I recently purchased a SP-404 and whenever I try to record drums over a sample into a pad the sample cuts off while im playing the drums. I dont know how to use pattern select so I just try to record everything into a pad but the sample drops after a couple of drum hits. Ive tried turning the sound down but it still cuts off. Can anyone out there help?

You can only resample 4 voice, this means 2 stereo sample or 4 mono sample. I always try to sample everything in mono in the first place so I don't have to care about stuff like that after.