While with some components doing what you propose might result in a number of issues, after looking at the specs for the PP4, the Ref Phono 2SE, the cartridge, and the McIntosh C2300 preamp listed in your system description (assuming you are still using it, as your line stage), and after doing some related calculations, I don’t see any problems in this case.
One point to keep in mind, though: I wouldn’t be surprised if the RCA output connector of the phono stage for each channel is wired directly to one of the two signal pins on the corresponding XLR connector, with the same output stage providing the signal to both of those destinations. Which means that having the PP4 connected while listening to your system **might** have **slight** adverse effects on the sonics of the system, since it would result in unequal loading of the two signals in the balanced signal pair. But given the 47K input impedance of the line-level inputs of the PP4, I suspect that won’t be a significant issue. Also, though, try to keep the length of the cables to the PP4 fairly short, and/or choose cables having low capacitance per unit length, as the capacitance of those cables (which is proportional to length, as well as being dependent on the capacitance per unit length of the particular cable) can also affect the signals received by the line stage preamp if (as I suspect) the RCA outputs of the phono stage are driven by the same output stages which drive one of the two signals on the XLR connectors.
Regards,
-- Al
One point to keep in mind, though: I wouldn’t be surprised if the RCA output connector of the phono stage for each channel is wired directly to one of the two signal pins on the corresponding XLR connector, with the same output stage providing the signal to both of those destinations. Which means that having the PP4 connected while listening to your system **might** have **slight** adverse effects on the sonics of the system, since it would result in unequal loading of the two signals in the balanced signal pair. But given the 47K input impedance of the line-level inputs of the PP4, I suspect that won’t be a significant issue. Also, though, try to keep the length of the cables to the PP4 fairly short, and/or choose cables having low capacitance per unit length, as the capacitance of those cables (which is proportional to length, as well as being dependent on the capacitance per unit length of the particular cable) can also affect the signals received by the line stage preamp if (as I suspect) the RCA outputs of the phono stage are driven by the same output stages which drive one of the two signals on the XLR connectors.
Regards,
-- Al