What is the middle transformer doing?
And how do I change it to 120V through this?
Thanks in advance.
The center transformer looks like it just exits out through the umbilical cord.
Where does it end up in the amplifier case?
If it is wired for 220 volts now, the mains transformers will have to be re-wired for
110 volt operation.
Who was the original builder?
The center transformer is for the dedicated power supply of the Joshua Tree attenuator.
And no, you don't have to rewire any of the transformers to another voltage. All transformers have dual primaries, and the fuse holder contains a switch that connects the primaries of the transformers in series (for 200V-240V operation) or in parallel (for 100V-120v operation). Simply unclip, flip over, are clip again the fuse holder into the receptacle and you are done.