7591's in a deluxe reverb?

[Jason C]

How feasable would it be to make a Deluxe Reverb style amp (I'm thinking a kit here) into an Ampeg Gemini I with 7591's? I really dig the Gemini's just wish they were in a slightly smaller package.
Jason

[loudthud]

I'm not sure exactly which schematic is the Gemini I. (G-12?) That aside, are the transformers close enough? A little B+ reduction might be required but that's not too hard to do. The biggest pain will be doing a layout and adapting the eyelet board or fabricating a new one. The Ampeg looks like it has more components than a Deluxe so things will have to be packed in there pretty tight. Not impossible, but a substantial amount of work.

[soundmasterg]

7591's can handle more voltage than the stock 6V6 in the Deluxe so I wouldn't worry about the voltages.

Greg

[Dave Curtis, dB AudioTech]

I have some Bogens that use the noval-based version of the 7591s (the 7868), and they normally run over 500V on the plates.

[loudthud]

The 7591 can handle pretty high voltages. Plate voltage is rated at 550V max. Some of the G-12 schematics I looked at had a B+ in the 360V range. Significantly lower than your average Deluxe Reverb. I am concerned that some of the Gemini-I magic might go away with the Deluxe Reverb transformer set. Those tubes will certainly work but might not sound like an Ampeg. Does anyone know the impedance of the Ampeg output transformer?

[soundmasterg]

The 7591 can handle pretty high voltages. Plate voltage is rated at 550V max. Some of the G-12 schematics I looked at had a B+ in the 360V range. Significantly lower than your average Deluxe Reverb. I am concerned that some of the Gemini-I magic might go away with the Deluxe Reverb transformer set. Those tubes will certainly work but might not sound like an Ampeg. Does anyone know the impedance of the Ampeg output transformer?

I see where you're coming from now......Using a DR transformer set puts the voltages up around 420v for B+, which the 7591 can easily handle. There with be more volume, more gain, and more treble with that, especially if the dropping resistors aren't changed in the rest of the amp so that the preamp areas have a higher voltage than the stock Ampeg setup. I'd also want to make sure the DR power transformer could handle the increased current draw that comes with using 7591's instead of 6V6's. It would probably be ok since many people run 6L6GC's with those transformers, but you may have to bias cold to accomplish it, which changes the sound of course.

Greg