yo, i'm going to run the 606 thru a digital connector, to get full sound
because there is only 1 level with digital, ' full volume ' , doing this I can discover easier , when a kick or snare is to loud, when bass is to loud,
also when entire mix of my beats is too quiet, So instead of remaking
the quiet beat just set your track slider to like -10 or somewhere, now when
it's recorded in crack your slider up to 0 or anywhere till it's loud enough like the other ones. cool man.

i'm using a tascam digi and 606 with digital I/O , not shure if optical works the same way or if you can change volume on optical

yo i know why this does this now, 0 is unity gain, you don't want to boost it unless nececary emergency rescue of a low recording, so if you cannot record it again at a normaller volume, then you can do upto 8 db boost on it.
it is always better to catch full signals when multi tracking, and then turn them down for mixing, and cut out the 'MUD' , out where they combine.

i still pre produce everything at -16 db, and then Amp the digital signal in the computer, the works good on the 606 too. you cannot even see the wave when recording a 606 beat, then when you boost it, it is way perfect quality, still needs the mud cut usually.