Blog Pages


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 . 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....


Modular Recording Console

I am working on a modular recording console. You can follow the design progress on my web page: My page should be back online by the end of this month.

This image is of my first two modules: Mono Fader and Headphone Monitor modules.
The Mono fader module is a single channel fader with one input and left-right outputs. PFL is a separate output jack.

The concept behind this design is to allow the user to interconnect module to module using 1/4" balanced cables.

The dual head phone amplifier HPA-11C is an all discrete design utilizing the 2N5089 / 5087 low noise BJT's. Plenty of drive for modest headphone loads.

At the time of this writing I have cancelled this project and moved on to designing the modules using mostly vacuum tubes.


Noisy By Nature - Analog Synth Show

Took some photos at an analog synth show "Noisy By Nature" in Los Angeles on August 5th 2012.