sub out to passive or active sub? (1 Viewer)

[Alfonso]

I have an old receiver with a RCA sub out but I don't know if it is intended to be connected to an active or a passive sub. Is there a way I can figure it out, with a multimeter maybe?
What would happen if I connected an active subwoofer to an output made for a passive sub?

Thanks.

 

[John Garcia]

A preamp output cannot be used for a passive sub, period. Preamp outpus REQUIRE that you have external amplification, without which you will get no sound.

There is no such thing as a pre-amp (RCA) output that would be "dedicated" to a passive sub. Passive subs require speaker level (wire) input, as I stated in the previous question of yours.