What cartridge are you using with your RR2150? MM. MC, HOMC or ? The RR2150 user manual doesn't say what the gain is for the phono preamp when set to MM or MC but that combined with the cartridge's output determine how loud it is compared to other sources. Many separate phono preamps have selectable gain and a variety of loading choices (particularly helpful with certain MM cartridges) that allow fine tuning the preamp to the cartridge to get the best sound possible. Lots of choices for an outboard phono preamp but the first place to start is your current cartridge.