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Cannot get rid of hum!!

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dustin2123

Active Member
I am at a loss trying to keep the hum at bay when using my TT. I've got a Dynaco st70 tube amp & a Pas 3 tube pre and I've grounded my turntable to one or the other with no success! It will go away for some time but it alway comes back. It's driving my nuts! Any recommendations?!
 
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dustin2123 said:
I am at a loss trying to keep the hum at bay when using my TT. I've got a Dynaco st70 tube amp & a Pas 3 tube pre and I've grounded my turntable to one or the other with no success! It will go away for some time but it alway comes back. It's driving my nuts! Any recommendations?!
Click to expand...

The clue is that it goes away at times, are you sure of that? Is any part of your system hooked to your TV or cable box?
 
really sounds like flaky connections somewhere. Does it do this on all inputs, or only the turntable? Have you tried cleaning or changing the cables and their connections ?
 
Hey there , sorry to hear this . Can I ask how close are your speakers are from the TT, did this just start or is this a new hook up? , the hum... it's only on phono source ? maybe check your head shell , is it better or worse if the stylus is down ?
I hate the hum , just hate it..
 
Ouch!

Good clue that :Coming and going - if we may take it literally? There are bound to come a host of reasons when one is not present to check each in tandem. All good logic so far.

My extra cents: What happens when you do not switch the turntable motor on, with the arm on the rest, or on a record (normal volume setting; beware of acoustic feedback!) What cartridge are you using, MM or MC? In the latter case (probably with a transformer), are you near any external sources of magnetic induction?

Then also, are you able to determine the hum frequency? 120 Hz (USA) will originate in a different way than 60 Hz, and you should be able to differentiate. (I hope you mean 'clean' hum, not the kind of singing of indeterminable pitch - the latter is different and might indicate a doubtful cable screen connection somewhere.

As said, so many options. Good luck!
 
Using a Ortofon 2M bronze on a Marantz 6200 thats been professionally serviced with new rca cables. Speakers are 5'feet away from TT. My Pas 3 has been professionally rebuild/modded/upgraded from James Fisher of FisherAMPS in Georgia. It has all new inputs on rear of unit. It only has a hum on the phono... although I havent tried another TT which I supposei could try.
 
really kind of sounds like a turntable or phono stage hum then.

If you have some spare RCA plugs, try this: Make yourself a couple of shorting connectors. Its just an RCA plug with the center lead connected to the outer shell. Plug those into the phono input on the PAS3 and see if the hum goes away. If it does, the issue is somewhere outside of the preamp. If it hums the same, then its internal to the preamp.
 
If nothing else works try an isolation transformer for the TT. I had a hum that I couldn't get rid of, got an isolation transformer, plugged the TT into it, hum gone.
 
1. Does any piece of equipment have a 3 prong power cord? If so, try grounding only the preamp, and put a 3 prong to 2 prong adapter on everything else.
2. If nothing has a 3 prong ground plug, try jumpering the preamp chassis to the house ground.
3. Try re-routing the phono cables away from AC cords. Make sure the turntable is not sitting on top of any piece of equipment.
4. When you touch the tonearm does the hum increase or decrease.
5. How much hum is this compared to the sound of the record playing? Do you have to walk up to your speakers to hear it?
6. If you put shorting plugs in the phono input do you hear the hum?
 
If I touch the tone arm it sounds as if everything is going exoplode haha. Slight hum in tnt background during music playing.
 
dustin2123 said:
I am at a loss trying to keep the hum at bay when using my TT. I've got a Dynaco st70 tube amp & a Pas 3 tube pre and I've grounded my turntable to one or the other with no success! It will go away for some time but it alway comes back. It's driving my nuts! Any recommendations?!
Click to expand...
First
Disconect the ground wire and don't use it, also get it out of the mix of wires, stash it under the table.
Second
Make sure your phono interconects are routed away from other cables.
Third
Put tape over the Phono RCA jacks not in use.
 
Touch the tonearm and get hum. Sure sounds like a bad connection at the cartridge or in the headshell mount.
 
Dirty headshell contacts?

tom3 said:
Touch the tonearm and get hum. Sure sounds like a bad connection at the cartridge or in the head-shell mount.
Click to expand...

I had a similar problem, the spring loaded contacts on my tone arm where making poor contact with the stud contacts on the head-shell, a SMALL amount of contact cleaner on both, followed by a wipe with a cotton swab fixed the problem for me. :yes:

BTW, you could get your multimeter and see that you have a good low resistance connection between the metal tone arm and your ground cable\base of the TT.

Mark T. :music:
 
markn2wae said:
I had a similar problem, the spring loaded contacts on my tone arm where making poor contact with the stud contacts on the head-shell, a SMALL amount of contact cleaner on both, followed by a wipe with a cotton swab fixed the problem for me. :yes:

BTW, you could get your multimeter and see that you have a good low resistance connection between the metal tone arm and your ground cable\base of the TT.

Mark T. :music:
Click to expand...

THIS. Touching the arm and getting hum means the arm tube is not grounded.
 
Are all tone arms grounded? I just tried teh resistance test from aluminum arm to ground wire from TT, reads open,,, however, I get a reading from teh top gimbal screw to teh ground wire...
Tried it on both Technics and Dual TTs, same results...
 
The arms are sometimes coated in something to keep them shiny and that might foul up readings. Try in the end where the headshell goes maybe. But yeah, typically there is a fifth wire going up the tube and it attaches to the arm tube itself somewhere internally.
 
Seems as tho,,, Tried again, can't read to teh aluminum tube, but can to teh screws holding teh cartridge mounts to teh grnd connection... So its grounded at least up to teh head...
 
I've been working on a pair of mono preamps for a while,,, just tried a few of teh ideas here on them, and realized the phono ground wire connected to teh power amp, seems to be teh quietest path to ground I found yet...
Of course, make sure teh ground is connected thru the arm of your TT, along with the previous thoughts...
 
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