hooking up an old speakers with built-in amplifier with my new Samsung sound bar since I want to use my sound bar for karaoke but it has no port for microphones
You need to connect your old speakers & amp direct to the TV audio out, not the sound bar as that's designed to be hooked up to a sound source (the TV in your case), your speakers & amp are not a sound source.
You need to connect your old speakers & amp direct to the TV audio out, not the sound bar as that's designed to be hooked up to a sound source (the TV in your case), your speakers & amp are not a sound source.