It's better to use shorting plugs on your unused inputs. That way you keep the jacks clean AND you ground the center pin of the jack. What does that accomplish? Two things:
A.) It's then impossible for the jack to pick up RFI in the first place, and
B.) You won't hear a 'pop' as you rotate the source selector through the unused input(s) as sometimes occurs with certain preamps.
On unused outputs, you could use Cardas Caps, but caps on outputs don't have to be metal and are just for protection, it's much cheaper to cover them with those cute little red or black vinyl caps ;-)
A.) It's then impossible for the jack to pick up RFI in the first place, and
B.) You won't hear a 'pop' as you rotate the source selector through the unused input(s) as sometimes occurs with certain preamps.
On unused outputs, you could use Cardas Caps, but caps on outputs don't have to be metal and are just for protection, it's much cheaper to cover them with those cute little red or black vinyl caps ;-)