75 Ohm Cable Upgrade Cleared RFI Noise
 

I live in Weehawken NJ right across the river from NYC and I had been experiencing pretty nasty radio frequency interference on my VPI Scoutmaster set up since we moved here about one year ago. It was noticeable from the seating position once the volume knob was turned up more than 1/4 turn.

I thought it might be my phono pre amp (Moon LP5.3) even though I run XLR cable from it to my JC2 pre amp and XLR rejects noise very well. I was jonsing to upgrade to a "better" phono pre-amp as I was certain this was the cause of the problem.

It wasn't!!

An engineer from the radio station I work at suggested I use 75 ohm solid core wires terminated with RCAs instead of the stranded wire / typical RCA with less insulation - promising that would help.

IT DID! BIG!!!

The clarity is noticeable, especially between tracks as now I don't hear the RFI!!

Next step, connect the ground cable. But I didn't have one, so I decided to pull the stock VPI cable apart a bit and grab the ground wire.

This is what I found (pics below)- very high quality wire, but the stranded nature was introducing a ton of noise. I'm not saying replace the stock cable with an expensive cable, my replacement 75 ohm cables are fairly inexpensive, but boy did the 75 ohm cable improve upon the noise rejection of the stock one! If you are having RFI problems, try this!!

http://i61.photobucket.com/albums/h5...psnqpjgyhh.jpg

Stock RCA cables that came with my Scoutmaster

http://i61.photobucket.com/albums/h5...psxg58p9zi.jpg
http://i61.photobucket.com/albums/h5...pshyyy5p7g.jpg

the ground wire is soldered between the left and right cable - so it does't go all the way through (as I thought it would) from one side to the next.

http://i61.photobucket.com/albums/h5...pss9jwyygx.jpg

http://i61.photobucket.com/albums/h5...psbsxgepgu.jpg


The wires inside the stock cable

http://i61.photobucket.com/albums/h5...psgvvbixnh.jpg

Had to stand the pre amp on its faceplate as the ground wire is fairly small, will get a longer cable tomorrow.

Pio-

Interesting post.
Shielding can act as an antenna and there are many powerful radio stations little more than a few hundred yards away from you, as the crow flies.

The ground wire on your original cables was attached to the shield and then grounded back at the preamp without direct attachment to the VPI's junction box.Did you ever have a problem with hum?

Aside from eliminating the radio interference, have the 75 ohm digital cables made a difference in the tonal quality of your system?

Yep - all the big stations are right across on the Empire State building, including the one I work for, and I have perfect line of sight from my place to the building.

The big sonic difference is clarity, but I think that's just the fact that the RFI is gone, so I was able to turn up the volume a bit more and spent about 3 hours listening last night.

One thing that is also gone is the "thunk" I would get when I would turn the motor off - now there is no thump or need for me to turn the volume down on the pre-amp when switching records out.

Pio-

Grew up in Essex County NJ and know the area well, right by the Lincoln Tunnel.
Now in the mountains, radio stations are few and far between comparatively speaking so in replacing my TT cables I'll stick to something conventional.

Thanks for the reply!