Hi - I've been searching the internets for information about linux driving a class-d audio amplifier output stage.

Any information I find about a computer driven class-d audio amp, has the computer generating standard analogue audio and a "complete" class-d amp with analogue inputs. However I am wondering if all of those analogue stages can be eliminated and the computer audio driver simply outputs a digital PWM signal to an FET output stage.

Unless I'm mistaken, it would be simpler to have software go straight from an mp3 to PWM and not have all of those interim analogue stages. Does such an audio driver exist?

I can't seem to find any info, so perhaps I'm using poor search terms.

Thanks

I don't pretend to know your exact ambitions here, but IMHO you should probably be looking at a hardware design that can take digital output (eg S/PDIF) and build a class D amplifier that can take that digital input stream and do the necessray PWM conversion (which you should understand is essentially an analogue signal). Are you wanting to design/build your own, or purchase some existing digital amplifier?

You're going to need a soundcard with your desired output. The AMP is hardware, and not part of the computer. There are interfaces with optical outputs and probably whatever output you're needing.

My setup is a RPi 4B 4GB running a pulseaudio over jackdbus with a calf 30 band EQ plugin. The hardware is a usb soundcard (focusrite 2i2) to analog RCA jacks to a NAD amp to minnie maggie speakers. Having a pulse audio server lets me use the good speakers with any of my computers on the network.

Simpler maybe - but how would it sound?

Thanks for the replies. Apologies for the delay as I got ill and then forgot about this ;-)
Yes you're right, a typical desktop type computer would need a soundcard to generate the PWM output. The irony is, this type of soundcard would consist of almost nothing compared to a typical soundcard that has analogue stages and/or conversion to optical etc. But yes, I don't expect desktop manufacturers to change any of that soon.

But your example of the RPI is more along the lines of what I was thinking. Just any one of the digital outputs could go straight into a class D amp (no sound card or a bunch of electronics and conversions between). All it needs is a software sound driver.
You mentioned your setup with a USB sound card and analog RCA jacks etc. Yes, I've setup the same thing as you because I found it to be the most cost effective (some of those hifi add-on boards cost more than the pi itself). I know I should write it myself, but I'm just surprised there isn't already a software driver which goes straight to PWM without needing USB, analogue circuits and a bunch of stuff that isn't needed.

BTW - class D amps these days have specs that rival hifi amps and they're cheap :-)

I grew up with a sanyo mbc-555. On that machine you had to write assembler to toggle the beep speaker/thing to create sound. Basically an ON or OFF setting. Which you did at a certain interval to create any given pitch. No volume control and such. Pissed off brothers and death threats and the likes. Since it was pretty F-ing loud. I was still in Jr. High -ish at the time.

I'm not sure if that's the route you're wanting to take. We have interfaces now. They speak a known language (usb-snd-audio / alsa). With other layers on top of that (jackd / pulseaudio / ...). And various filters (EQ / echo / delay / phasers / and such). My setup basically makes sound an appliance. It's setup on the client machines is as simple as a single file with a one liner. That file is $HOME/.config/pulse/client.conf. It's content is "default-server = 192.168.2.3".