by erichayes » Sun Sep 30, 2007 12:16 pm
It's not only possible, but desirable to hook the NFB to the tap you're using to power your speakers.
I'm gonna make you think a little, John, about what changes would have to be made. (I don't have a schematic in front of me, so I don't know the actual resistance value of the NFB resistor; let's call it 4KΩ.) At a given output level, there will be X volts present at the 16Ω tap. There would be half that voltage present at the 8Ω tap, and a quarter at the 4Ω tap. If the given output voltage is 1 volt at the 16Ω tap and, because this is a canned problem, there's 1mA flowing through the NFB resistor, according to Ohm's law, what would the resistance have to be changed to using the 8Ω tap in order to maintain that 1mA current flow?
Eric in the Jefferson State