Paul Ruby Amplifiers

handmade vacuum tube amplifiers
for working musicians
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hi-octane layout

My version of an AX84 High Octane. It's pretty much stock except for the addition of an octal socket for any big bottle tube (6V6, KT66, EL34...). Also note that I reference the filament lines to the power tube cathode for simplicity. This works very well in a HO or P1 and is easier than referencing to ground.

Print the following at 150DPI to get actual size for the turret board.



See a sample build of this layout in my Zebra HO.

Some tips for the best possible build...

The inclusion of hi and lo inputs is somewhat superfluous. To ensure the maximum immunity to noise, consider using a single input jack, shielding the line from the jack to the input tube and reduce the grid stopper resistor to 10K instead of 68K.

Also note the layout follows the golden rule of signal flow. Input at one end, power supply and OT at the other. Have a look at my Zebra HO as an example build. Notice the large amount of white space over on the power supply end.

Similarly, the ground bus is wired in parallel to the B+ rail with the filter caps physically and electrically located with the circuits they feed. As such, this grounding scheme minimizes ground noise, avoids all ground loops and matches the performance of a true star grounding scheme.

In case you don't spot it in the layout picture, note the chassis-circuit ground connection is made physically at the input jacks. There is NO other connection from the chassis to circuit ground. This is critical to avoid ground loops. You can use the jacks themselves to make the connection to the chassis or add a bolt to the chassis with a wire jumping to the jacks or to the ground bus on that end of the turret board. I often just add a wire from the ground bus on the board to the turret board mounting bolt in the upper right corner of the board.


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