Tempco Resistors

[Aural Research Facilities]

>From: majmoog at leonardo.net (Kevin Lightner)
>
>This may seem dumb, but as I once mentioned awhile back on AH, I have some
>SEM's in an Oberheim 8 voice that do not have Q81's on a couple of VCO's.
>Instead there is a resistor, a thermistor and another resistor.
>One VCO is actually stable with this mod, the other drifts.
>Is it possible to approximate the curve of a tempco by way of other
>thermally sensetive components, like thermistors?
>Are thermistors too inaccurate for this use generally?

Bernie Hutchins mentioned on one issue of the Electronotes Newsletter that
it was entirely possible to use the proper sign (+ or -) Thermistor in place
of a Tempco resistor as long as it had the proper temperature specs (3000 -
4000 ppm/C).  If the Thermistor was off the opposite sign, then that could
be dealt with by the opamps involved.  (Inverting or not).

Ric
The point being, while lots of keyboard types know the value and get price
reports every 15 minutes from the Star Chamber's Synth Pricing Tribunal,
people in the real world still don't know and don't care. - Matt Haines
Aural Research Facilities - http://www.pangea.ca/~rmiller