Impedance selector on Nad 3020

[Feanor]

I was just knocking around with the my Nad 3020i today, and was trying to use the impedance selector at the back to change it from 8ohm to 4ohm but found that the switch is locked on, it seems it needs to be unscrewed or something to change it. Any idea on how to do this?

I'm trying to understand the meaning of impedance matching, still trying to figure it out. For example, my mission speakers are at a nominal impedance of 8 ohms, so since the Nad has a 4ohm option, wouldn't this give more power to the speakers?

I'd leave the setting at 8 ohms if you speakers are nominal 8 ohms.

The 4 ohm setting on the amp assumes that the speakers will want more current at a given voltage. I don't know exactly what the switch does on a solid state amp like the 3020i, but perhaps setting it to 4 ohms would limit the maximum voltage. That being the case the amp would deliver less, not more, power to 8 ohms.

However maybe there are other people who know better than me ...