15 foot RCA cables out of TT with no pre amp?

The effect of cable length is as a multiplier of the capacitance per foot of the cable. A typical MM cart has an ideal capacitive load for flattest response. You have to know the capacitance of the internal wiring of your EVO, subtract that from the target, and divide the result by15 to know what type if cable to use. Getting this info ain’t always easy. The recommendation of BJC LC-1 with an added ground wire seems pretty sound to me. 

I failed to mention the Onkyo receiver preamp has its own capacitance. If the EVO has 80 pF and the preamp another 80 pF you need a IC with next to zero capacitance...as the target is 200 pF for Ortofon 2M. Hence the recommendations for a closer placement using an outboard phono stage. 

If you didn't encounter noise/hum problem with 15 ft cable, increase the high by using the tone control on the Onkyo stereo to compensate the high frequency loss.

HUM CITY

I am surprised no one else mentioned this, but not more than a few weeks ago, another guy asked about using a 22-foot phono cable.  You might search for that thread; all of the responses also apply to yours. Or was that you?