Here is an example of parametric sweep, showing one possible way of potentiometer and variable resistor simulation in LTSPICE. I will use commonly referenced tone control, originally suggested by James and modified by Baxandall to utilize active tone control scheme.
I scaled values of Baxandall circuit and also used operational amplifier instead of electronic tube used in original schematic. I’m mostly interested in frequency response simulation, so I’m not very concerned with quality of LT1128 model supplied by Linear Technology as “black box”. It should be good enough for our purposes.
Files, used in this example are included in Baxandall Tone Control.zip
You may have noticed low input impedance with some potentiometer settings even with relatively high resistor values. This circuit requires input buffer for most real life application. You should be careful, deciding what will drive this circuit.
Additional bands could be added to provide control over mid frequency range.
While I’m not big fan of this kind of tone controls, and their usability is very questionable to me, we are not going to discuss it now. Purpose of this post was to show one more example of parametric sweep and the way to simulate potentiometer in LTSPICE.