Do turntables always need a ground wire?

Discussion in 'Audio Hardware' started by bigmikerocks, Jan 11, 2011.

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  1. bigmikerocks

    bigmikerocks Forum Resident Thread Starter

    so i hooked a turntable up and turned on the power to the receiver and was getting this awful humming noise

    so i went to see if the ground wire was loose or not connected all the way...i jiggled it a little and it came totally off, and the humming stopped

    turntable sounds perfect WITHOUT the ground wire hooked up.

    what the hell?

    it's a thorens td160

    every other tt i've hooked through this receiver needs the ground wire connected to keep it from humming

    what could be up with this?
     
  2. stuwee

    stuwee Forum Resident

    Location:
    Tucson AZ
    Don't touch that dial!!

    It's called 'That Thorens Magic' :winkgrin: :cool:!! A ground is a loop of energy that needs a place to go, sometimes it needs help like the ground post. And sometimes it just does it's own thing, you have experienced the later Tex, I'm sure to get zapped for this explaination.......:D
     
  3. PMC7027

    PMC7027 Forum Hall Of Fame

    Sometimes a ground wire helps reduce hum and sometimes it can make it worse. If disconnecting the ground wire eliminated the hum don't worry about it. Does the TT have a 3 pronged plug? Sometimes that makes a difference in whether you need the ground wire.
     
  4. KT88

    KT88 Forum Resident

    Electrical devices need a ground to operate. That doesn't mean they need a separate ground wire though. The devices only need one ground path and any additional creates a "ground loop" and a 60hz hum (50hz in some countries). Phono cartridges can be grounded by their own pin outs into the RCA connectors or to the headshell and through the tonearm and into the turntable. Adding a ground wire to such a system creates a ground loop.
    -Bill
     
  5. bigmikerocks

    bigmikerocks Forum Resident Thread Starter

    this tt just has what looks like probably the original 2-pronged AC plug.

    totally hum free with the ground wire disconnected....guess i'll just run with it!
     
  6. Robin L

    Robin L Musical Omnivore

    Location:
    Fresno, California
    I'm using Carnare StarQuad, the ground shield is only connected to the SME III and the turntable, not the pre-amp. No hum.
     
  7. tommy-thewho

    tommy-thewho Forum Resident

    Location:
    detroit, mi
    If your not getting any hum leave it alone...
     
  8. No ground wire on the Thorens TD 160. You shouldn't get a hum unless you use a
    Grado cart. Even then it is hit and miss.
     
  9. misterdecibel

    misterdecibel Bulbous Also Tapered

    With the Grado the noise won't be ground hum, but induction noise from the AC motor picked up by the cartridge. At least that's what it is if the hum gets louder as the cartridge gets closer to the middle of the record.
     
  10. Senn20

    Senn20 Forum Resident

    Location:
    Madison, WI, US
    The distinction that needs to be made here is between signal ground and chassis ground.

    In equipment with poorly thought out grounding schemes they are one and the same.

    To operate equipment safely, you absolutely should have the chassis ground connected. Ask any guitarist who has ever gigged in seedy bars with an old amp!

    The thing that creates a ground loop is your home's wiring.

    I have an old Sherwood integrated that I installed a 3 prong plug on. It previously had a two prong plug which was not polarized, and I'd been zapped by it before. After installing the three prong plug there was an annoying hum, so I installed a ground lift switch and never ended up using chassis ground. At the very least the receiver had a properly polarized plug on it now.

    Thing is, I'm living in a different place now and there is absolutely no additional hum regardless of the position the ground lift switch is in.

    The best thing is to engage that chassis ground and track down where the ground loop occurs. If you have equipment in your systems hooked up to different outlets, that can do it. I had an old 70's Tascam mixer that I had to run a wire from the ground screw to the signal ground on my active monitors to get rid of the hum.

    What were you grounding the turntable to?
     
  11. KT88

    KT88 Forum Resident

    That's right. Also, the combining of signal ground with a turntables arm ground is perfectly good engineering. It actually helps to eliminate ground loops and reduce the noise floor in many designs. Phono stages are very sensitive to this, so it is often done to prevent noise. This is probably the reason that the arm has no hum now with the chassis ground wire disconnected. No noise means that the unit must be grounded properly or shielded properly. That's a good thing.
    -Bill
     
    MLutthans likes this.
  12. My turntable (a Denon DP-300F) doesn't have one, so I guess the answer to your original question is no.
     
  13. McLover

    McLover Forum Resident

    Location:
    East TN
    On the Thorens TD 160, the ground wire is not separate. It's part of the RCA cables. Same on the AR-XA turntable.
     
  14. david62

    david62 New Member

    Location:
    Rochester,N.Y.
    I converted my TD 145 to a seperate ground wire.I had to disconnect the ground from the right channel shield.I am still waitng for a belt,so I have not tried it yet.Hopefully I won't have any hum...
     
  15. Rhythmdoctor

    Rhythmdoctor Well-Known Member

    I have the same tt, just got it this summer and I'm getting a hum and no sound out of one speaker. I get sound out of both speakers if I go to radio or mono when listening to records. I'm at a loss about what could be wrong. But I will listen to suggestions.
     
  16. chervokas

    chervokas Forum Resident

    From what others have said here -- that the TD160 wasn't designed with a separate ground wire -- perhaps your table was modded at some point?

    It's my understanding that in a turntable, commonly, the ground wire is a connection between the tonearm tube and other such parts (like the bearing) to chassis ground -- things that aren't mechanically or electrcially connected to signal ground or any chassis typically because they're mounted to plastic or acrylic or wood subchasses. Grounding the arm tube allows it to act as a shield for the unsheilded wires running through it, and, if there's continuity from arm through screws to cartridge body, it will allow the cartridge body to act as a shield too. However if the turntable's motor chassis and metal chassis etc is at one potential, the phono preamp is at another potential and they're being connected via the turntable ground wire. Then you might have a loop problem.

    So if the Thorens originally was wired with a ground connection for the whole turntable via right signal wire (often turntables have the ground connection for these mechanical parts tied to signal ground with no separate wire) and someone added a separate ground connection without changing the original wiring scheme, well, could result in a loop. You can test for continutity between the RCA output ground sleeves and the arm tube, but it sounds like just running the table without the ground wire connection is working fine.
     
  17. Six String

    Six String Senior Member

    Switch the cables l and r leads (at both ends natch!) to see if it is just a bad interconnect. One of the two channels is getting through. if you use a stereo record with really different sounds in the l and r channels you should be able to tell if the one and only channel you do switched when you flipped the interconnects. That would also help you pinpoint the source of the problem. There are probably more knowledgeable people who will come along as well. Anytime I have what appears to be a possible bad connection, I unplug and reconnect everything in the problem's path. Sometimes it is as simple as that. Good luck.
     
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