#1
Ok, all i need is a one post reply (answering the question of course)

Ok, i forgot the relation between head and cab ohms.

was it Head ohm> or = Cab ohm is functionable, or head omhs< or = to Cab oms functionable?
#3
a safe mismatch is running a higher impedance cab than the amp is expecting to see, the amp will push less current. You don't want to run a smaller impedance cab than the head since it could push more current than the amp was designed for, However, some transformers are strong enough to take it without a problem. I would only go one step at the most though.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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