CeaSaR wrote:Yep! Overall circuit current goes from ~355 mA (w/4 diodes) to 10.01 mA (w/3 diodes). I can crank the power output back up by changing the input divider (R9) percentage to less than 75% or push more voltage in (>200 mV). Big difference. Makes it worthwhile from the power consumption and heat generation concerns.
When you do this, please check to see what the DC voltage is at the junction of Q5, Q6, and C3 ... at the + end of C3.
I have a question that has been bugging me about this particular design since I first found it. Why isn't there a larger voltage swing at the output? It shows just a little over +- 3 V. That's a 6 V swing from a 12 V supply. Mayhap you could shed some light on that subject.
OK, it would be more efficient using as much of the available output swing as possible. First, let's give the circuit some capability for higher output swing. This trick is used in most of the older discrete consumer hifi audio amps. R6 supplies current to drive the base (input) of Q3. Trouble is, the higher the output swing, the less voltage across R6, and the less current flows through R6, and less current drive is supplied to the outputs. This is right when R6 needs to supply as much current as possible. So try this:
R6 is 2.2K. Add another 2.2K resistor in series with it. You'll then have two resistors in series where R6 was. Then add a 10uF (or higher) cap with the + end connected to the middle of those two resistors in series. Then connect the - end of the 10uF cap to the wire that leads to + end of C3. That should increase the high drive capability. On another matter, let me know what the DC voltage is at the + end of C3. We want it to be about half the power supply voltage.
[Edit] If the + end of C3 is lower than 6V, add a resistor from Q2 base to ground. Play with the values of this resistor in your simulator and see what value brings the voltage at C3 up to ~6V. Maybe um, 10K to start?
Meanwhile I'll see what the gain should be for increasing the peak-to-peak output.
Pls post a new schematic with all updates. I remember you changed R7.
I don't use simulator software. I use a calculator. I think Bigglez recommended LTSpice.