Normally, vacuum tubes rely on a resistive heater to eject ... [J.G.] is powering this amplifier with a battery outputting 5V via a USB connection, and driving a fairly standard set of speakers ...

Making vacuum tubes with all the proper equipment — glassblower’s lathe, various kinds of oxy-fuel torches, all the right hand tools — is hard enough. But when your lathe is a cordless drill ...