In practical application it helps a great deal to know the load presented by the phono input. I don’t have a way to determine the load presented by the internal phono preamp on the SL-1500C. My guess is that it is optimized for the stock Ortofon 2m Red cartridge. Ortofon specifies a desired range of 150-300 pf for the 2m series. Tonearm/headshell cable aside, can we conclude that the capacitance of the internal preamp is between 118 and 268 pf? Your guess is as good as mine but that seems reasonable.

In the days when Shure (250 pf for the M9x and V15typeVmr, and 400-500 pf for the V15typeIII) and Stanton (275 pf for the 681eee and 881s) cartridges were available, higher specified capacitive loads were common. Even the Ortofon OM series which is about 3 decades old specifies 200-500 pf as a suitable range. Audio Technica was an outlier with 100-200 pf and have remained consistent to this day. Sumiko currently specifies 100-200 pf for the Oyster series. Nagaoka does not list values on their website. Therefore, when combined with the phono input capacitance, the use of the stock Technics connecting cable is likely to bring the load out of range for certain brands.

My guess is that 47 pf at the phono input (Rogue RP-5, Schiit Mani 2) is an exception; values of 100 pf and higher are more common. How, then, can the load be brought into range? Faced with this problem I ordered a Blue Jeans LC-1 cable in a 2 foot length which measures 32 pf (terminated). Therefore, I was able to interface my SL-1500C with my phono input of 100 pf and come up with a total load of approx. 164 pf. This works for the Audio Technica and Sumiko cartridges. The stock Technics cables will likely be suitable for Ortofon. The jury is out on Nagaoka.