Does Doubling Cube count as the production source of the mana produced by its ability (meaning that counts as mana produced by an artifact) or does it preserve the production source (meaning it is still be mana produced by a creature, basic land, etc.)?
For example, if I have a Llanowar Elves, a Doubling Cube, and three lands, can I double the mana produced by Llanowar Elves to cast Myr Superion?
Doubling cube has a card ruling that it doesn’t copy the any restrictions on the unspent mana, but in this case, the restriction is on the spending of the mana rather than the mana itself.