30 ft rca run too long for a phono to preamp?

I designed a shelf for my table, and emailed it to a local welder, then today while awaiting a reply, I decided to make one myself, just to make sure it would work. It did. I used 2" Mahogany, 4 1/2" stainless screws, glued, clamped and screwed. It's not fine furniture, but it is solid, goes with the equipment stand and room, and best of all it was free as I had all the materials on hand. I can jump up and down right in front of the turntable and it does not skip. My son and I tested it out well.
I tried the Hi-fi news test lp again, and It tracked the torture track with only the slightest distortion from the right channel, best yet. I moved the speakers into the room a bit, and while I don't have my super deep bass right now, I can play as loud as I want without audible feedback distortion. Depending on what the quote from the welder is, I may just keep my version and spend the rest on records. I am now looking to put a slab of granite, Mango wood, or a poured concrete slab ( like a countertop) and probably a sandbox, with the galibier metal inserts into the sand, and I think I'll be done for a week or so.

Thanks for all your help.

Sounds like you're going in the right direction.

The Galibier metal inserts are simply 1" aluminum angle strips purchased at any hardware store, cut to size, and screwed into the underside of the top shelf. Filling the sandbox is a several step process because you need to fill it about a quarter or third at a time, place the shelf on the sand, and whack the shelf with a rubber mallet to compact the sand. Repeat the process until the sandbox is full and the platform is level. This is what I was instructed to do by Thom Mackris.

Mike, is your suspension on the tt working properly or is it getting hung up? I seem to remember the 147 as a sprung mount suspension.

I am using a 15 foot IC between my phono and amp and I don't use a preamp at all. I have used a couple of phonos; Pass, Herron and a couple of home rolled tube units w/o a hint of a problem.

Hello again,

I thought I'd post an update. I replaced the repaired woofers in my speakers and now have the full bass again. I built the wall shelf, placed the table ( I got a vpi scout during this whole process ) on a slab of granite which is sitting on isoballs, moved a couch, spread out the speakers, and I have no problems with footfalls or feedback at any volume level. Life is good.
Thanks for all the help.

Mike