[Boatanchors] Hii FI amp as speech amp

[J Forster]

Flowertime01 at wmconnect.com wrote:

> Barrie,
>
> Total power transfer from the audio amp to the power amp will
> determine the size of the transformer you need to use.
>
> Audio transformers and 60 hertz transformers are not the same, that
> said a power transformer will work. A 400 hertz transformer will work
> better than 60 hertz. But do not go off and buy one if you do not have
> one.
>
> Spend an hour reading on transformer ratios in a hand book or on line.
>
> You want to reflect back on the value needed to drive the transmitter
> final to the audio amp 8 ohm output (or 16 or 32 or what ever the real
> value of you audio amp is)
>
> So this come out as a turns ratio. Use the input to output voltage.
> 120 volts in 12 volts out = ratio of 10. An 800 ohm load would reflect
> as 80 ohms.
> 120 volts in 6.3 volts out = ratio of 20. An 800 ohm load would
> reflect as 40 ohms.

NO !!!  The formulas for a transformer are:

   Vout / Sec Turns = Vin / Pri Turns
   I out / Pri Turns =  I in / Sec Turns
   Zout = Zin [ Turns Ratio]  [Turns Ratio]

Impedance goes as the Turns Ratio SQUARED !!!


-John
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