This enhanced Tube Buffer needs higher voltages to work comfortably. Thus it is plus and minus 55V. It is also regulated, using an adapted version of the SuperReg, developed by the Vacuum State Electronics team headed by Allen Wright.source

It is a simple car voltage stabilizer that connected directly to a car battery.The function is to stabilize or filter an AC voltage from the alternator to get a clean DC voltage. A clean DC voltage is required for electronics equipment to operates in optimum condition. The alternator voltage output is regulated and still has [...]

This circuit is used to measure the voltage on a 12V (nominal) lead acid rechargeable battery system. It was specifically designed for use in solar powered systems, but is general enough that it can be used for automotive or other 12V systems. Lead acid batteries normally spend their working lifetime in the voltage range of [...]

This circuit provides an audible and visual low voltage warning for 12V battery powered devices. When the battery voltage is above the set point (typically 11V), the circuit is idle. If the battery voltage should fall below the set point, the LED will light and the speaker will emit a periodic beeping sound to warn [...]

This circuit is used to convert a mono audio signal into a stereo signal that can be panned between the left and right channel by a 0-10V control signal, it is intended for analog synthesizer systems.source