Blog Pages


1176 CLONE

Working on a clone of an 1176 Revision D. Already have the main preamp stage working. Now I need to get the output amp, meter driver and reduction amplifier installed. I will also need to build of the power supply.

However, I will not be using the on board 3-terminal regulator as supplied. I will be keeping the design to the original spec by using all zener diodes. This should be interesting because zener diodes tend to be a bit noisy. We shall see.....


Vacuum Tube D.I. Prototype

Finally found the time to build up the vacuum tube direct box. It is a tight fit but it all fits. I didn't have the actual parts in stock at the time of the build so I used what I had on hand. I will build up a second proto unit with the actual parts soon.

So far I have been powering it with my adjustable bench supply. I will be sourcing a stand-along supply soon. Features are minimal with a single input, a high-z output and a D.I. output. The two knobs are the level controls for each of the vacuum tube gain stages. Depending upon how you set the controls determines if the sound is clean or mean. It can really dirty things up.

An inside view shows the prototype mess. A Jensen transformer sits on the right side. The 12U7 dual triode sits in the middle horizontally. The final version will move things around a bit to make a little more space for the PCB assembly. The pots will most likely be reduced in size on the next rev.


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.


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.