On this site, talk about audio amplifiers:
http://www.angelfire.com/sd/paulkemble/sound5c.html

The following power supply appears:

questions:
- Can I add more capacitor-diode structures to reach a higher output voltage? Keeping only these 2 MOSFETs.
In this schematics an alternating current is used:
https://en.wikipedia.org/wiki/Voltage_multiplier

But we have a rectangular signal created by these two transistors.

I'm waiting for any advice, about how can I get higher output power this way.

Theoretically by increasing the frequency and increasing the capacity of the capacitor.
But in practice, the electrolyte in the capacitor it starts to warm up if a certain frequency is exceeded and decreases its capacity.

 

I take it that you are referring to the lower circuit.

Yes, you can add more stages. Just be aware that you loose two diode drops in each stage and that the more stages you have the higher the output impedance. Keeping the capacitors large (for a low impedance at the input frequency) will help keep the impedance from getting too high.

These things love square waves.

 

You can add two capacitors and two diodes per section to boost each stage, as in a Jacobs Ladder...

 

Yes, each stage will double the voltage but also halve the available output current - much like a transformer.