Long RCA interconnects


I need a pretty long run of RCA interconnects to connect my phono preamp to my integrated. About 18 feet long.  What are some options under $400? 
nitewulf
18’ of single ended interconnects is a recipe for terrible hum and noise problems. 6’ is the practical maximum length for a single ended run. Do you have the option of running balanced cable?
You'll want to make a very short run to your phono preamp, and make the long run from that to your integrated.

As @folkfreak says, balanced is best.
Yes, the phono run is short, but the run to integrated has to be long and since both devices are single ended, it can't be balanced, unfortunately.  I'm hoping a shielded cable will hopefully reject interference.
You might be lucky. I used to have a 30’ run single ended from my preamp to mono blocks. With it running below the floor in the crawl space I used to have no issues. I then moved temporarily to a rental and had to run it on the floor and it was unacceptably noisy so I had to switch to balanced which I’ve been with ever since.  You also want to make sure the output stage of your phono stage is up to driving a long cable (as cable LCR will increase with length) - what stage are you using?