to help me choose feedback resistor values for my AMP10, I created a spreadsheet (http://www.mediafire.com/?20tdz4xjtoz) that calculates gain, output voltages, headroom etc.
Maybe some of you will find it helpful, too.
It takes as input the resistor values, the transformer voltage and the voltage of your line level signal plus preamp gain if you're using one (if not, just use 0dB as it's gain).
It calculates the rail voltage and the gain, the output voltage and the headroom in each stage.
If you see an error, please tell me.
Since I haven't yet measured the rail voltage of my amp10 dependent on AC voltage the rail voltage is calculated using
VDC = (VAC-1.4V)*sqrt(2)
which assumes a 1.4V voltage drop (2 silicon diodes) over the bridge rectifier.