MuFu 12V Version 2

Here is an the schematic for the next version of my 12V MuFu Amp. You can read about the first version here.

 
RTC-AMP-001%20-%2012v%202-4%20Watt%20MuFu%20-%20Prototype%202%20schematic
 
After thinking about how much current was wasted with the current mirror and  keeping in mind that all the current mirror does is provide a bias voltage for the Q2, I decided to use a voltage divider instead. By using diodes in the voltage divider, the bias voltage remains constant despite any power supply sag or noise. My choice of diodes was based on what I had on hand, and using a single 7-10V zener would no doubt be ok. A zener or diode combination with less than a 7V drop would likely be ok too, I just want plenty of room for adjustment.  A potentiometer further divides the voltage and allows for bias adjustment, which of course adjusts the current through Q2. Just make sure the bias voltage is greater than the cutoff voltage for Q2. The voltage divider uses relatively little current, and the circuit as a whole uses a little more than half the current of the previous version.
 
Another change I made was to replace the 2n7000 MOSFETs with j201's and bias accordingly. This improved the sound quite a bit. With the 2n7000's, there was a definate loss of treble, probably due to the greater input capacitance of the 2n7000's. With the first design, I wasn't sure if this was the speaker's fault or not and thought it could be adjusted via some tone control, but it's better to make small adjustments to something that already sound's pretty good, so I'll stick to the j201's for this design. 
 
I still need to add volume control, and maybe gain control. For flexibility sake, I might leave out the tone control, and just rely on external eq pedals. 
 
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