As of a couple of week ago I’ve been getting the parts together to build my own tube headphone amplifier.  More information on the circuit and construction of the amp will come soon.  For now I just wan to share what I went though to get the box ready for the parts.

The part I’m using is from Antique Electronic Supply and is a 20 gauge steel box (Model number P-H1441-12).  I really can’t describe how unprepared I was to deal with this box.  20 gauge steel is hard metal to work with if you don’t have a garage full of tools and, I don’t have a garage full of tools.  But I’ll get to that later.

Here’s the box on my desk.

The first thing I did was mark the holes for the 3 tubes I’m using, power plug, RCA connectors, power switch and the hole for the cables from the transformer.

I found many websites that said the best way to do this was to use a drill-press.  I don’t have one and don’t know anyone that has one either.  That idea went out the window.  The next thing I tried was to drill a hole and then go at it with a cutting disk on a rotary tool.  This failed miserably.  Two broken disks later and I had barely put a dent on it.  Then I found this tool called a nibbler.  It’s an insanely brilliant tool.  Cuts though this metal like a hot-knife through butter.  It does this a couple millimeters at a time (get it? it nibbles).  I tried to clean up the mess I made with the rotary tool with the nibbler.  It’s the messy hole on the left in the pic.

After some more trial and error I did learn that going counter-clockwise with the nibbler is much easier.  The nibbler has a little tooth on the right side.  It uses this to begin the cut.  When I tried cutting clockwise this tooth didn’t catch and the tool slipped.  Once I figured this all the square holes were a breeze.

The round holes for the tubes weren’t that easy.  It just took a lot of patience with the nibbler and very little bites.  I stopped caring about the jagged edges left by the tool and figured out I could sand them down later.  This turned out to be true, which was a great relief.

This is the finished box with the round holes for the tubes.  The holes aren’t perfect, but this should all be covered up by the bezel that holds the tubes in place.

That was a lot of work.  Now, next step, install everything and wire it up.