Not being an electronics guy, so I'm going out on a limb here,
Could you feasibly use a MOSFET or opamp to take place of that 3rd gain stage?
It's possible, but personally I would rather put it as the first stage. There is a lot of benefit from having a tube first stage, but personally I think there is more benefit from having a tube final stage, so it would essentially be like putting a solid-state boost in front of a tube amp. Doable, probably wouldn't sound bad, but I think it would take some work to get it to sound the same as the original DW.
And I'm not committing to doing a single-tube DW design, but if I did then Elementary absolutely wins the naming contest.
Welp,
I made the dumbass mistake of leaving my DW plugged in....
Hopefully I didn't cause any potential damage.
Nope, you're fine. I was jamming with a Black Eye straight into an amp right before a 5-day vacation, when it was time to leave I turned off the amp but forgot to unplug the Black Eye, so it was on for 5 days straight. No problems, still runs and sounds great. I think 5 days is probably my record for longest consecutive on time, but there really shouldn't be any problem leaving it on for a week or so, just bear in mind that's going to count against tube life.
Follow up question,
The FMV tone stack is passive, is the Hiwatt tone stack passive as well?
Yessir. Active tonestacks generally refers to putting a filter in the feedback loop of an op-amp; tube stages don't have feedback loops so there's really no (easy) way to do that, so every tonestack in every preamp I make and literally every tube preamp (including full amps) I've ever seen is passive.
So what features/things do you plan to test with this Mini version?
YOU WON'T GET MY SECRETS OUT OF ME, I NEVER LEAK SECRETS.
The DSP chip I'm using for the IR bit has a fair amount of horsepower so it can actually run other effects at the same time as the IR. I'm going to try a few of the ones that are built-in, like compression and LPF/HPF, to see how useful they would be.