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I acquired an old Bogen Challenger-10 PA amp a few months ago. It's a single-ended 10-watt amp using a 6L6 for the output. Since I read a lot of good things about Trinity's Tramp here on the forum, and the Bogen has transformers and a chassis that are suitable, I decided to give the circuit a try. Because of the size and shape of the chassis, I built the Tramp in a "lunchbox" format.

Here's what the Bogen looked like when I got it.


I gutted the chassis except for the transformers and tube sockets. I repainted the black paint on the chassis except for some of the lettering on the back.

I also repainted its cover using dark bronze paint that dries with a textured "hammered metal" finish.

The Bogen layout for the tubes and transformers didn't allow me to use the Tramp layout, so I had to change a few things. The Bogen was completely wired point-to-point originally.

I wired the power supply and the power amp for the new circuitry point-to-point. But the Tramp preamp is more complex than what the Bogen originally had. It was easier to build this on a turret board rather than wire it point-to-point. There's enough room in the chassis for a small turret board so I made one similar to the preamp section from the Tramp board.


Here's what it looked like when I got everything wired up. Because of the cramped chassis and less than optimal layout, it's not the neatest amp I ever built but it works!

The Bogen originally had a tube rectifier using a EZ81. I left the wiring for it in place but I could only get about 340 volts out it. The Tramp circuit calls for 400 volts for the B+. It also uses solid state diodes which are more efficient than tubes so you get more voltage. Rather than wire in a couple of diodes, I made a little plug-in solid state rectifier to replace the EZ81. I used a couple of tube socket extenders and wired two diodes to the pins inside.


I can easily switch between tube and solid state rectification now, although that doesn't make much difference with a single-ended amp. I didn't implement the Tramp's VRM circuit. If I want to run the amp at lower B+ I can plug in the tube rectifier. It doesn't change the volume much, though.

Incidentally, the Bogen still had all of its original tubes and they all still worked, even the 6L6!

Since I was very happy with the way the project turned out, to finish it off I had a faceplate and a backplate made at a local trophy shop. I drew the layout for them using Inkscape (free graphics software similar to Corel Draw) and the trophy shop used the files to make the brass plates.

Here's the finished amp.





The amp sounds great! I included the Tweed/'Tude and Fat/Thin switches and the Bass and Treble controls so there are lots of tone possibilities. Everything from nice sparkly cleans to dirty and crunchy overdrive. I find the volume control on the guitar quite useful with this amp.

Nice project. How did the trophy shop made the faceplate, is the markings engraved then filled with paint ?

Nice build

looks like a sweet amp

Thanks. It was a fun project.

The faceplates are actually thin aluminum with brass plating and a clear finish on one side. The trophy shop used something they call a "sublimation printer" to do the lettering on the plates. It's very durable. The lettering sort of becomes part of the clear-coat finish. There is no difference in thickness between the parts of the panels that have lettering and those that don't. They can do engraved brass with a paint fill too.

I used Inkscape to do the layout. The trophy shop can use the EPS files Inkscape generates to run their printing and engraving equipment.

Thank you Mitch, I'm looking for options to get a good looking faceplate for another project (a 2x5W Hi-Fi amp with either EL84 or 6V6), and this one is interesting.