On Sunday, October 27, 2019 at 8:55:36 AM UTC-5, Scott Dorsey wrote:
> Bob Simon > wrote:
> >I bought the Jensen ISOMAX years ago because I was told it would eliminate =
> >the cable ground issue. Apparently, it isn't. Do you have any idea why no=
> Maybe you have a different issue. Disconnect the cable. Does the hum stop?
> If so, it's not the cable.
> The isolation transformer should effectively stop any ground loop through the
> cable system. But test it and make sure.
> "Don't guess, measure."
> "C'est un Nagra. C'est suisse, et tres, tres precis."
Thanks! You were right! It had nothing to do with the cable feed. Following your advice to draw all the connections enabled me to identify the root cause.
I had forgotten that there is a high-level connection from the amp's main (speaker) outs to a powered subwoofer which was plugged into a different circuit. When I used a 3-wire extension cord to plug the sub into the power strip for the rest of the system, the hum was reduced to a very low level. Now I have to figure out how to route an extension cord across the room in a way that my wife can tolerate. As an alternative, I wonder if an affordable power isolator exists for this type of issue so I won't need an extension cord (which adds resistance). Are you aware of something suitable?