No. There is no dice to roll (or in this case, check to make from the Caster) for determining a DC. It's a set amount that is based upon your statistics. The total DC of a given spell is [10 + (Spell Level) + (Caster's Modifier)]. There is no Charisma Check involved in calculating a Spell DC.
For example, a spell such as Charm Person requires that the caster make an opposed Charisma check against the target that is affected by the spell each round to tell them to do something that they wouldn't normally do. This check is not the Spell's DC, but an opposed roll using only the respective Charisma modifiers. Since the Circlet grants its bonus on all Charisma checks (and this is a Charisma check), you can use this bonus to apply to the opposed roll.
Ultimately, the Circlet of Persuasion does not apply to Spell DCs. However, some spells do require the usage of (opposed) Charisma checks, meaning this still have some helpful value in those spells, just not in the Spell DC area.
The Circlet does not affect spell DCs. Its sole effect is to modify skill checks based on CHA and raw CHA checks.
It affects a few more things than just those two. It affects ALL Charisma based checks(unfortunately, a save DC is not one of them). So concentration checks, skill, ability, attack roles(if you somehow got to use charisma on it), your saving throws(some spells make you use CHA instead of Con for a save) and other check that requires Charisma(a check is a d20 roll which may or may not be modified by another value). =D
An attack roll is an attack roll, not a check. A saving throw is a saving throw, not a check. As far as Concentration checks are concerned, that's probably debatable. I'd say no, though, since that's a check that can occur with or without Charisma, especially since a Concentration check is not exactly a Charisma-based check, it works with Intelligence or Wisdom as well.
Skill and Ability checks work, since those would be noted as Charisma-based.
An attack roll is an attack roll, not a check. A saving throw is a saving throw, not a check. As far as Concentration checks are concerned, that's probably debatable. I'd say no, though, since that's a check that can occur with or without Charisma, especially since a Concentration check is not exactly a Charisma-based check, it works with Intelligence or Wisdom as well.
Skill and Ability checks work, since those would be noted as Charisma-based.
Check: A check is a d20 roll which may or may not be modified by another value. The most common types are attack rolls, ability checks, skill checks, and saving throws.
From the PRD. Also, look at page 11 of your CRB under Common Terms and find Check.
Yeah, but are those Saving Throws and Attack Rolls Charisma-based is the question. Chances are, they aren't. Concentration checks vary depending upon the caster, so whether it can even apply or not (regardless of the modifier used) is questionable.
Yeah, but are those Saving Throws and Attack Rolls Charisma-based is the question. Chances are, they aren't. Concentration checks vary depending upon the caster, so whether it can even apply or not (regardless of the modifier used) is questionable.
That's why I said if they make you use it. An attack roll can be Dex based or Strength based, depending on what stat is used. If, for some reason, I was forced to use Charisma in place of my normal stat, it's a Charisma based check.
As for Concentration checks, they are either Wisdom, Intelligence or Charisma based. For sorcerers, bards, paladins(and I think a couple of others from stuff outside the CRB) have charisma-based Concentration checks.
EDIT: I will agree that concentration checks are a bit iffy on this.
Note that it won't apply to a paladin's saves. Divine grace is a bonus to the save, and the saves are still based on their original ability scores.
However, it will apply to the reflex save of a Lore Oracle, as sidestep secret replaces dex with cha, making the check charisma-based.