My experience with the Polytrog thermistor

[Betty Wont]

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.

[lars]

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.