[Boatanchors] Speech Amp Again

[Rich Post]

Hi Barrie,

Do you have a junk box 12 volt power transformer capable of an amp or 
two?  Check the no-load voltage with 120 in.  If you find it at 13 or, best 
of all worlds, 14 or 15 volts,  hook it up in reverse to your 8 ohm output 
amp.  It will likely work quite well.  The 15 volts gives a turns ratio of 
8 to 1 which, when squared, gives an impedance ratio of 64 to one.  Fed 
with the amp's 8 ohms out, you will match 512 ohms in the secondary.  With 
14 volts, you will match 587 ohms.

This note will probably start another flame session but "been there - done 
that".  As has already been mentioned, it's not that critical.

73,
Rich KB8TAD

http://oak.cats.ohiou.edu/~postr/bapix/

At 06:12 PM 11/18/2008, Barrie Smith wrote:
>Thanks to the many who responded to my speech amp problems.  there were 
>too many to thank individually.
>
>It appears to me that I could either buy an audio amp with a 70 volt, or 
>600 ohm output, or buy a 8 ohm to 600 ohm matching transformer.
>
>Antique Radio has such a transformer, and I'm leaning in that direction.
>
>I don't know if that's the best way to go, so I'm again seeking advice.
>
>73, Barrie, W7ALW
>_______________________________________________