Hello everyone,

After having built quite a few amplifiers (most class A), I wanted to decide to take on a class AB amplifier. My issue lies with the output stage. I've drawnup a basic design (I'll attach below) that allows for a 4 volt swing across an 8 ohm load for 2 watts of output power. The only issue I've got is the power supply. I need a +10 and -10 supply, and I've only got a 10v 2A wall wart. I've heard of splitting the supply with a divider, but that didn't work for me (the emulated ground's potential kept changing), and the classic 555 negative voltage rail simply couldn't supply the ~400mA of current needed for the 8 ohm load.

TL;DR: does anyone know of a schematic that could produce a -10v, 400mA rail from a +10V, 2A rail?

 

http://www.analog.com/media/en/technical-documentation/data-sheets/7820fc.pdf
LTC7820
Figure 9.

 

At this point, this looks like experimentation - which is fine. How about simply using two 10 V wall warts?

 

The least expensive solution is an inverting switcher, often called "buck-boost" though it neither bucks nor boosts. Switchers aren't ideal for audio because of noise that can fall in the audio spectrum.

 

Instead of making a negative supply voltage, why not make a bridged amplifier that has two amplifier outputs like you show but powered from your +10v supply?
Each amplifier output drives one of the two speaker wires then the voltage swing across the speaker is almost doubled and it will work with your single +10V supply. Since both amplifier outputs are identical then they will each have the same DC voltage at about +5V then an output coupling capacitor to feed the speaker is not needed. Of course one of the amplifiers needs an inverting stage so that the signal swings are opposite.