6x9base13 wrote
My knowledge of this stuff is non existent. Since the original post was about pots specifically I hope I'm not derailing this thread,but.....
Whats the limiting factor in getting a pot to perform according to the ideal brown line in that graph ?
Ok, that brown curve is a 10% logarithmic curve I added in just as a reference, since it represents what a perfect Log (Audio taper) taper should look like. If we were looking at a perfect linear taper pot, we'd be looking at a straight line going up at an angle, instead of a log curve.
Now bear in mind that a pot is just a variable resistor. When you turn the shaft of the pot, you can increase or decrease the resistance value of the pot. What is happening inside is that there is a conductive wiper attached to the shaft that moves around a resistive track, normally made of some type of carbon based material. As the wiper moves, the length of this track between its start, and the position of the wiper increases or decreases. This changes the resistance measured between the input and the wiper.
When it comes to taper, this refers to changes in the resistance characteristics of the track itself. A Linear taper track means that the resistance characteristics of the track remain consistant along its entire length. It is possible to vary the rate of change in the resistance characteristics of the track however. This can typically be done in 2 ways: either change the chemical makeup of the track along its length, so perhaps increase or decrease the conductive nature of the track, thereby increasing or decreasing resistance along its path, or the other way is to alter the size of the track surface, since we know that smaller conductive surfaces typically offer more resistance than larger ones.
Based on the above, to obtain a perfect log curve on a pot, the track resistance would need to be altered in a suitable pattern, but with an infinite number of changes to make the transitions between the track areas perfect. However, in practice, probably due to cost more than anything else, manufacturers tend to make log pots by dividing the track up into 3 or 4 sections and using different resistant materials in each section, and this is what gives the stepped nature of the pots you will see on the curves in my graph.
Please note, the above is my layman's interpretation of how these things work, based on what reading I've done. Hope that explains things for you.
