Your heat sinks getting hot are the transistors biasing on, thats a problem
See below definition of taper
Resistance–position relationship: "taper"
Size scaled 10k and 100k pots that combine traditional mountings and knob shafts with newer and smaller electrical assemblies. Note the "B" designating a linear taper.
The relationship between slider position and resistance, known as the "taper" or "law", is controlled by the manufacturer. In principle any relationship is possible, but for most purposes linear or logarithmic (aka "audio taper") potentiometers are sufficient.
A letter code may be used to identify which taper is used, but the letter code definitions are not standardized. Newer potentiometers will usually be marked with an 'A' for logarithmic taper or a 'B' for linear taper. Older potentiometers may be marked with an 'A' for linear taper, a 'C' for logarithmic taper or an 'F' for anti-logarithmic taper. The code used also varies between different manufacturers. When a percentage is referenced with a non-linear taper, it relates to the resistance value at the midpoint of the shaft rotation. A 10% log taper would therefore measure 10% of the total resistance at the midpoint of the rotation; i.e. 10% log taper on a 10K ohm potentiometer would yield 1K at the midpoint. The higher the percentage the steeper the log curve
Linear taper potentiometer
A linear taper potentiometer (linear describes the electrical characteristic of the device, not the geometry of the resistive element) has a resistive element of constant cross-section, resulting in a device where the resistance between the contact (wiper) and one end terminal is proportional to the distance between them. Linear taper potentiometers are used when the division ratio of the potentiometer must be proportional to the angle of shaft rotation (or slider position), for example, controls used for adjusting the centering of the display on an analog cathode-ray oscilloscope. Precision potentiometers have an accurate relationship between resistance and slider position.
A logarithmic taper potentiometer has a resistive element that either 'tapers' in from one end to the other, or is made from a material whose resistivity varies from one end to the other. This results in a device where output voltage is a logarithmic function of the slider position.
Most (cheaper) "log" potentiometers are not accurately logarithmic, but use two regions of different resistance (but constant resistivity) to approximate a logarithmic law. The two resistive tracks overlap at approximately 50% of the potentiometer rotation; this gives a stepwise logarithmic taper. A logarithmic potentiometer can also be simulated (not very accurately) with a linear one and an external resistor. True logarithmic potentiometers are significantly more expensive.
Logarithmic taper potentiometers are often used in connection with audio amplifiers as human perception of audio volume is logarithmic.