Is this potentiometer linear or logarithmic?
The confusion is because some manufacturers use A for 'log' and B for 'linear', while others use A for 'linear' and B (or C or L) for 'log'. 

You can easily tell the 'taper' type with an ohmmeter. Just rotate the knob to half way and measure from the wiper to each end. A 'linear' pot will read approximately the same on both halves, while a 'log' pot will read about 10 times higher on one side than the other. As usual it is best to do this with the pot disconnected from the circuit, to eliminate possible interference from other components.  

Potentiometer Tapers