiment with a parametric filter; on narrow settings (used for pinpointing a specific frequency), the tuning accuracy is more sensitive than the side-effect of changing slightly the tonal balance below and above.
Indeed, fixed inductor based EQ's are not particularly adequate at pinpointing narrow frequencies, so you may be more concerned with tonal balance issues.
When I made inductor-based graphic EQ's, QC was pass at +/-2% on frequency. Those bands that did not pass would be reworked by changing or adding caps.