I thought we discussed this in the other thread. You can measure the output impedance of any stage by loading it high, measuring voltage out, then loading it with lower and lower values until you get half the voltage of when it was loaded high.
With this stage, load it with 100k, measure Vout at 100 Hz across the 100k resistor. You can do any output voltage. Maybe 2Vrms out? If you are measuring with a multimeter, check that the multimeter can read accurately at the selected frequency. Most cheap ones are good at 50 or 60 Hz but not accurate at other frequencies.
Now you are looking for a resistance at which the meter reads 1Vrms across the resistance (if you started with 2Vrms). Start with 1k and measure Vout across the 1k. Keep going lower until it hits 1Vrms. That’s the output impedance.
Please share the value you find for others.
With this stage, load it with 100k, measure Vout at 100 Hz across the 100k resistor. You can do any output voltage. Maybe 2Vrms out? If you are measuring with a multimeter, check that the multimeter can read accurately at the selected frequency. Most cheap ones are good at 50 or 60 Hz but not accurate at other frequencies.
Now you are looking for a resistance at which the meter reads 1Vrms across the resistance (if you started with 2Vrms). Start with 1k and measure Vout across the 1k. Keep going lower until it hits 1Vrms. That’s the output impedance.
Please share the value you find for others.
sim sez around 1K3...... when you use mild values for varying load 
but, truth is ....... loading resistor is practically dominating Rout
so, if you have 330R as loading resistor (mosfet drains to GND), that's it - count on Rout of 330R
but, truth is ....... loading resistor is practically dominating Rout
so, if you have 330R as loading resistor (mosfet drains to GND), that's it - count on Rout of 330R
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