Is it possible to bypass the Preamps in a 1680, making it a Line input instead of a Mic input? I know the Digital ins are Line, but I don't have a outboard A/D.
if you can use some sort of outboard pre-amp (or external mixer), you don't have to crank the input pot. that way the effect of the internal pre-amp in minimized.
try to get the input level as hot as you can.
If you keep the input gain pots at zero (full left) that supposedly bypasses the onboard mic preamps. I go into my VS-1824CD through a Mackie 1202VLZ that way. Another, better solution is to by a good quality external AD convertor and come into the VS via the digital input. That only allows two tracks at a time though.