Quad 405-2 AC voltage considerations
I recently checked such a late model Quad. It did not perform well. The power delivery was not on spec. On the outside of the unit there was a marking: 220V. But in real life the unit was wired for 240V. The Quad 405-1 had a selector with 6 positions, in the service documentation of the 405-2, only for four voltages is explained how to connect the wire links to the primary windings of the transformer. In the Netherlands the AC voltage is 230V, this is one of the missing voltages in the documentation, and the other is 130V. Because of the design, the DC power supply voltage of the amplifier is proportional to the AC mains voltage. So 130 V or 110 V does matter! To complete the documentation I drawn the missing link positions. You can also use these diagrams to rewire any Quad 405 and omit the voltage selector with those tiny wires. If you can hear a difference? I can’t tell you, judge for yourself. Before you rewire the amp, check the AC voltage during some weeks, check what is really coming out of the mains socket. Click on the diagram to get a fully detailed version, I also added some colour.