[R-390] Subject: Re: R-390 Audio Transformer

[2002tii]

Bob wrote:

>The math is great. There is a 'but' in this all.
>
>The audio output on the rear apron/back panel is, (according to
>TM11-856A), is a *whopping* 500 mW.
>
>This also needs to be put into the equation.

No, it doesn't.  No buts, the math says it all.  The "xx volt line" 
system is convenient for sound-sprinkler installers, but otherwise 
(including for our purposes) is simply a more cumbersome way of 
expressing impedance relations between windings ("IF you put 70.7 
volts on this winding, then...").  Dave's magnificent discussion 
shows how to decipher it.  Putting less power (and, thus, less 
voltage) on the "70 volt" line simply means that the power delivered 
to the load is less than the label on the tap you use.  It has no 
effect on the impedance match whatsoever, which is what we care about.

>How much audio is lost by power in the windings?

This also has no bearing on the issue (and, in any case, will be 
insignificant -- matching transformers are very efficient).

>Curiosity makes myself want to know.

Then educate thyself, and quit spreading ignorance.

Best regards,

Don


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