BAD hum from catv box

Since I live out in the weeds of Wisconsin,I can't pick up
any jazz channels on F.M.
So I got an extra cable box for just the music channels{no tv hooked up].I ran from the analog audio outs to the premp.
with the volume all the way of it hummed really loud,like a really bad ground.If I turned the volume knobs up some,music never got as lound as the hum.Swapped out catv boxes,cables, checked for ground loops etc.with no improvement.I using a Dan Ovando passive pre,to s.s. amp,all
power conditioned,to a pair of K-horns.
Anyone have any idea what's going on?
Well, I'd also conclude that you have a ground loop problem -- which is certainly not unusual with cable boxes. I had this same problem, as has my son. The problem in my system and my son's system were both solved by installing a ground loop isolator, which you can get at Radio Shack for around $20. Try getting a ground loop isolator, and if it doesn't cure your problem you can take it back to Rat Shack for a refund.
Go to Radioshack and pick up a 75ohm to 300ohm adapter and get a 300 0hm to 75 ohm adpater to convert it back to 75 ohm connect them together and but it on your incoming cable.And it will eliminate your hum.
Cost should be less then 10 bucks. This solved my hum problem.
You can always return adapters to radioshack for a refund.