Hi Frederick,
The original schematic that Jim posted is not the exact schematic of this PCB board. From my understanding, the schematic that was posted in copper was pulled from the LM4562 datasheet that the CNC is based on.
Since I didn’t design this preamp, I’ll have to guess what the designers intent here was since there are a couple of reasons why one might use a resistor in this location.
The two main explanations that are jumping out to me have to deal with cutoff frequency and leakage.
If we assume that the line preamp after the phono stage has a 100K input impedance, placing ~100K here increases the cutoff frequency to around 3Hz . This can help reduce rumble - very low frequencies that sometimes a tonearm that is “bouncing” around can produce (perhaps because of a warped record). When playing certain records, you may have seen this before when your woofers move in and out very slowly. This uses unwanted power from your amplifier and can compromise SQ.
It also can help with leakage from the capacitor. Capacitors are far from perfect. They have a leakage resistance that creates a voltage divider with the input resistance. Depending on this divider and the DC voltage before the cap, there can actually be DC after the cap. Lowering the input resistance decreases the DC that’s leaking. I’d expect the DC offset to be fairly low even before the cap, so leakage is not a large concern unless an op amp rails out.
Hope this helps