MOTM

>
>I'm in the process of assembling my 410 and am wondering about the
>optional 100k resistor at R68.

Imho, it's a no brainer.  Add the resistor so you can use it with 
other modules.    Without the resistor you still won't be able to use 
it with a guitar or mic without a pre-amp, and the the notion that 
"signals in a studio" are only 1Vp-p doesn't have much basis in 
reality.  I added the resistor to my 410, and it works fine with all 
of my studio gear.