Fisher 500B OPT/Feedback Questions

[tubelab.com]

I knew that I had been there, my daughter was in a cheerleading competition there a few years ago. About those mushrooms, there is a field west of town............

In the sand state world, making smoke is expected. Every once in a while something actually works. The more transistors that you connect together, the more your chances of smoke. Connecting tubes and transistors together and turning the power supply up to 500 volts, created a lot of smoke, but now that I tamed it, it does sound nice.

[Reddy KW]

Originally posted by SY
Reddy, nice SG!

Thanks. It's a '63. I was lucky to find it back when normal people could afford one.

Properly applied to the old Marshall next to it, it sounds like The Lord Has Returned! (carrying a 10 ton chainsaw.)

[wrenchone]

On the advice of folks here, I'll be first trying a feedback amp with the 7591s in pentode mode. Since the Fisher iron I have was designed with that app in mind, it's probably the best fit.

I still want to try using a 6CM7 for the preamp/splitter, with the small triode as the preamp. I'm thinking of using the circuit shown below to feed a classic concertina splitter. Probably too much sand in the circuit for a lot of folks here, but I think that sand and vacuum can be used to complement one another...

Values will follow when I have some time to stare at the tube curves for a while. I'll probably run the input stages using a 250V regulated supply.