[AMRadio] Class AB and B audio XFMRS

W5OMR/Geoff w5omr at satx.rr.com
Sat Mar 11 18:28:16 EST 2006

Jim candela wrote:

>John E. Coleman (ARS WA5BXO) wrote:
>>	I have been doing some experimenting here on the side and have found
>>a interesting thing that I've seen before but forgotten about.  I thought I
>>might share it here with you guys.
>Geof W5OMR Wrote:
>I can't believe that no one else has replied to this, on the reflector.
>From: "Patrick Turner" <info at turneraudio.com.au>
>Subject: Re: SE Output transformer design idea
>Date: Monday, August 25, 2003 8:06 PM
>Jim WD5JKO pasted in the following:
>This from an old thread about single ended audio transformers, and how some
>folks deal with the high DC flux from the class A audio output tube. In many
>respects this is the same problem we AM'ers face with push pull modulators
>where the mod transformer has to bear the RF final plate current without
>core saturation. Pay attention to the stuff about using a DC constant
>current source into one winding to buck the flux from the Class A output
>tube plate current. It may not be practical, but it sure is interesting...

What I surmise about their discussion is that they've basically came to 
the same conclusion that John has...

More iron is better.  For us, that means we need more iron at the Class 
B Modulator level.  All of the Henries of reactance wont matter, if the 
modulation transformer iron isn't suffiecient enough.  Not necessarily 
for passing low frequencies.. rather, having enough iron in the 
transformer, to not have to worry about cross-over modulation, ergo, 

Good post, Jim!  I enjoyed it, and am looking for more.

73 = Best Regards,

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