Ground Loop Hum

Polkitup2
Polkitup2 Posts: 1,621
edited March 2010 in Electronics
I added a separate amp to my system and now I have a 60 hz hum. The hum disappers completey if I disconnect the front speaker pre-outs from my receiver to the HT bypass inputs on my pre-amp. I tried numerous different scenarios using different circuits, trying everything on the same dedicated circuit, different cables, unplugging everything, cheater plug, etc. Depending on what I did, I could increase the hum or lower the hum but never get rid of it entirely unless I either unplugged the RCA cable from my reciever to the HT bypass input on the pre-amp, or used a cheater plug on the new amp. Doing either of these would give me dead silence but of course I would like to use the HT bypass and I am not sure it's safe to run the amp with a cheater plug. I guess I was somewhat surprised that when I had all components connected to one power center on one dedicated circuit I still got a slight hum. Any ideas on how to fix this?
Post edited by Polkitup2 on
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Comments

  • RuSsMaN
    RuSsMaN Posts: 17,987
    edited March 2010
    The hum is more than likely related to a video source. Start disconnecting them one by one, Satellite, cable, playstation, etc to see where the issue(s) are.

    Cheers,
    Russ
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
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  • dpowell
    dpowell Posts: 3,067
    edited March 2010
    Try unplugging the coax cable from your cable TV box and see if it clears up. If so, you may need to grab a Jensen ISO-MAX VRD-1FF. Did the trick for my system.
    ____________________________________________________________

    polkaudio Fully Modded SDA SRS 1.2TLs + Dreadnaught, LSiM706c, 4 X Polk Surrounds + 4 X ATMOS, SVS PB13 Ultra X 2, Pass Labs X1, Marantz 7704, Bob Carver Crimson Beauty 350 Tube Mono Blocks, Carver Sunfire Signature Cinema Grande 400x5, ADCOM GFA 7807, Panasonic UB420, Moon 380D DAC, EPSON Pro Cinema 6050
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  • Polkitup2
    Polkitup2 Posts: 1,621
    edited March 2010
    Yep, I forgot that I had the cable feed running through the power center. I disconnected it and 99% of the hum went away. So now now I can either not have cable, not be able to use HT bypass, or run with a cheater plug on my amp :D
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  • Polkitup2
    Polkitup2 Posts: 1,621
    edited March 2010
    Good idea on the Jensen, that's sounds like my best option. Thanks guys!
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  • dpowell
    dpowell Posts: 3,067
    edited March 2010
    No prob. Don't know if you use Bing Cashback but I found a new Jensen on Ebay for around $45 plus a few bucks for shipping and used Bing to get 8% cashback.

    Here's the listing I bought from. No affiliation.
    http://cgi.ebay.com/CABLE-TV-GROUND-LOOP-ISOLATOR-JENSEN-ISO-MAX-VRD-1FF_W0QQitemZ380190677882QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5885215b7a

    BTW, he has best offer but I made 3 offers and they were all automatically rejected. My highest offer was $40 and at that point, I got more savings from using Buy It now with the cashback.
    ____________________________________________________________

    polkaudio Fully Modded SDA SRS 1.2TLs + Dreadnaught, LSiM706c, 4 X Polk Surrounds + 4 X ATMOS, SVS PB13 Ultra X 2, Pass Labs X1, Marantz 7704, Bob Carver Crimson Beauty 350 Tube Mono Blocks, Carver Sunfire Signature Cinema Grande 400x5, ADCOM GFA 7807, Panasonic UB420, Moon 380D DAC, EPSON Pro Cinema 6050
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  • hearingimpared
    hearingimpared Posts: 21,137
    edited March 2010
    Just to add to the above suggestions, I've had ground loop issues in the past that were resolved with better ICs all around. This is especially true of using a step-up transformer in the turntable path. Although this wasn't so much a ground loop hum it was a 60 cycle hum and I was able to eliminate it using MIT Shotgun S3s and with Joe Abrams' suggestion of twisting 8 twists into the pair really got rid of the hum.
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  • phipiper10
    phipiper10 Posts: 955
    edited March 2010
    I used this to solve the cabel hum

    http://www.parts-express.com/pe/showdetl.cfm?Partnumber=180-075
    Analog Source: Rega P3-24 Exact 2 w/GT delrin platter & Neo TT-PSU Digital Source: Lumin T2 w/Roon (NUC) DAC: Denafrips Pontus II Phono Preamp: Rega Aria MK3 Preamp: Rogue RP-7 Amp: Pass X150.8 Speakers: Joseph Audio Perspective 2, Audio Physic Tempo Plus Cables: Morrow M4 ICs & Audio Art SC-5 ePlus, Shunyata PCs Misc: Shunyata Hydra Delta D6, VTI rack, GIK acoustic panels
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