The Pentotron


    Using a 6AU6 as the input stage in the Decimator turned out so well, I thought I'd try it again! I picked up a bunch more 6AU6s real cheap (from a fellow Ampager), and soon after that I was trying to figure out whether an amp built only with 6AU6s would work.

    I had to learn a lot more about load lines and all those other things that go into designing an output stage (schematics for self-split 6AU6 power amps are hard to come by!), but that was also part of the idea. I think I'm going to have to go through several more designs before I can honestly say I know what I'm doing, though…

    In terms of construction, the Pentotron is a cross between the Tonerator & the Decimator. A simple U chassis with ears for screwing it on to the case, and a plexiglass front panel that lets you see the tubes. This time I was lazy and just screwed the box together, but it's not exactly so heavy that it needs to be real strong. The wood is 6 x 1/2 poplar with a light oak stain.

    The cool pentagonal knobs were made for me by my friend & co-worker, David Wegmuller . He makes lots of brass model train stuff from scratch, and accepted the challenge of making the knobs for this project. Thanks, David!

    I've still got one more "upgrade" planned: a new plexiglass panel with the Harmonic Appliances logo and control labels etched into the back.

    The Pentotron is a nice little practice amp as-is (especially if you like a "dirty" tone), but I'll probably keep experimenting with it for quite a while, too.


These samples were recorded using my '73 Telecaster with Barden pickups. As usual, the microphones were a Shure SM58 and an AKG C1000S (one on each channel). The Pentotron is pushing my Weber C15Q speaker.

      Blues lick [179KB]       gain = 1/2; neck pickup

      Different World (lead) [196KB]       gain = max; both pickups


Copyright © 2002 Mark Lavelle. All rights reserved.