Blog Pages

9/7/12

Vacuum Tube Direct Box

Printed Circuit Boards have arrived. The first Prototype should be built up this coming weekend. I will post photos.

Printed circuit boards have been ordered for my vacuum tube direct box. These D.I.'s will be in extremely limited supply. I only have a small supply of 12U7 tubes and I need to be sure to save some for a few up and coming projects. A total of 5 Vacuum Tube D.I.'s will be built. When they are gone they are gone for good. Stay tuned for installation and testing reports. Gerbers shown below.
Vacuum Tube Direct Box by Trenton Blizzard

The design was built using my vacuum tube bread board adapters. These adapters allow you to prototype tube circuits on a standard electronics bread board. A single low voltage 12U7 dual triode is used in this design. The balanced output is derived from a Jensen D.I. transformer. The circuit on my test bench is shown below.





8/21/12

Vacuum Tube Head Phone Amp


Every now and then you just have to do something that doesn't make a lot of sense.

Vacuum Tube Head Phone Amplifier

After all of the super linear circuits I have been working on lately I wanted to do something that was more about tone than anything else. I had a couple of EL84's and a 12AX7 handy so I jumped in and started building a tube amp for head phone listening.

My vacuum tube bread board adapters made it a snap! This design won't fit into my new modular console format so I will be putting it into a much larger chassis in the near future.

It's made up of a 12AX7 dual triode and a pair of EL84 pentode power tubes. Signal loss from the     EL84 input  to output is about 8db. So I decided to use the 12AX7 to make some gain. You can learn how to build your own 12AX7 gain stage by reading my design paper on my web page www.trentonblizzard.com . I use a Bourns dual conductive plastic pot as a volume control. Input impedance is basically determined by the pot and is around 50k.

I will be adding more detail to this post weekly. Stay tuned....