Lowest AC you can get with bard...?

[Crosswind]

just using items, not skills?

What is it, and how?

-Cross

[Obsidian]

Well, if memory serves me right,
you get AC 6 from dex 18
down to -4 with bladesinger chain +5
to - 6 with ring of gaxx
- 9 using amulet of the master harper
-10 with ring of earth control
- 11 with various helmets/stones
-12 with cloak of the sewers
- 14 with 2 prof slots in single weapon style.

So I think that's as low as it can go, attach on Def spin and imp song, and other buffs it can hit -30

[Bruce Lee]

I could never hit -30, it stopped at -26 even in defensive spin and singing the improved bard song.

[MegaToerist]

Create a party consisting of 6 bards, and let the other 5 sing their improved song: an extra -20 to AC. Use simmies to even go deeper.
Using invisibilty and spells that have a negative THAC0 modifier on enemies to even go deeper, you really have an unhittable tank

TC, Geert

[Ode to a Grasshopper]

What about with the Big Metal Unit?
Base AC -10
-14 with 18 Dex
-16 with Ring of Gaxx
-19 with Ring of Protection+3
-20 with Cloak of the Sewers
-21 with Ioun Stones/Helms
-22 with Amulet of the Master Harper
-27 with Sentinel+4 (shield)
-29 with Defender+5 (Drizzt's scimitar)
-30 with Wondrous Gloves

Now add on all the spell bonuses, Improved Bard Song, Defensive Spin etc.

[Obsidian]

Blur gives you a 2 ac bonus, several items that give you that constantly, and imp invis gives you a 4 ac bonus.

[Crosswind]

I don't seem to remember any items that give constant blur...which would these be?

-Cross

[Truedge]

Cloak of displacement.

[Lark]

It seems to be a game limitation that AC is capped at -20 plus AC bonus due to Dex, ending down at -26.
Additionally, you can decrease the opponents chance to hit by using items that grant an AC bonus to a specific type of damage; this is capped at -20.
Less than that is not possible afaik.

Lark