I suspect the input capacitance of the GCPH plus your phono cables is too high for that cartridge, but that is just a guess. Its not published, but PS told me the input capacitance for the MM/47K input is 100 pF. I have an AT 150 MLX that requires a max of 150-200 pF, and is reported to sound bright and edgy with higher capacitance. 150 pF is reported to be the optimum, but with the GCPH 47K input of 100 pF and an arm wiring capacitance of 30 pF, it leaves only 20 pF for the cables. Almost impossible to obtain (unless you want to pay thousands for the interconnects).
The Mac may sound better because it has a much lower input capacitance at 65 pF.
In my case (see my post under analog on the AT 150) I solved my problem but using a 5:1 attenuator ahead of the MM input on the GCPH. This isolates the 100 pF input cap from the cartridge, and now I can use 100-120 pF cables without exceeding the 150 pF loading on the cartridge.
I use a gain setting on the GCPH of 60 dB to compensate for the attenuator.
The attenuator is easy to build. Its located in an inline RCA adapter that plugs into the GCPH inputs.
The Mac may sound better because it has a much lower input capacitance at 65 pF.
In my case (see my post under analog on the AT 150) I solved my problem but using a 5:1 attenuator ahead of the MM input on the GCPH. This isolates the 100 pF input cap from the cartridge, and now I can use 100-120 pF cables without exceeding the 150 pF loading on the cartridge.
I use a gain setting on the GCPH of 60 dB to compensate for the attenuator.
The attenuator is easy to build. Its located in an inline RCA adapter that plugs into the GCPH inputs.