ATTiny85 70 watt amplifier?

Anyway, at the moment I use a class A amplifier which uses a TIP31, it sounds perfectly fine, but I'm wondering how on earth this guy did this.

If you’re looking for a DIY amplifier project made with a minimum of parts, this is the build for you. [Rouslan] created a 70 watt class D amplifier using an ATtiny45 and just a few dollars worth of additional components.

A class D amplifier simply switches transistors of MOSFETs on and off very rapidly. By passing the signal produced by these MOSFETs through a low pass filter and connecting a speaker, a class D amp is able to amplify a signal very efficiently. Usually, these sort of amp builds use somewhat esoteric components, but [Rouslan] figured out how to use a simple ATtiny microcontroller to drive a set of MOSFETs.

The programming side is a little scary, but what's the general principal (the theory) of how this works?....

Class A amplifiers rely on keeping your transistors in the linear region. Class D amplifiers use PWM and just slam the output transistors open and closed. Much easier to do with digital electronics. :)

And it's very efficient compared to class A amps. Add to that the fact that the MOSFETs are operated as switches(that's where the efficiency comes from) you don't have the heat and big heat sinks required with linear/Class A or class B amps.

Designing & building a 70W watt amp is not that easy… You are probably going to fry a few components and maybe even fry a speaker. About a million years ago, I built a preamp. Before the design was finalized & debugged, it oscillated at an RF frequency (which of course I couldn’t hear), and it fried my 120W power amp!

Building an amp with an Arduino is probably a great way to learn about class D amplifiers, but I’d start with lower wattage… And If you want to build a good-sounding, reliable 70 W (or more) amp, you are better off using an amplifier chip and the chip-manufacture’s recommended design.

It’s virtually impossible to build a 70W class A amp, although some crazy audiophile may have done it. :smiley: The most common design is class A/B, where there are separate transistors (or MOSFETs) for the positive & negative half-cycles (the class B part), and a small bias current (the class A part) and usually negative feedback, so that you don’t get a “glitch” when the AC signal transistions between positive & negative.

Been there done most of that. It’s just an interesting project. Rarely do I need 70W RMS. I just think it’d be something to play with.