Blog Pages


Nixie Tube Clock by Dalibor Farný at Tube Depot

The Art of Making Nixie Tubes:

I came across this video while searching for Compactron tubes at Tube Depot.  This is awesome! New production Nixie Tubes!

These modern Nixie tubes are now part of a custom clock called "BLUB KEO" available at Tube Depot.  It looks like Blub Keo began as a KickStarter project at

Click the image above for the Kickstarter video or use the link below.
The kickstarter video link:

BLUB KEO - Color Options

New Production Nixie Tubes 

Nixie Clock - Copper Color

The single digit cycles through the numbers for the hour and minutes. It's pretty cool.


  • Time
  • Date
  • Temperature
  • Alarm
  • Zero Noise
  • Zero Heat
  • USB power connection 
  • Infra red remote
Blub Keo is about the size of a soda can and sells for about $450.00.
For more information see Tube

Thanks for reading,


Gallien-Krueger 400RB Repair with Deoxit Fader Lube

My bass player still owns the same Gallien-Krueger 400RB bass amp he used back when we both lived in Los Angeles in 1989. It had been a while since he had used it last so it didn't work when he powered it on. The power came on, but with no sound at the output.

Everything looked good inside. It was super clean. But, the pots were very hard to turn. I suspected that the old pot grease had hardened and was getting between the wiper contact and the carbon element so I decided to clean all of the pots with Deoxit Fader Lube.

This stuff is amazing. It works so much better than the old can of Shack tuner cleaner I used in the past. A simple spray inside the element and shaft and then rotate back and forth a few times. Repeat the process until they feel new again.

When repairing any electronic equipment make sure to pay attention to what parts will have voltage potentials on them. Notice the two TO3 transistors at the upper right of the next image.

They are part of the power amplifier circuit. One transistor has about +65VDC on it. The other about -65VDC.  Let me tell you that +65V and -65V do not add up to 0V. Across those transistors is about 130VDC of silent killing potential. We must be very careful and respectful when working on electronic equipment.

Thanks for reading,


Universal Audio M610 Tube Preamp

Inside The Universal Audio M610 Vacuum Tube Preamp

The M610 preamp is the same tube preamp used in the LA610,  LA610 MKII and 2-610. The preamp is made up of two separate feedback gain stages that are cascaded one after another.

The UA M610 Circuit

The first feedback gain stage can be adjusted with the "GAIN" switch on the upper left of the front panel. This switch selects a feedback resistor that can add or subtract gain to the circuit. The first tube in the circuit (left tube) is a 12AX7 dual triode.

The following feedback gain stage uses a 6072 (right tube). The 6072 is similar to the 12AT7 dual triode. Notice that the big knob says "LEVEL". This is because it acts like a volume knob and not a gain knob in the circuit.

The first feedback gain stage feeds the 250k ohm "LEVEL" potentiometer and you adjust the input level to the following 6072 feedback gain stage.

More info and measurements coming soon.
Thanks for reading,


12AX7 Vacuum Tube Breadboard Adapters On Ebay


These are now available on Ebay at this link: BB-NOVAL Breadboard Adapters

They also work with other tubes such as 12AU7, 12AT7 and the EF86 Pentode.  You can learn how to design your own 12AU7 gain stage by reading my white paper 12AU7 Gain Stage Example.

Thanks for reading,

12AX7 Vacuum Tube Breadboard Adapter On Ebay


These are now back on Ebay at this link: BBX7 Breadboard Adapter.

Find out how to design your own 12AX7 Gain Stage by reading my white paper "12AX7 GAIN STAGE EXAMPLE on my website at .

If you have any questions you can comment here or contact me via my web page.
Thanks for reading,


How To Build A 12AX7 Gain Stage Part 4 (Measurements)

Part 4 of my video series on How To Build A 12AX7 Gain Stage. This video covers DC measurements, AC gain measurements, and frequency response measurements. SPICE simulation is then compared to the real-world tube circuit.

Thanks for watching,




Two out of the four absorber kits are finally mounted on the wall using the supplied Z-Clips. TIP: You can gain a little more room "absorption" by spreading out your absorbers a bit. This is due to "diffraction", or "bending" of the sound wave. When a sound wave bends around an object, some of the energy is reduced giving an apparent increase in "absorption"


Since these absorbers are fairly large I needed to make sure to anchor them well. Here you see the supplied Z-Clips mounted to the wall spaced 12" apart. Note: they are not perfectly mounted. In fact, not a single piece of my hardware is exact.

Remember, it's more important to get it up and on the wall than it is to worry about having it perfectly mounted. Just make sure it's NOT going to fall off the wall.

Zinc Self Drilling Drywall Anchors

For the right absorber I got lucky and hit wall studs so I just needed long drywall screws for both Z-clips. For the absorber on the left I used zinc self drilling drywall anchors (shown below). You use a drill to drive them right into the drywall. Then you use small screws to mount your Z-Clips. 

I recently ordered (4) DIY422 Panel Kits from Acoustimac in Florida.  These absorbers measure 48" x 24" x 2".  Although I usually order my panels with Owens Corning 703, this time I decided to try something new and ordered the Roxul Rockboard core material.

When I saw the images online I thought I would be building everything except the frame.  However, you can see the image below of how they came right out of the shipping box.  The only thing left to really "DIY" is the fabric covering. Everything else was pre-assembled.

According to Acoustimac, Roxul Rockboard has better absorption properties than Owens Corning 703. I'm not sure I'll be able to detect the difference in my tiny room.

I will be hanging two of these panels from my ceiling as a cloud absorber. The other two will go on the wall.  I will be installing hardware in each corner of the frame to allow me to attached cables from the ceiling. Access to the inside of the panel is the main reason I ordered kits.

I feel Acoustimacs prices are very fair. Each of these 48" x 24" x 2" panels were only $42.00 each including fabric.  I will post more as I finish them.

UPDATE 5-13-2017:
Added simple eye bolts to each corner for hanging.

UPDATE 5-20-2017:
I'm not sure if it helps but I rounded off the frame edges and corners using a belt sander. Image below of an absorber that is going on the wall. (Not the ceiling)

 As the sun goes down I put the fabric on. Make sure to use a good staple gun. I used an Arrow T50 with T50 1/4" staples #504. (Image of a wall mounted absorber)

It's now dark outside as I mount the "Z Clips" that are supplied with the kit. (Wall mounting only) The panels are 24" wide so I mount the clips 6" in from each side and 6" down from the top.

More coming soon: Finishing up the ceiling absorbers and installation.

Thanks for reading,


How To Design A 12AX7 Gain Stage - Part 3

Part 3 of my "How To Build A 12AX7 Gain Stage". This video demonstrates how to build a 12AX7 common cathode gain stage on an electronics breadboard using vacuum tube breadboard adapters.

Thanks for watching,


How To Design A 12AX7 Gain Stage - Part 2

Part 2 in this video series where I show you how to simulate and build a 12AX7 vacuum tube gain stage.

Thanks for watching,


How To Design A 12AX7 Gain Stage - Part 1

Here's part 1 of a 4 part series on building your own 12AX7 gain stage.

Thanks for watching,