Gain stage, advantages/disadvantages

I've got a Pass x-1 preamp which has a low and high gain option. It's connected to a pass x350 amp. What purpose does the gain stage serve and what are the advantages/disadvantages to either one? I'm sure this is a novice question but I'm fairly new to audio. Thanks!
For someone that is "new" to audio, you've picked the name of a very old and respected audio company for a moniker and purchased some very nice gear. Is this "luck" or are you an old "golden ear" playing dumb ? : )

Honestly though, the low gain stage is probably well suited for line level output that have plenty of signal feeding the source. Since the source is supplying enough signal to start off with, the gain in the preamp is reduced. This "theoretically" lowers the noise floor and keeps the signal purer. At the same time, it also allows the use of greater range on the volume control.

If you run into a source component that doesn't output as much signal or just happen to have a recording that is VERY quiet, you can increase the available amount of amplification ( gain ) of the preamp. As such, Nelson was trying to give you the most versatility with the best sonics that he could. Since he did not know exactly what type of sources you would be hooking up or what their output levels were, he left it up to you, the end user, to decide which path would work best for your specific installation.

If you find yourself having to BARELY adjust the volume control when using the high gain stage, try using the low gain stage. If the situation is reversed i.e. the low gain stage has to be cranked, then switch to the high gain stage. Just make sure that you drop the volume all the way down before making any changes though. Otherwise, you might end up with a BAD situation.

Hope you understood what i was saying and good listening... Sean
>What purpose does the gain stage serve?

It further amplifies the source signal before sending it to the power amp, giving the capability of higher volume. The amplification factor is variably offset by the attenuating action of the volume control to yield the overall desired volume level.

>What are the advantages/disadvantages of either [the low gain setting or the high gain setting]?

In theory, you should set the preamp to employ as little gain and attenuation as you can get away with to achieve your desired overall volume levels, in order to get the most neutral and transparent sound. In other words, if your source already offers enough or nearly enough gain of its own to provide your highest desired volume levels, then there is no sense in having the preamp set to greatly further amplify the source's signal, only to then need to greatly attenuate that extra amplification via the volume control.

In practice, many volume controls are engineered to work best in the roughly 50%-75% area of their ranges. I don't know about the Pass volume control specifically, but you will probably be doing alright if you set the gain control to the position which allows you to keep the volume control around this region while playing most of your sources and software at your personally preferred medium-to-moderately-high listening levels. This will give you enough play on both the plus and minus sides of this range to enable you to dial-in the extra volume or attenuation you might need for particularly quiet or loud material, or to accomodate extra loud or quiet desired overall listening volumes, while best maintaining a generally optimal S/N ratio. (If you have various sources with fairly divergent output strengths, you might find that one gain setting is better for certain of your sources while the other setting is better for the rest.)
Thanks Sean and Zaikesman! Both of you seem to be a rich source of audio information. I'm sure I'll continue to be educated by reading your various posts.