how to use gain control on a preamp


Maybe a silly question, but I just got a Magus preamp, paired it with a Belles 150a SS power amp and find it a bit bright with my speakers. Fellow who sold me the Magus said keep the right and left gain controls wide open. This doesn't work--too harsh in the highs. So I pull back on the gain and it keeps the detail, but where is the optimum?

I feel like I could fiddle back and forth with the 3 controls for quite a while before tame this beast. There are also gain controls on the speakers which has always been a problem figuring out. I try to keep that sort of in the middle (30 yr old Chicago Speakerworks 2-ways). Of course I should put some carpet on the wood floor and drapes up to calm things down too.

Well just wondering if there is some sensible process to follow so I don't wander around in the gain control wilderness.
lynnc
I remember using the Gain and Volume settings on my Audio Research Sp 11 and found that I had the Gain setting at about 75% and used the Volume only after setting Gain..I also remember the older Audio Research Preamp units were supposed to sound better with the Volume at a higher setting,so I moved the Gain control lower to get the Volume control to aprox 12 o'clock high ( normal listening level ) ..Can't really say it makes any difference but I would suggest just set it and forget it....Not sure if that helps but????
If memory serves, I set the left/right gain so that the normal listening range of the volume knob falls in the 10:00 to 2:00 position.
I read an article several years ago that said pre amps were optimized to play with the volume set at 12 noon. this was not regarding signal to noise ratio but another variable regarding circuitry. sorry I do not have specifics
Changing a preamp's gain control often changes its output impedance, distortion spectrum, S/N ratio, and linearity. Each preamp design is different, you really need to experiment with it to find the position that you like best.