If there are two things people really love, it’s VU meters and Nixie tubes. (evidence here and here). This guy had already figured out a decent circuit for this, but it used a now-obsolete THAT2252 chip for the RMS measurement. The best replacement I could find for this chip was using part of the THAT4301. With a few tweaks and lots of help from THAT app notes and tech support (most helpful tech support I’ve ever encountered, no joke) the replacement was made that supported two outputs for a stereo audio signal. The PCB was fabricated and lots of 0805 components soldered on. Once both 12V power supplies were plugged in the nixie tubes were up and VU metering! Perhaps even more exciting was a first-rev PCB of this complexity working with no prior testing or prototyping, just a lot of datasheets taking up my mental RAM.
I have to admit I thought everyone’s nostalgia for Nixie tubes was a bit silly at first, but seeing these things in action I’m definitely tempted to put these in more projects.
Good things come in threes, and in purple
See it in action: