Well there are only a couple of choices on this one... either this is the way it is (the preamp output being quite high for example) or there is something funny with these 'ere pots you have. Like them not being a log taper. There is nothing else it can be.
Sounds like you have few pots there... there is an easy two minute experiment to see if we can determine whether these pots are OK.
All you need is a 9 volt battery like a PP3 and a few bits of wire and your meter set to measure volts DC.
As you look at the front of a pot looking "into" the spindle, orientate it so the terminals are at the top. Now there are two gangs (each identical, one gang is the front row of terminals and the other gang is the back row) so using either one (front row or back row, it doesn't matter which) connect the battery negative to the RIGHT hand terminal. Connect the battery positive to the LEFT hand terminal. Now connect your meter to read DC volts between the battery negative and the middle terminal of the pot. It's easiest to solder all the wires rather than trying to hold it all
Doing that puts 9 volts across the pot end to end.
As the pot is now rotated from minimum to maximum the DC voltage will vary from 0 to 9 volts. If it's a linear pot it will vary in equal amounts with angle of rotation. Quarter of the way around and you get 2.25 volts, half way round and it's 4.5 and so on.
If it's a log pot you will find you have to turn it a lot from minimum to get a small output and then the output progressively gets larger with ever smaller angle of rotation. Look at the Figure 4 in the "Westhost" link I gave above to see if the output seems to follow a log curve. Do you see... at half rotation (the midpoint) you should only be getting around 20% of the 9 volts. Make sure you aren't getting something like the "anti-log" curve.
If you think it is "the way it is" and that perhaps modern high output sources such as CD are a contributing factor then it might be possible to attenuate individual inputs by a resistor change.
Only point to watch doing this is not to allow the wiper (middle leg) to accidently short to either end pin. If that happened then at either min or max rotation all the battery current would flow into the ever decreasing resistance and burn the pot out. Best to solder the wires for a test and to run wires to the DVM too so it's all physically stable.