One other thought.
During a discussion yesterday on this group, measurments were taken as to what the OUTPUT levels were from Ch0.
They were 200mv peak to peak IIRC.
As such, I think I'd want to assume that this would be the maximum level that any of the ports could handle and would want
to account for.
0.6v (600mv) for a basic diode to start clamping sounds a bit risky to me.
If I'm missing something here then I'm willing to learn ;-)
73 de Andy