Nakamichi Pa-7 Nakamichi CA-5 Noise Problem Input

I have a Nakamichi PA-7 with a Nakamichi CA-5 pre amp. I have had it since new and have never been able to input anything TV related through the pre amp without a very prominent line noise - the kind that lets you know you're doing something that you're not supposed to.
Does anyone know why I can't input, for example, my Cox digital music channels through my system?
I'm not able to respond to the Cox Digital source but can in regard to a normal TV audio feed. My Nakamichi CA-1 (as well as all my former pre-amps) had severe signal noise with any source that had it's own amplification. I discovered that if I opened up the TV volume to maximum (while turning off the internal TV speakers) the line noise disappeared. So, I assume the problem existed in the poor quality electronics in the volume pot. Good luck!
I too had a similar problem. I floated the ground on the amp
(cheater plug) and the problem diminished. I also took two 75 to 300ohm transformers and connect to 300ohm sections together. that'll give you two 75 ohm f connectors to patch into your cable feed. This solved my problem. BTW this is a poor mans Magic Box & it works just as well & saves you $90.
Hope this helps.

You may be having a ground-loop caused by your cable. You can get an isolation transformer for it for a few bucks ($5 or $10) that will isolate the cable ground from the system but let the signal get through. Your tv service man can let in on the details.
My first thought is the Nakamichi pre-amp and amp in question are analog units. I don't think they accept a "coax" digital signal.

Also I don't think feeding them anything but a "Line Source Signal will work. Meaning no amplification of the signal before it enters the Naks.

Hope this helps.

I sold my old Nak CA7A to my bro in law and hooked it up for him in his system with a dvd and cable being fed into the preamp's inputs which are all connected to the TV as well. At first, I used a Mapleshade powercord feeding the Nak, and there is a nasty hum as a result. I switched to a Virtual Dynamics P3, and the problem went away.