[AMRadio] 75TH vs. 75TL (was Class C stuff)

[w5omr]

: Don't overlook the fact that not only is the bias requirement  different, 
: but the audio voltage swing requirement at the grid is also different.  The 
: TL reqires a much higher audio voltage at the grid than the TH does, while 
: the grid current will be less.  In other words, the grid impedance of the 
: low mu version is much higher than that of the high-mu version.  For the 
: same class-B driver stage you will need a different turns ratio on the 
: driver transformer.  The 100TH's probably have a step-down driver 
: transformer.  You will likely need a step-up driver xfmr for the TL's.
: 
: The audio driver transformer is the weak link in most conventional 
: transformer-driven class-B audio amplifiers.  It has the most severe service 
: requirements and a good one is complex to build and expensive to 
: manufacture.

In leui of a good, hard-to-find and expensive driver transformer, there
-is- an alternative...

More discussion regarding driving the grids of a class B modulator, the
problems and one person's near perfect solution to the problem, 
can be found at:

http://www.qsl.net/wa5bxo/driver1.html 


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