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Peter Daniel 5th July 2005 04:42 PM

Pirmary over secondary in a toroid
I'm planning on ordering some custom toroids for GC (from Europe) using amorphous core.

I have here a Definitive Technlogy toroid (from Apex Jr) with primary done over the secondary windings.

I was wondering if there is any specific advantage for audio, winding transformers in this way. It definitely produces less inrush current, and the sound is very good, but does it indeed have much advatnatge (or disadvantage) over more coventional methods of transformer winding?

Leolabs 6th July 2005 01:54 PM

If u r looking for a low inrush current stuff,stick to the old EI.Tell us what they talk about thier special winding method.

richie00boy 6th July 2005 02:37 PM

They were probably just mistakenly made :D

Vidalgo 8th July 2005 08:18 PM

Primary, when winded over secondary, have a more resistance - that why inrush current is lower.
Such traffo need a very good outer insulation.
It must be really hard - wind thick wire first, around rectangular shape (assuming core is not so-called "R-core").

jleaman 8th July 2005 08:53 PM

peter you should try one of these.

steenoe 8th July 2005 09:00 PM


- that why inrush current is lower.
I think this is right, I have an old "donut" ,made like this! It is smoother at startup than any other torroid I have tried! I didnt initially think it was because of the windings, but this might be the answer :)
I am not totally confirming this, though. But what else could it be?


Magura 9th July 2005 12:54 AM

AFAIK such way of winding also brings magnetic shielding issues to the table. I have had one of those and ditched it cause it made everything around it noisy :(

Magura :)

Peter Daniel 15th September 2005 01:24 AM

2 Attachment(s)
So I ordered 2 pairs of transformers: one with secondary on the outside, the other with primary over secondary, both with amorphous cores.

The one with secondary closer to the core sounds better (to me).
No issues with a noise either.

Those are 300VA units with 50% larger dia. secondary wire.

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