Re: Valve preamp.
Audio Research developed a range of topologies for RIAA back in the 80's to 90's. These usually had a singe JFET input, then some combination of triodes (sometimes just a single one), a complementary cascode MOSFET stage, then a MOSFET buffer. The RIAA was wrapped around that lot.
They clearly had either power on latch up, or latch up on overload, because there are multiple back to back diodes and zeners, and JFETS configured as diodes (ie D&S connected together) all over the shop.
The schematics can be found on line for anyone remotely interested.
Not suggesting for one minute that this is the way to go, just saying that is what one manufacturer did.
Craig
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