Thanks to both Al and Mofimadness, really appreciate the response and will stick with 47k ohms. Incidently the Grace F9Ruby seems to mate very well with the Herbies Most Excellent mat
MM Phono Input impedance change 47k to 100k ohms
The well-written AudiogoNer Raul states that the Grace F9 Ruby MM cartridge is best matched with an input impedance of 100k ohms vs the standard 47k ohms. May be a dumb question, but is this a simple resistor swap that I might be able to handle or should I best take the preamp to a technician?