[Alinco] Combining speakers

[Eric Lemmon]

Bob,

The easiest way to accomplish this is to sum the audio with a resistive combiner,
so that none of the receivers "see" less than one speaker load.  This may result
in having to set the individual volume controls much higher than normal.  Be
careful that none of the radios have a DC-coupled (normally a bridged power amp)
speaker output that must not be grounded.  If all radios have single-ended
speaker outputs, you could (for example) feed each radio through a 5-ohm resistor
to the common terminal of an 8-ohm speaker.  Most radio power amplifiers are
pretty forgiving, but if they're not you may have to go to a transformer-coupled
summing bridge that presents a speaker load to each input.  Just be aware that
some audio power amps get unstable when the load is not within a narrow- and
resistive- range.

73, Eric Lemmon WB6FLY

Bob Huson wrote:

> I'm in the middle of rebuilding my operating position and need a little help.
>
> I have five Alinco mobile rigs mounted under a desk bridge. The
> speakers all point up into the bridge distorting the audio fairly
> heavily.
>
> I remember 45 years ago in the news department of the radio station,
> taking the output of Motorola monitor receivers and combining the
> audio for use on a single speaker, but I can't remember just how it
> was done.
>
> It would sure lend to compactness to be able to redo that circuit to
> combine five 8 ohm audio outputs to drive one speaker.
>
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