Playing into an SP-404

[earthjuice]

I have created a Pattern on my SP-404 with drums only.
When I play my synth that is plugged into the Line in via RCA cable with the EXT Source button lit, the button will flicker on and off as I lay down the part, causing the synth part to be choppy. I have turned the gain on the synth down thinking that it might have something to do with the synth volume causing the SP404 to turn off the EXT Source button as some sort of peak protection or something.

Is it not possible to play a live instrument into the SP 404? I have no problems when I am running my laptop and synth while making Samples, only while trying to create Patterns.

Thanks for your help

[I AM]

you probably recorded EXT Source pad in pattern, just go to pattern rec and delete(erase) the EXT Source pad. this is done in rec pattern, when you are in recording(REC is lit) press DEL and then the pad you want to erase, in your case it's EXT Source, then stop recording