Impedence Selector Circuit Help

[dpb703]

Reached a roadblock trying to wire the impedance selector switch of the Marshall Clone I'm working on. I have a 4 pole impedance selector switch, and have identified the common with my multimeter. What I don't understand is the wire that goes from the main board to the Yellow (16ohm) wire of the OT. I am using KT66 tubes and prefer to set up the phase inverter as 16/8/4, instead if the 32/16/8 as the schematic shows. If I change the configuration as I want, I would be using the yellow(16ohm)/green(8ohm)/white(4ohm) wires from the OT, would the yellow wire still get the connection to the main board? Can some one explain why the extra connection at the Impedance selector for the yellow wire.
Lastly, I know that I will be wiring my (2) 8 ohm speakers either for 4 ohm or 16, it seems a cop out, but do I really need the switch?

Can't thank you all enuf for the help.

Dan

IMPEDENCE SELECTOR SCHEMATIC.jpg

IMPEDENCE SELECTOR LAYOUT.jpg

[martin manning]

The wire from the 16 ohm tap back to the main board is the negative feedback, so keep that on the 16 ohm OT tap. If all you want is 4 and 16 ohm outputs, you could just use two speaker jacks, one on the 4 ohm and one on the 16 tap, and eliminate the selector. I would use a switching jack for both, and tie the switch contact lugs together so you have a shorted secondary when noting is plugged in.

[dpb703]

Thank you so much for the response. So if I understand correctly, I should be able to to convert the impedance to 16/8/4, so long as I make sure the negative feedback remains connected to the 16 ohm OT line? It does make sense now.

Thank you!

Dan

[sluckey]

The NFB wire to the board will always be connected to the yellow OT wire. When using KT66s you need to change R31 to 100K (see schematic).

[dpb703]

I caught the 100k resistor. Thanks. Ive learned so much this time around.

Dan