@N3VEM@mastodon.radio for audio, you can't beat the dso-138 line for real cheap, or the hantec combo multimeter for a bit more. But those cap out around 100kHz, maybe a bit more. They claim higher but I wouldn't trust them much higher. For radio and digital stuff I got a cheap 90s-era HP with a green CRT, which does actually have a data port if I ever felt the need. you'll pay about as much in shipping, though.