Vintage audio is the best, I’m planning on building a Mullard 5-10 hifi valve amp from the 1950s in the relatively near future as my second valve project (a micro-power valve AM radio transmitter is my current work in progress). The parts are spendy especially the transformers but valve/tube stuff is just so cool and the fact you can just build a 70 year old design using datasheets of the same vintage and have it work just as well now is so refreshing to my programmer brain that’s used to stuff going out of date when you blink. Also I’m a magpie for glass and glowing things.

The downside is of course that the voltages involved tend to be rather unpleasant, the 5-10 design calls for 250 volts off the top of my head and some amps use 500+. Also they’re unspeakably inefficient by modern standards, it’s essentially a statement of ‘I’m putting rule of cool over sensible cost-sensitive engineering and you’re going to love it’ which I’m very here for.