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We love audio, and we love messing around with it. So when [mircemk] wrote in with his latest audio-mangling device, we had to give it a look. It’s a tube-sound processor implemented in an ESP32 with a WM8960 handling the audio side of things. Tubes are expensive, power hungry, and a general pain in the posterior, so there is incentive to DIY it yourself with DSP. The whole setup is mounted in a Tektronix-inspired case that would be at home on the workbench or in the living room.
See? No tubes!
What’s ironic about the tube sound is that it’s essentially a nonlinear distortion of the audio, but it’s a distortion that can sound better than the undistorted signal. (Take that, engineering!) Push-pull transistor amplifiers tend to distort the top and bottom end of the signal similarly, while tubes round off the tops more than the bottoms. [mircemk] lets you tweak this transfer function, and displays it nicely on the screen.
But there’s one more important way that tubes color the sound — they respond slowly to rapidly changing signals — and [mircemk] says he implemented that as well. We couldn’t find that part of the distortion accounted for in the code, but maybe you can?
Anyway, this is a fantastic audio project, and it just goes to show you how far you can go with some simple parts and clever programming. Indeed, we’ve seen this rig before, with different code that made it a parametric EQ. Once you’ve got the sound turned into numbers, you can math anything at it.
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