Speaker Box

The Speaker Box schematic tells it all. The common points do not connect to earth ground.

I have just been lazy about making the 2nd input dc protection cap switchable. The switch is actually DPDT and I just need to wire it. Never really causes a problem though that I have noticed.

I pretty never use the LINE OUT option, but it is nice to know its there if I ever want to record some sounds direct. If I needed to, I could monitor the output quietly while using the dummy loads without any attenuation. Never really find myself in that situation though.

The speaker connector in the rear is Speakon, and the cable is 4 conductor speaker wire. This goes down to an old silverface Twin Reverb box that has no amp and no grill. Installed are 2x Eminence Delta 12A speakers. They are 12", 8Ω, 400W (800W peak) speakers. Datasheet

The input has both a 1/4" jack and a binding post/banana jack combo that are wired in parallel. This allows me to keep a banana jack patch over to my Bench Box's switchable scope input for easy changeover to viewing the speaker output on the scope.