Building a low wattage JCM800

[peckjed]

Hey all, Im looking to build a low powered JCM800 based on this: https://robrobinette.com/RR2104_Master_ ... JCM800_6V6

I have the transformers listed below laying around and was wondering if it would make sense to use them in this build. I understand my output transformer doesn’t have a center tap but I figure I could create an artificial center tap Any thoughts?

Mercury Magnetics FM45-PLB Power Transformer - Universal dual primary — 270-0-270 unloaded B+ — 70V bias winding — 7 amp center tap. — 6.3V filament winding — 4A-5V winding — 8087 size. https://www.mercurymagnetics.com/product/fm45-plb-2/

Mercury Magnetics SE-3K Output Transformer - Single ended — 3k primary — 4, 8 & 16Ω taps https://www.mercurymagnetics.com/product/se-3k-2/

[xtian]

I have never heard of using an SE OT for a PP build. Don’t think it can be done.

[peckjed]

What about the power transformer? Just trying to not spend any extra cash if I’ve got some parts laying around!

[xtian]

Sure, that PT is up to the job.

[martin manning]

Using that PT, the plate voltage will be around 30V low as compared to the schematic. Since MM does not provide any current rating, that is an unknown, but you’d think with a 7A filament winding it will handle a couple of 6V6’s. The OT is definitely out.

[xtian]

Yes, the B+ will be lower, as Martin points out. To me, that's a plus. The volume wars are over! Focus on tone. I like 300-350v on 6v6 plates.

[didit]

Hello -

With 270VAC along with 7A for filament and 4A of rectifier voltage that transformer was designed for different beast than RobRob's micro. More like a low voltage low power twin or similar. Perhaps you can sell it, and then use proceeds toward getting recommended Allen iron (as a 2nd recommendation). Aaron correctly notes that output power wars are over, however getting preamp plate voltages at correct operating points is helpful in achieving "high-gain" tone. Tweaking B+ can be an exercise in frustrations.

Best .. Ian