I own a Reference 32 preamp (same as 326, except with power supply in a separate box). I did not do any sort of rigorous testing so I cannot say if any particular setting is the "best." I don't think that the different choices reflect actual differences in the number of gain stages the signal goes through, so the choice of 6db vs. 18db merely reflects the amount of attenuation applied to the signal. With the logic circuit employed by ML to control volume, no matter what one chooses for rough gain setting, volume and balance, the logic circuit switches in the appropriate combination of resistors and minimizes the number or resistors used to achieve the particular chosen level. I would expect there to be minimal differences between choices. If you pick higher gain and then use the lower part of the volume control range you should get the same result as picking lower overall gain and higher volume level settings--for any give volume it will be the same combination of resistors chosen by the logic circuit.
Personally, I would pick an overall gain level that keeps the volume level control in the range where each level change is a .1db step. I also use the preamp's ability to change the gain individually for each input so I can roughly match the volume level from various sources. I use the maximum volume feature to prevent accidents that would result in way too high a volume level being fed to the amps.
This is an amazingly versatile and controllable component--just don't drop that heavy remote on your foot.
Personally, I would pick an overall gain level that keeps the volume level control in the range where each level change is a .1db step. I also use the preamp's ability to change the gain individually for each input so I can roughly match the volume level from various sources. I use the maximum volume feature to prevent accidents that would result in way too high a volume level being fed to the amps.
This is an amazingly versatile and controllable component--just don't drop that heavy remote on your foot.