RCA Line Out

Sounds like your talking about a hi to low converter. A high to low converter taps onto your speaker wires and converts them to a RCA connection. Now yes that black wire is a ground. On a high to low converter there is no out put for your remote connection. The amp requires that you connect the remote turn on wire to turn it on and off. So if it’s not connected the amp won’t turn on and you won’t get any sound. If you have a stock head unit you will most likely have to tap into a switch ignition source so your amp will turn on and off with the ignition. What kind of car do you have and dose your cigarette lighters power go on and off with the ignition or dose it constantly stay on?

Well I am going to hook it up the the 12volt switched power but I was not sure about the ground wire. When I did not ground it there was no sound from the RCA outputs. So when I ground it there will be sound coming from the stock radio

If you get sound when it's grounded then hook up the groun. Just remember you will not get any sound until you’re able to turn your amp on with the remote wire. You can however temporarily test your setup if you run a wire from the amps + power connection to the amps remote connection. Just be sure to disconnect the wire or your amp or it will stay on and drain the battery. Also if your converter has gain controls don’t forget to set them.

I did that. My amp is on but there was no sound. I am asking that when I ground the black wire there should be sound then right

no it is an 98 s 10. all manual.

Dose it work when you hook up the ground? If not are you sure you have it hooked up correctly? Here is wiring diagram for your truck https://www.the12volt.com/installbay/detail.asp?info=alarm&year=1998&make=Chevrolet&model=S-Series%20Pickup&ID=17462&type=Stereo 

I did not try to ground it yet. I will in just a few and get back to you

it does not work when grounded. Can you help me at all