[John Byrns]

In article ,
Patrick Turner wrote:

On May 31, 1:09*pm, John Byrns wrote:
In article
,
*Patrick Turner wrote:

On May 29, 11:23*am, John Byrns wrote:
In article ,
*John L Stewart wrote:

Before this thread went off the rails did anyone mention that
McIntosh
uses a seperate winding on the OPT for overall NFB?

A separate winding, a tertiary winding, provides better high frequency
stability
than taking the NFB from the secondary winding. *The down side of using
a
tertiary winding for NFB is that the NFB doesn't include the secondary
so
that
the damping factor suffers, this probably has no practical consequence,
but
doesn't make for good ad copy.

Yes but the NFB winding position relative to anode turns or secondary
turns will have an effect on what is fed back.

Yes, the design/positioning of the tertiary winding affects the leakage
inductances between the various windings

I'd say that if a fine wire NFB winding is wound right over the top of
a thick wire speaker secondary then its signal is near equal to the
speaker's signal and the "error" made by the secondary Rw and LL and
phase shift et all is fed back for correction.

No tertiary can correct for the "Rw" of the secondary!

I'm not so sure. if the tertiary is wound close to anode coils, sure,
Sec Rw is not reduced by NFB. But if tertiary is wound close to Sec, a
drop in sec voltage gives a drop in tertiary voltage, and a FB signal
corrects the drop, no?

NO, even if the tertiary were perfectly coupled to the secondary, it still
couldn't compensate for the secondary winding resistance.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/