"Sudden loss in volume is suspicious. Get a flashlight and magnifying glass and make sure you didn't put one of those transistors in "backwards" - meaning the collector and emitter are reversed. At low voltages, the transistor will survive, but the gain (hFE) will be much lower. Take are really good look at the schematic and make sure you are clear about exactly what solder pad should be the emitter, base, and collector. (It would not be insane to mark them on the circuit board with a pencil or sharpie.) Peterson preamp schematic:
http://www.fenderrhodes.com/org/ch11/fig11-8.jpg"
I switched around the base and collector as per the VV video here
https://www.youtube.com/watch?v=ab7s0HMQpuo , the emitter remains in the same spot.
"On your hum issue, your complex setup may be creating ground loops, high-impedance paths, or simpy have dirty connectors that create high-impedance paths.
Have you isolated the hum down to the preamp itself?
Sort out the hum issue on the least-complex setup as possible. No extra preamp, no effects loop, no external amplifier."
It hums with nothing in the loop (1/4" patch to complete path). It also hums without the preamp 4 pin cable plugged in, I just noticed this but I guess this would point to the PS or power amps, though I don't think it's the amps...here's the thing, the hum is present in the external amp output and in my external cab, which would lead me to conclude that I have a dirty out-of-tolerance power supply, probably needs new filter caps at the very least.
"The distortion problem could be related to an overheating transistor. The outputs in the suitcase bottom would be the primary suspects. I think that also means checking the 1/2Ω resistors (and maybe the 820Ω and 2.7Ω resistors too). You don't get distortion directly out of the Peterson preamp, do you?"
The distortion is present at both the suitcase cabinet and the external cabinet, my guess would be it would have to be coming from the preamp. (I tested with no effects, with and without external cab, and also straight from the harp board which of course, sounds fine)