Transformer question: Bifilar windings in series

if you wind a secondary bifilar and put the coils in series you get a step up ratio of 2. but the interwinding capacitance is strange if you think about it. especially into an unbalanced load. Equitek power conditioner people claim that a balanced power isolation transformer wound this way has outstanding balance. I am assuming with a grounded center tap in their case. and then of course the classic API output is trifilar? if i remember correctly, with 2 sections in series as the output. Ive wired api's without the step-up but am not sure if it sounds different. Any opinions, suggested reading?

mike p

> bifilar and put the coils in series ...the interwinding capacitance is strange if you think about it.

So don't think about it, it won't be strange?

If capacitance matters, you don't do bifilar.

Bifilar is a trick for LOW impedance windings where capacitance is not the dominant parasitic.

> power conditioner people claim that a balanced power isolation transformer wound this way has outstanding balance.

I strongly suspect the primary and secondary are not bifilar to each other. If they have two bifilar 120V secondaries and you stack them to split-240, everything balances. There is extra capacitance to ground on each live end; that's not objectionable in a 50/60Hz power transformer both because of low-Z and slightly desireable because we don't want anything over 60Hz.

[quote author="PRR"]
So don't think about it, it won't be strange? [/quote]

are you implying that there may be a quantum mechanical effect at play here?

[quote author="PRR"]
If capacitance matters, you don't do bifilar.
[/quote]

the way I see it, as long as you don't need isolation, the inter-coil capacitance of a bifilar pri-sec just helps extend the bandwidth. can be a good thing in a 1:1 line output.

anyway, the application I had in mind has significant DC current going into the center tap. a bifilar winding in series would ensure very well matched turns and L in the two halves, so the flux will cancel to a high degree and a non-gapped transformer with high-perm core is used. cheap and easy to wind compared to fully interleaved, especially to get the DC to cancel.
I was wondering if anyone had a subjective general opinion of how a transformer wired like this "sounds". like the sowter 4652 wired primaries in series, secondaries in series

mike p