To follow convention you would make the - ground the sleeve, and + to the tip.
I don't know what is going on with your supposed 8 and 16 ohm taps, SS amps have a single "tap" and a minimum load.
Team Trace Elliot #1, Mediocre Bassist #399, Old Basstard #86 Kala U-Bass #22
Swamp Kauri custom 5str. Stagg EUB. Krappy 5er FL.