This simple amplifier was published by Mike Rothacher back in 2017 for the Burning Amp Festival
The concept is rather simple. It’s a single mosfet, loaded by a choke, and surrounded only by the parts required to bias it. It is a power buffer with unity gain, it is AC coupled both on the input and at the output, and is meant to be powered by a Meanwell power brick. This makes it very easy and safe to build and use. Or of course you can go as much overboard as you like.
You can read the initial publication text here
The beautiful thing about this circuit is that you can pretty much scale it as much as you want. You can use a wimpy IRF510 to get around 1-2 Watts, you can use the proposed IRFP250 for around 10 watts, or you can go full fearless greedy-boy mode and use a hockey-puck mosfet to reach even up to 100Watts. Provided of course that you have enough cooling to keep the magic smoke inside the mosfet.
In my case, I like using sensitive speakers, so 1-2Watts are pretty much what I love and need. This project will focus on sizing the initial project to work with an IRF510, biased at around 400mA. I will also experiment a bit with different voltages.
An interesting aspect of this design is also how it clips. The choke gives it a nice characteristic that seems to clip the negative earlier and more than the positive. This could be an interesting platform to simulate old-school guitar amps, since it looks like what a “cold cathode” mod would produce. So a subproject will also follow the construction of a guitar amp.
References
M. Rothatcher’s Site: https://passdiy.tv/