How Long Cables From Turntable to Preamp?

I think the correct answer will depend on the electrical parameters of the cables and the cartridge used, but in simplest terms the answer is "not very long at all". The signal generator in cartridges is not designed to push a signal very far at all. It might work but there will be degredation. BUT, if you can position a phono stage next to your turntable you should be able to that 6 to 8 feet with no problems.

1.2 meters is the standard tonearm cable length.

As Dan points out, longer can diminish already small cartridge output, and simultaneously increash RFI and hum pickip. So it's the worst of both worlds.

In addition to Dan's very good suggestion of locating the phono preamp near the TT and then not having to worry about the distance to the main preamp, you might want to consider mounting a TT wall shelf (like a Target) right over or next to your rack. IMO, unless you have a very solid rack and a concrete floor, this is the best way to install a TT anyway, and then you could have it close to your other equipment without adding another rack.

If I remember correctly, a few years back I read somewhere or was told by a dealer that once you go over 30 feet with RCA's interconnects then you should go with balanced IC's. I'm guessing you'll be using a decent pair of RCA IC's so as long as your under 30 feet you should be OK. I could be wrong, but this is what I remember. Uriah If you really want a professional answer, make a call to one or a few of the big Interconnect companies like Audioquest, Cardas, or Kimble and see what they think.