I have a 5150 and an oversized Mesa cab. The cab is loaded with vintage 30s. I'm stumped on the ohms of this cab. Before I plug a head in, I'm needing to find out what ohmage it is. It has 4 input jacks on the back of the cab, with the following labels: 4 ohms-split for stereo/4 ohms bi-amp/8 ohms out/8 ohms in. The person who sold me the cab said it was a 16 ohm cab, and had the Mesa Dual rec plugged into the 4 ohm-split for stereo jack. The amp is fucked, but I got a REAL GOOD DEAL on the amp/cab. The amp makes a crackling sound, so it's going to the shop. I am reluctant to plug in my 5150, until I find out what ohm rating to switch to. Also, if I plug in the 5150 for drty, and the dual rec to switch to clean into the Mesa cab, what ohmage should I set both heads too.