Stuffing a 600 Champ with some 5F6 fire, sort of.


Poster Extraordinaire
May 24, 2010
Searched my threads and did not seem to find one with more than a mention of this amp so here goes nothing. I was building this for another cab but had a four foot piece of spruce that I will not be using for a guitar so calculated I could squeeze a slightly diminished in size 600 Champ out of it. A little shorter in all dimensions but I think it should work. An 8" speaker should fit, a chassis that, what! It doesn't fit?


Width a half inch short, aw darn (I did not want to get the height too short). Mind you, the sides are darn thick for a box this size, cut a 1/4" slot on either side and slide the chassis in should work. No power transformer and I might mount the output transformer on the cabinet. Will be using a laptop power supply and then step up the voltage with a high voltage module. Which power tube to use is a dilemma. The 8" I have in mind has a large resonance (how they got some bass out of open back speakers) but it is a 5W speaker.

I have a bunch of 12BK5's that will put out 8W in P-P. Or do I attenuate the signal and go for as much power I can get out of the HV module? I have some 12AB5's which are 6V6's stuffed into a 9 pin bottle for car use, maybe get 15W? That way I can use it as a head and feed some bigger speakers if need be. But it will not be like I do not have other amps to use when more grunt is needed. I have a lot of the 12BK5's, but if I go for the 12AB5 I have one less tube type to hang onto as replacements. I could always reduce the voltage to the 12AB5's if I want them to put out less power. I will probably be flip-flopping back and forth until I start wiring the sockets. Thinking of a 5F5 Bassman type of circuit, a 6AK5 pentode for the front end though, single channel. I have a board I started for a Cathodyne phase inverter amp but will be changing it to a Long Tail Pair. Have some other projects going on so this will be a time filler for when I want to sniff some rosin. The reason for making the cabinet was I was already set up for doing the box joints after cutting the ends for a 2x12 cabinet.


Nov 17, 2006
I’ll be watching this one. I have sone old Webcor iron that wants to power 12AB5s and maybe this’ll get me off my azz.