Since the op-amp output is at or near common potential, the vacuum tube pentode input stage is ... and precise bias setting is not necessary. The schematic shows one channel of a stereo amplifier, and ...

That’s clearly overkill for a headphone amp ... The power supply was put together using some parts I had stripped from an old tube project I was no longer using. The supply design is lifted directly ...

Until the sequel, that is… Let the op-amp do the pinging! Instead of exciting the supply rail impedance with ... currents which are flowing in the power feed, and which could get all over your circuit ...

The pentode is controlled with the pre-amplified signal and acts as a power ... schematic should be all you need to get started. If you want some more background information about tube amps ...

If you’ve ever wondered why something like a radio or a TV could command a hefty fraction of a family’s yearly income back in the day, a likely culprit is the collection of power transformers ...

One of the first tube amps I ever heard was an MC275 ... and there's now a High Speed Sentry Monitor circuit that automatically turns off the power when a worn tube is detected.