Rob, welcome. As Rick(Wid)pointed out, the lower ohm setting on a receiver should never be used. This is a fire safety type of precaution required by UL(Underwriters Laboratories)to help prevent overheating. It does this by reducing the voltage output of the power supply section of the receiver. Following Ohm's Law, when the voltage is reduced, so is the current and power. Lab tests show that the maximum power capacity is cut roughly in half. So, the possibility of overheating is reduced, but at the expense of maximum performance capability. The default 8ohm(or whatever the high setting is designated)setting should never be changed.

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Enjoy the music, not the equipment.