If you have no choice but to hook a "Speaker" output to a "Mic" input,
you NEED to build a simple resistive attenuator, say 10k in series with
the speaker output*, and 100r across the mic input. (Just ballpark
values based on what I've done in the past.
(* Some, speaker outputs, need a low resistance to bias correctly, so
put some 47 ohms across the speaker output too.)
If you can't get enough level, lower the value of the 10k, if it's still
too hot, increase the value.
With care, such things can be built into the interconnecting lead, but
label it so you know what it is for in the future. (Don't ask!)
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