The hummmmmmmm is GONE!

[david (d.a.) gallagher]

Greetings,

This is a follow up to a previous post wherein I was seeking advice on
eliminating a hum that occured in my system after a recent system
upgrade. First permit me to publicly thank the many of you who
responded to me with information as well as suggestions on trying to
resolve my hum demon.

First, to recap my situation: I recently replaced my Luxman receiver
with a Marantz AV-600 pre-amp and a Parasound HCA-1206 amp. This
system also does double duty in a home theater setup. The Parasound
amp utilizes a grounded, 3-prong, AC line, whereas my Luxman didn't
(standard 2-prong polarized plug). With a couple of phone calls to the
people at Luxman and Parasound, I localized the source of the hum to
my cable TV coax feed. Thus my journey into ground-loop territory
(hell, for a while).

I had a few replyers who helped me understand the potential
sources/causes of ground-loop hum. It was suggested that I try a
cheater plug: this worked 100% by also reversing the polarity as well
as eliminating the ground connection. As a number of you have seen the
discussion on this topic, this made me nervous not having my amp
grounded to the AC system as designed. As suggested, I called the
cable company out, and demonstrated the hum problem. The technician
tried a number of house connection changes (direct connect to TV
cable; eliminating the ground connection; wiring a new ground
connection; different connectors, ...). Nothing worked, and he/the
cable company did nothing further.

Also suggested was to ground the outside (ground portion) of the
incoming cable TV coax lead to the AC ground of the wall outlet. That
reduced the hum by about 50%. I tried running thru a Panamax Coax-Max
6 AC and cable surge/filter box, and that achieved 80% reduction. I
also tried a couple of home-made filters: 1) 2 F-conectors with .01mF
cap between the ground leads -> no effect, and 2) the .01mF cap
inserted on the positive lead and the negative sides connected -> no
effect, and 3) the .01mF cap on the positive lead and the
negative/gound sides NOT connected -> 99% reduction, but also a small
reduction in perceived picture quality. Hey, it was fun smelling the
fumes from a soldering iron again! (BTW, just to feel like I'm
high-end, I bought 5% silver content solder!!) I then ordered a small
device from Luxman that is labled as a ground loop eliminator. This
cost about $15 (alot less than some other sources I was quoted), and
worked 100%. It has a coax F-connector input, and a RCA wire output,
upon which I had to add a RCA to F-connector converter terminal (not a
very clean solution.) However, I noticed a small degradation in the
picture quality (a bit more graininess, image edge blur). And since my
cable sucks (IMHO, and please excuse my soap box stand), I was still
unhappy/frustrated.

Then, just when I thought nothing will work (except for maybe one of
those big buck boxes), I saw at my local Best Buys store this single
little device which was coax in and out and was labled Noise
Eliminator. It was opened as a return, but I decided to try it as a
"what the hell". It is a small black tube with a F-connector input
with a short coax cable output with a F-connection. It worked 100%,
AND to 2 other people the picture seemed as good, or one said its even
better with it on!!

So, I'm happy with it. It only cost $11. It is made by Woods
Industries. I believe the part number is 7031. Their phone number is
800-447-4364. Many thanx again to the members of this newsgroup for
their generous responses. Perhaps with this information/post I can
help others out there with similar situations/setups.

Cheers,
David Gallagher
david.g...@nortel.ca