What Impedance I use?

"All valve/tube amplifiers have potentially lethal voltages within.
If you are at all unsure of electronic repair, please take your amp to a
qualified amplifier repair technician."

Firstly make sure that the amplifier is not turned on.

NEVER TURN ON YOUR AMPLIFIER WITHOUT A LOAD ON THE OUTPUT!

Firstly you will notice that on the back of your amplifier you will have 3 outputs to "choose from"

One 16 ohm and two 8 ohm outputs.

Now which one do you use?

This all depends on what impendence your cab is.

If your cab is known to be a 16 ohm cabinet, then all you need to do is
connect the head with the cab with a high quality speaker cable.

(NEVER use a guitar cable as it will not be able to handle the high power
that you amplifier is producing and damage to your head, cab and cable could ensue)

If your cab is known to be an 8 ohm cab then you may follow the same procedure
as above, but just insert the cable in to any one of the two 8 ohm outputs.

If you want to connect 2 cabs to your head, you MUST ensure that they are both 16 ohm cabinets,
and then you can connect them both to the two 8 ohm outputs of your head.
(As the two 8 ohm outputs are connected in parallel, thus give out a 16ohm total output to the speakers.)