Is it safe

Also it says to NOT DO THAT in the 502P owner's manual on page 8, section 1. Distortion will occur. Really...that's what it says.

Bombaywalla is correct in stating that "the guys here are full of $$$", especially Elizabeth who leaves her gear on all the time, and myself being fabulously wealthy. True, if you're only using one source at a time you're OK...sadly you won't be able to play 2 sources of disparate music at the same time thus robbing you of bewilderingly cacophonous headache inducing events. Otherwise, get a pro audio mixing board and forget about Assumed Diligence.

Al's post is nothing if not succinct, detailed, and absolutely reasonable...you know...now that I think about it, maybe my sister is bipolar.