Assuming you're talking about your phono preamp, the settings you describe change the capacitive load on the cartridge. Generally this is only an issue for moving magnet cartidges, and the manufacturers usually have a recommended setting. As is always the case, it's okay to experiment and see what settings sound good to you - you won't hurt anything. If you're trying to hit a recommended setting, remember to add in the capacitance of your phono cable; it can be 100pf on it's own.
David
