[font=trebuchet ms]That sounds like an old Marshall cab with that ginky stereo/mono switch. In the stereo setting, the speakers are split into two 8 Ohm pairs. If your amp only has an 8 ohm output setting, you can only run half of the cab with it. If the amp output is adjustable, you are better off to set it to 4 Ohms and run the cab mono 4 Ohms.[/font]