I just thought I'd leave a note about my experience with the Polyphase. The Polytrog is the first version I've built that worked totally correctly. And the only version that included the thermistor as an option. I built the Polytrog without it. I live in Minnesota and we have pretty extreme weather swings as well as home, rehearsal, and gig spot conditions. After a bit I noticed the bias was swinging. As much as 0.5v. Which is enough to deactivate (or over-do) the envelope modulation. I decided to pop a thermistor in there and now its stable to within 0.05v from 50f-100f.
I got the part for a paltry $0.11 from Tayda, and ultimately it was necessary for my build and use conditions. I'm thankful for its inclusion on the pcb.
My experience with an original PolyPhase was that the thermistor was not as critical as the type of op amp used in the LFO. For some reason, EHX decided to use a 1458, and it just doesn't perform well in that particular circuit. Maybe the thermistor was an attempt to get it to work properly in order to use up a mountain of 1458's they had in stock? Who knows. I found a better solution is to use a TL062 in that position. I'm guessing the TL022 would also be a good choice, maybe even works better.
I just know I could never get my PolyPhase to sound/function right, until I swapped that 1458 for a TL062.