help with humming noise?

I recently bought a nak ca7 and pa7 as a second system.when i hook those two components together, the speaker emit a humming noise. yet when i try cd direct to amp - no noise. then i use my ML 336 to ca 7 no noise. ml 380s to pa7 no noise. they are all using same source and ic/speaker cable.
I am confused
what's the problem ? more importantly, how can i fix it?
I'm not familiar with either component, but you might have a ground loop between them. Try floating the ground (using a cheater plug) on one of those components and see if that stops the hum. You might also want to mess with placement...just in case it's electrical interference between components. There are a million hum threads archived here, so you should do a search and see if you find your answer.
Yes,there are many threads on hums.

There are also a handful of reasons for hum in your setup with a number of valid and invalid resolutions.
Try grounding the CA7. You may have a grounding problem that goes away when you hook up a Nak to an ML component that is itself properly grounded. For example, the cable ground/drain on the MLs may be connected to chassis ground. Connecting the CA7 with the PA7 may not provide the same grounding solution. Run a wire from any chassis screw on the CA7 to a known good ground (start by trying any screw on a grounded ML component). If there's a little spark when you complete the connection, you may have a faulty electrical component in the Nak circuitry. This would require a professional service center to fix. If there's no little spark and the hum goes away, you're done.