[Hallicrafters] On Behalf Of Brian Crawford

[Glen Zook]

Believe it or not, a "filament" transformer for either
6.3 or 12.6 volts works pretty well as an audio output
transformer when you have a 500 ohm output.  You hook
the 120 VAC primary to the 500 ohms and the "filament"
winding to the speaker.  The 6.3 volt types work
slightly better for a 3.2 ohm speaker and the 12.6
volt types work slightly better for an 8 ohm speaker. 
But, using either voltage for either speaker impedance
works fine.

Most people have an extra filament transformer or two
around.  If not, they still are available from Radio
Shack in the low current versions at around $7.

Also, you can use a "line" transformer for the 70 volt
public address systems.  Those work fine as well.

Along that line, the old TV power transformers make
pretty good modulation transformers for rigs in the
100 to 200 watt CW output range.  You use the high
voltage secondary (which is center-tapped) to feed the
plates of a push-pull modulator (B+ comes in the
center-tap and the ends connect to the plates) and
then the 120 volt primary in series to the plates (and
screens if the tube is a tetrode or more elements) of
the final amplifier tubes

Glen, K9STH


--- "Michael Melland, W9WIS" <w9wis at charter.net>
wrote:

Well.... the easiest and possibly the best way to
change the output would be to use a 600 Ohm to 4/8 Ohm
audio transformer.

=====
Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco

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