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Almighty TT hum --- help

I have seached the archives on the topic of turntable hum and found some info, but nothing that helps my situation, so here goes...I just ressurected an old (23 years) Technics turntable with an Audio Technica cartridge (...I know --- decidedly LOW FI, but I have young kids that suck up virtually all of my time and money). I am aching to get back into vinyl and I just wanted to see what the old table sounded like on the NAD 3020 I bought a couple of years ago. Holy hum, Batman!! Sounds like bad grounding, but I checked and cleaned all connections and that didn't help. The hum is only slightly louder when the ground wire is disconnected altogether. I would like to determine if my old TT is to blame or the old NAD. Any suggestions on my next step would be greatly appreciated.
wdhsvbgod
rockvirgo
587 posts
 
My old time TT went humming in one channel a while back and it turned out to be defective interconnects. If your hum is in both channels your problem likely lies elsewhere.
dan_ed
2,451 posts
 
What does it sound like with the cartridge disconnected?
wdhsvbgod OP
22 posts
 
Thanks for the responses...I just got a chance to do some more investigation today. Here are the results.

1. Using both line level sources (aux and tuner), the hum was still present, as loud and persistant as before.

2. I checked all connections to the cartridge and they appear and feel solid.

3. The hum is both channels, but using headphones, I realized that it is about 50% louder in one channel (left).

4. I disconnected the cartridge entirely and the hum sounded exactly the same.

5. I also found out (accidentally) that the hum was reduced in volume whenever I touched the amp. Does this imply a grounding problem?

I will take off the cover of the amp and see if the phono input jacks have been damaged in some way. Any other suggestions would help. I'd like to think that the TT is the problem (that way MAYBE I can justify buying a new one). I have heard that the 3020 has a good phono stage for its low cost and I definitely had that in mind when I bought it.
rockvirgo
587 posts
 
While my TT was humming one channel, leaving the interconnects hooked up but unplugging the TT from the wall made it go away. Replacing the TT's worn RCA females didn't help. Renewing the interconnects did.

Since you've got hum on any source it sounds like the amp is the misbehaver. Maybe your amp was in storage/left unpowered for a long time?

I stowed an OK-fine SS Dynaco 120 power amp in a hot Dallas attic. A couple of years later, it powered up and still worked but the transformer hummed in the chassis. Tightening the hold down bolts didn't help. That amp had failed two times prior (over one 8 cent and one 15 cent part respectively), so my solution was to sell it at half its value to someone who was willing to isolate the hum's exact cause. Sorry it's not much help. How attached are you to the NAD?
wdhsvbgod OP
22 posts
 
It seems I may have misrepresented what is going on here. My cdp and tuner work perfectly with this old NAD and have since I bought it. I actually connected the TT to the tuner and aux sources and the hum was still there (got to be the TT, right?). I still have not investigated the possibility of damaged phono input jacks, but the hum just reeks of a grounding problem to me, but I can't see any problem. I'd love to borrow someone else's TT, but I don't know anyone who has one (sad, isn't it?). That way I would be sure to know which was the culprit that was causing this hum.
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