Mr Lofft,
I just read your ground-loop article in Popular Mechanics, and was
hoping you could help me. Just like the system in the magazine, my sub
(Carver D8) hums and won't turn off, but it does that even when no signal is
input. It is plugged into a 3-prong outlet, and the electrical panel is
grounded. I even tried the sub in another house, and it still hums. Any
suggestions you have are greatly appreciated. Thanks very much for your
time.
--Lanny
------------------------------------
Lanny,
Thanks for your e-mail and I'm pleased that my article on ground loops
appeared in Popular Mechanics magazine--is it in the December issue?
About your Carver subwoofer's hum: Disconnect your coaxial cable from your
AV receiver and/or the speaker cables if you are using speaker level inputs
to the Carver sub. Now turn the sub's power switch OFF and unplug the sub
from the wall, then plug it in again and turn the sub ON. Set the sub's
volume control to where you typically set it (halfway or a bit more. .).
Does the subwoofer still have audible hum?
If it does, then the subwoofer is at fault. You'll need to contact Carver to
see if it's a fault of the sub's internal amplifier, which it likely is.
Let's assume that after reconnecting the sub to the AC wall outlet and
turning it on, the hum is gone. Now connect the coaxial LFE cable from your
AV receiver (or the speaker cables--whichever you are using). If the hum
reappears, then it's a ground loop. Now disconnect the TV-cable or satellite
cable feed to your system at the point it connects to the set-top cable or
sat receiver box. Does the hum disappear? If so, then you need an Axiom
in-line ground isolator:
http://www.axiomaudio.com/groundisolator.html
This works with any TV-cable (digital HDTV as well) set-top box or HDTV but
NOT with satellite tuner boxes. If you use one of those, then you'll need a
ground isolator between your Carver subwoofer and the coaxial cable from
your AV receiver. Check Radio Shack.
Feel free to contact me on my direct line, 1-888-243-3236, 9-5 Eastern Time,
Monday to Friday, or call the Axiom toll-free number any time at
1-866-244-8796 - any of our Audio Experts would be pleased to help.
Kind regards,
Alan
