Contact Audio Research as they may have a "resistor kit" to reduce the gain. The ARC LS5 MK III's gain could be changed between the nominal 12db and the higher 18db value with a pack of resistors. These easily replaced the existing ones on the PC board. And the cost was just a few $$ and a half hour of time. I suspect many ARC preamps could be changed this way so give them a call. If such a simple circuit change can be done, and you are not good with a soldering iron, any competent electronic technician should be able to do this for you.
