i just bought a used amp from a guy thru 1 of my friends. it is a Pioneer 400W 4 channel amp. GM-X374. when i hook it up a red light comes on. idk if theres a green light 2 cuz it might b multi colored LEDs. so idl if the amp is in protect mode. the fuses are fine and not blowing.
Welcome! I had a pioneer amp GM something and it had a red light too which i thought was a protect light also but it turns out that red light is the power light. Have you thorougly tried turning up the gains and stuff.