A very simple, but useful PCB. A power supply for the Muffsy Relay Input Selector (or anything else that can be powered by 5V DC/1A):
I'd really like a stereo input selector with relays, but those things are hard to find! (Apart from some of dubious quality on the *Bay)
Better make my own then. This one's got a custom footprint for an ESP32 devkit module, but it can also be controlled with a rotary switch.
Here's another project with freely available Eagle project files.
There was a strange little thing that appeared in Danish magazine Ny Elektronik (New Electronics) in 1989. A very simple preamplifier that used two L63 tubes in Class A with no feedback and it operated pretty much badly out of spec. (...
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