All right, well I just got my Carvin MTS head, and this probably sounds stupid, but; On the back it says "Speaker Output" then has two jacks underneath it, one labeled "1", and the other labeled "2". Underneath the two jacks it says "100 watts". Logically one would plug into speaker output one, but then over a few inches there's another jack; above it it says "Line Out" and below it says "Cabinet Voiced" which it would also make sense to plug into So, not wanting to ruin anything, I came running to UG Could someone help me out?
cabinet voiced line out is for DI recording and/or running straight into a PA
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Oh, all right, so I do just use the first speaker output? And I would guess the second out is if you have two cabs?
Correct. You ALWAYS need something plugged into the first speaker output, the 2nd output and the line out jack are optional.

FWIW, if you ever use two cabs, the jacks are in parallel, so the impedance should be set at half that of the cabs. For example, if you use an 8 ohm cab into each jack, set the impedance switch on the head at 4 ohms.