Here is a stripboard layout I did for a preamp/boost using the JAN 6418 subminiature tubes I have been experimenting with lately. It is based on the schematic from the previous post, but rather than powering the heater with a 1.25-volt battery, I utilized an LM317 voltage regulator and a 100-ohm resistor.
This ultra-simple circuit fits nicely on the end of a 19-hole Veroboard. It can be shrunk down to 11×7 and even smaller if you want to cut the Vero.
Take extra special care with pin 3 of the tube; you only want that getting to 1.5 volts max! Hit that with any more power, and you might just be tossing a tube.
UPDATED: There was an error on the previous version of this layout; if you downloaded it or are having problems with your build, please refer to the new image below. Thanks.
Are you looking to get your hands on some of the JAN 6418 tubes for your builds?
Raytheon JAN 6418 pentode vacuum tube – 5 Pack
NOS JAN 6418 Vacuum Tubes
These Joint Army Navy 6418 sub-mini, 5 lead vacuum tubes are perfect for building battery powered boosts, condenser mics, preamplifiers, and even RIAA compliant headphone and phono preamps. This same tube is used in many DIY and commercial products including the Oatley K272 kit and the Audio-Technica AT3060 condenser mic.
Next up will be a phono preamp. It is just a matter of doubling up the tube layout and piggybacking power from one tube to the other. Reviews on these tubes for vinyl are great, and based on how incredible they sound on guitar, I’m sure I won’t be disappointed.