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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
jea48
4,415 posts
 
I agree with Swampwalker. Good chance you have a ground loop hum caused by the CATV coax cable. Disconnect the coax temporary and see if that doesn't stop the hum.
thorman
1,262 posts
 
Try pulling the plug disconnecting the television from the circuit..It sounds like interference from having the stereo and television cable on the same circuit..You may need to seperate ( different dedicated lines ) the two..............
edmallia OP
1 posts
 
Dear Almarg,Swampwalker,Jea48 and Thorman,

Thank you all for your quick responses and great thoughts on the problem. First thing in the morning I will run down all of the suggested possibilities. Thanks for helping to make my traditional viewing of a Christmas Carol "Hum-Free"
Have a great holiday and to rob a line from a favorite movie of mine - May the best of your past be the worst of your future.
I'll post the results.
Thanks again.
weiserb's avatar
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weiserb
476 posts
 
You many have introduced a ground loop into the system by connecting the audio system to a Home Theater system, Cable TV box, and or powered subwoofer. The cable is ususally guilty followed by the Sub which usually gets pluged into a different outlet. I installed two isolation transformers from Jensen transformers (not cheap about $ 150+ each )My background is black as night now.

Unplug the above items to see if they are at fault when you plug them back in
hifigy
59 posts
 

I had the same problem with my PA-7 & CA-7. The hum was intoduced by the audio cables coming from anything connected to my cable tv system. This was the quick and cheap way to create an isolation transformer. Take 2 75ohm/300ohm transformers that come with vcrs or tvs. Hopefully you'll have one with pigtails (300ohm) and one with screw teminals. Connect the pigtails to the teminals. You'll now have two "f" connectors at either end. Connect one end to your cable feed and one to your video system. This was essentially what the old "Magic" box was from a few years back but, instead of $99, you've spent maybe $5.

Happy holidays
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