# PA amp conversion



## washburned (Oct 13, 2006)

Friend and I are converting an old Grommes-precision PA amp to (I hope) a dumbleish overdrive style. Looking for suggestions for schematic to build to: basic amp is 3 12AX7 gain and master, reverb, Bas/Treble EQ and 6QB5 (EL84) power tubes. 
Suggestions?


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## Wild Bill (May 3, 2006)

washburned said:


> Friend and I are converting an old Grommes-precision PA amp to (I hope) a dumbleish overdrive style. Looking for suggestions for schematic to build to: basic amp is 3 12AX7 gain and master, reverb, Bas/Treble EQ and 6QB5 (EL84) power tubes.
> Suggestions?


Are you guys fairly experienced? If not, this is not a good idea for a first project! You can google around and you'll find lots of bits and pieces of Dumble schematics. If you're experienced, you can pick and choose various pieces and come up with a design for yourself. Some pieces are taken for granted that you already understand, like making up some relay switching to kick the OD in or out. Basically, if you want a complete design that you can just copy you'll be in trouble.

My suspicion is that you guys ARE fairly new at it or you wouldn't be asking such questions! You'd already know the answers! No shame in that, of course. We all start out at the same point.

I'd suggest if you REALLY want to start off with some cool overdrive you go to the "Blue Guitar" site and look for some "TRAINWRECK" schematics, invented by Ken Fisher. They are much simpler than the Dumble stuff yet still very cosmic! Trainwrecks are just as famous as Dumbles in professional circles.


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## washburned (Oct 13, 2006)

*Thanks*

Thanks WB. I wasn't thinking of trying for a dumble clone, just something to get close to the sound......I know enough about electronics to converse, and not put my fingers where they don't belong.....my asociate is an experienced hobbyist having built several modded and from scratch amps of his own designs.......I gave him the old Grommes thinking it would be a good base, but the first version wasn't to my liking so we are looking for a schematic to work from, and a 'wreck could be just the ticket for this amp, except the back end would be a pair of EL84s instead of EL34s or 6V6s.


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