#1
I have a marshall avt100 but I need it a little bit louder. can i put a cabinet under this combo amp to make it louder?

Peavey 6505+
Les Paul Custom Silverburst

Tool 5/5/06
Tool 11/24/07
Tool 12/8/07
RHCP 4/28/07
RAtM 4/29/07
Black Label Society 3/7/09
Black Label Society 5/4/09
Metallica 12/7/09
Alice in Chains 2/8/10
Lamb of God 7/14/10
#2
i have a valvestate avt 150 and there is an 8 ohm extention jack on the back. If your 100 has that jack then by all means hook it up right through there
#3
Adding a cabinet under an amp rarely makes it "louder." It'll sound bigger, but in terms of decibels, there won't be any difference.
Gig Rig:

Schecter Hellraiser V-1
Crate BV120H
B-52 LS 4x12 cabinet
BBE Rackmount Sonic Max
Boss ME-50 Pedalboard
Digital Reference 2505 Wireless

I don't like BTBAM. Sue Me.

PLUR

My Solo Project