2. amps-preamps
  3. 1230071394

Nakamichi PA-7 Hum

Hi,
Hope everyone has a great holiday season.
I am the original owner of a PA-7. If my house was ever robbed the first place I would look to know if my life, as I have known it, was over is my audio rack. I will stay with the PA-7 until it dies or I do.
My problem is that any new equipment that I try to run through the preamp (Nakamichi CA-5)that is not CD related i.e. cable TV audio lines, dvd players - anything new makes the amp hum. It is loud enough to be annoying but is drowned out when the volume is loud enough. Needless to say I have never left anything connected to it that caused it to hum for fear of doing damage.
Any ideas why it does that and if there is some type of line filter that I should have and don't know about? I would love to play DVD's, cable, etc. through the PA-7 but as long as I have had it only CD's play through without a problem.
Thanks for any help.
edmallia
swampwalker's avatar
swampwalker
5,138 posts
 
Yep, Hifigy is right. Its an easy way to check to see if that is the problem, since most of us have dozens of those little buggers lying around in a drawer somewhere. I then went and got the $10 RS isolation tranny which of course looks a lot neater.
marakanetz's avatar
marakanetz
5,473 posts
 
With time the internal power supply of the amp may become noisy due to the lack of DC filtering. If this is the case you'll need to inspect PCB for the loose soldering joints and replace power supply electrolytic capacitors.
almarg's avatar
Ag insider logo xs@2x
almarg
9,670 posts
 
With time the internal power supply of the amp may become noisy due to the lack of DC filtering. If this is the case you'll need to inspect PCB for the loose soldering joints and replace power supply electrolytic capacitors.

Very true, but in this case he said that the problem does not exist when he selects a cd player with his preamp, while it does exist when he selects other line-level inputs.

Which tells me the problem is unlikely to be internal to his power amp, or to his preamp for that matter. I think it's more likely to be an open return path (shield connection) in an interconnect, or one of the other things I mentioned above.

Or, as others have said, a ground loop with the catv system IF the problem only occurs when there is a connection to something within that system (which I suspect is not the case based on the wording of his original post).

Regards,
-- Al
More to discover