very low /no sound coming out of sp

[S H R U G S]

what am i doing wrong? i made sure the volume knob and drive level is turned up(as i sample it via rca cable/computer) and im still getting weak sound out of the 303? the homie told me to turn on ext source when sampling into the 303 but whenever i press ext source then rec , the ext source light goes away? appreciate any feedback . thanks.

[Ill Green]

I believe that if you hit start/end/level, that will boost or reduce the sample's volume using ctrl knob 3.