Vacuum Tube Audio Projects, Part 1: Preamplifiers

You can find more than 90 various audio-related projects on our website and on this channel that are all using semiconductor devices. But this time, we decided to try something different and use vacuum tubes instead.

As a starting point, we will use a low-cost and popular 6J1 tube preamp kit that I found online. The kit does not come with a schematic diagram, but it can be found online with some searching. The kit is suitable for this project because we can replace the original pentode with a superior one, the JAN 5654W.

In Part 1 of the vacuum tube preamp project, we will use a simple and convenient approach. We will use the 6J1 preamp DIY kit as the basis for the first two preamps, but we will not use all the components that come with it.

The Preamp1 project is a simple 2-channel passive Baxandall bass and treble tone control circuit. The tone controls provide the usual boost and cut of the low and high audio frequency spectrum with no effect on the mid frequency. The volume, bass, and treble components are connected together by point-to-point wiring, just like in the old days.

The Preamp 2 project uses an affordable 2-channel passive bass and treble tone control board module, which simplifies the wiring of the project. Some resistors have been modified to improve the tone quality of the preamp. The tube circuit of Preamp 2 is similar to that of Preamp 1, except for these changes.