How Long Cables From Turntable to Preamp?

the first responses are the correct (and practical) recommendations, but since I had a similar issue last year I did some experimentation. I ran a 2 meter RCA connected in line with my phono cable using F/F rca adapters (which has to be the worst way to do this). This gave me a 3 meter length to the phono input on my preamp's inboard phono section. I was pretty content with it, but didn't do any really critical listening at the time, nor was I using a top line table/cartridge with this setup. It was a perfectly acceptable setup IMO, though if you listened carefully there was a little more noise. I was still pleased with my vinyl.

I also ran a similar setup but using an outboard phono preamp, with a 3 meter ic from the phono to the linestage preamp. Except for some special grounding I had to install, the result on this was better, and probably will stand up to more critical listening.

net/net - I suggest you try it out and see how satisfied you are with your own setup. I doubt you have anything to lose but the time it takes you to set it up. I certainly think you'll be more satisfied with the sound of a phono with 3M ic's than no phono at all.

I'll grant this one exception, which is: if you're using a high output moving coil cartridge (that means 2+ mV as opposed to 0.2 -- 0.6 mV), you could probably go six to eight feet without much problem.

MM cartridges, although they also have higher output, are susceptible to cable capacitance build-up over much more than 4 or 5 feet, so even though they have sufficient output voltage to drive a longer cable without noise, you will start to get non-linear frequency response problems unless you add capacitors to compensate.

Why not use a passive or battery phono step-up transformer?

OK, let me see if I understand this.
If I use, say 9'-10' of cable from my pre-amp to the phono stage... and the phono stage is right adjacent to the turntable... I should be OK?

Yes, you have it! Your phono stage is going to bring the signal up closer to what you would get from a CDP and will be much less susceptible to cable resistance and capacitance. Single ended will be fine. All things considered it is the easiest method short of the wall mount that Nsgarch suggested.