• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Mods for RM5

Too many unknowns.

Phono Cartridge model?

Step up transformer model, if there is any (and the capacitance of the cable to it, and capacitance of the cable from it)

Capacitance of tonearm cable plus phono cable all the way to the RM5 input?
Input capacitance of RM5?

Output impedance of the RM5?
Capacitance of the cable from the RM5 output to whatever input load of the next device the RM5 is driving, and the input capacitance of that next device (Resistance and capacitance that the RM5 drives)?

Start there.

This is a system, not just an isolated RM5.

Just my opinions