[Amateur-repairs] Fw: [Alinco] Combining speakers

[Ingraham, Andrew]

> Since the newer transceivers are not as simple as a old Motorola =
output
> stage, I would build a passive Mixer and feed a small audio amp the
> results. ...
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> Radio -- <-8ohm side of transformer -- 600-1K side to tied together to
> feed the audio amp. If you wanted to get fancy, you could use a few 1K
> pots to adjust the volume of each input separately.
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> The only thing is I wouldn't recommend tying the transformer =
secondaries directly together.  That would be like tying (shorting) the =
radio outputs together.
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> You could tie one wire of each transformer together and to the amp's =
ground; but I'd recommend a series resistor between the other leg of =
each transformer, and the common mixing point that feeds the new audio =
amp.
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(In the above, "secondary" means the winding opposite the 8 ohm side.  =
Since we're using these transformers "backwards" from how they were =
probably intended to be used, this would normally have been called the =
primary side.)

Ideally you'd want to present an 8 ohm load on each radio output.  If =
you use 8ohm:1K transformers, that means you'd want about 1K somewhere =
on the secondary side, capable of handling whatever audio power that =
radio can feed it (probably well under a watt unless you really crank =
the radio).  If you use 1K resistors from each secondary to the summing =
point, that may be close enough, because the summing point itself looks =
like <<1K (1K/n where you have n radios).

Alternatively, it might be possible to wire the transformer secondaries =
all in series, but this might not work if one of the radios has a =
particularly picky audio output stage.

Andy