Hi - I've also recently found a Duoverb Head and a 4x12. Like new got a unbelievably good deal on it.
The volume thing appears to be perfectly normal.
Loving the sound of the amp - it's fantastic for live work. I wanted a half stack setup, which would cope with venues from small pubs up to larger clubs.
It didn't howver come with the Amp 1 / Amp 2 switch - which i'd really like to find.