[Ynze] has built an audio ... the amplifier itself. [Ynze] is using a large toroid transformer to drop his local 230V mains down to +25V and -25V. The amplifier circuit itself is simple ...

[Mikremk] demonstrates this with a simple but effective amplifier using a PCL82 triode-pentode. It’s a conventional tube amplifier circuit in which the triode is a preamplifier for the pentode ...