19 November 2009

DIY Vacuum Tube Prototyping Board

by Bruce Heran USA Flag To email Bruce, type out the email address.

DIY Valve Prototyping Board
This is a project that I made to take care of an ever increasing need to prototype vacuum tube (valve) circuits. As you c
an see from the photos, it really is a test “board”. I do a lot of work with tubes and love to design and improve circuits. In the process I often use various CAD type programs to rough out the designs. I have frequently found that the models do not agree with the final build. Some are right on, but most are off enough to turn a good idea into a waste of time. Thus the need to quickly prototype designs. Now I could have created this board with many additional features - speakers, output transformers, LEDs... But what I needed was a simple way to test single stage tube circuits. So for simplicity I wired the tube pins together (pin 1 to pin 1 and so on). The leads from the pins are brought out to terminals on a “Euro” style terminal strip. I included several other “Euro” strips, a pair of RCA jacks, a 100 k-ohm variable resistor and solderless prototype breadboard. This solderless breadboard is available in various sizes from several sources. If you build one of these boards, feel free to use the idea to adapt it to your needs and use whatever parts you so desire.

DIY Valve Prototyping Board Underside
The hardest part of the build was deciding on the layout of parts. I tried t
o figure out what kinds of parts would be connected to the various tube pins and place the terminal strips in locations where they would make it easy to swap parts in and out of circuits.

DIY Vacuum Tube Prototyping Board
You will certainly notice that there is no power on the board. I have several external variable power supplies and decided they would be fine for prototyping. No need to reinvent the wheel. With a larger board you could easily add power supplies if you desired.

Good listening, Bruce

More DIY Audio Prototyping Tools


  1. Careful using high voltage on the breadboards. They were designed for low voltages and fairly low currents.

  2. Yes, you do need to watch the voltage. You should always check the voltage ratings when selecting parts. Since this is used for voltage gain stages current will be low.

    I have used 300VDC on inexpensive breadboards, but I always make sure everything on the breadboard is spaced out. If you have a large voltage difference in adjacent columns there could be problems. Use a big board and space the parts out.


  3. Hi, Correct. The max I use on this guy is 250. When I need to go higher I will normally build a prototype. Except for power output stages (mine run at about 450-475) all circuitry is at or below 250. Even then some of these boards can't handle that. Good listening, Bruce

  4. Very nicely done. Please keep us updated on this project

  5. Hi, I'm back. I have started to construct a breadboard for the power output stages. This will have high voltages (up to 500). I plan on using stand offs and the actual tube sockets on small turret boards. The leads will go to the Euro style screw terminals. The main reason for the board is like before, prototyping of designs and the ability to rapidly change the parts. I'll post a photo when the board is done. Good listening, Bruce. gofar99@hotmail.com

  6. Yes you all are correct berad boarh are ment for low powered project

    Bun anyway good listening

  7. Hi this looks like an awesome test bed. What wire would you recommend

  8. Back in 2008 a friend and I actually tested the breakdown voltage of such breadboards. We connected 2 variable 400VDC supplies *in series* across various breadboard points, including immediately adjacent rows. We put a small fuse in series with the power, and we ran the voltages up from zero to 800VDC: No problems at all. We were testing a similar concept as yours, for prototyping tube guitar amps.