Root cause for hum

I have had a hum problem for some time but never considered it a big deal.

I decided to track it down. It was very noticeable when I turned on the Marantz SA8500. After disconnecting and reconnecting RCA cables and power cords I found that the hum is coming from the TV/monitor via HDMI to my Quantum Byte computer which is connected to the Marantz via USB.

With HDMI disconnected everything is dead quiet. For now I have to keep the HDMI disconnected unless I need the TV/monitor when tweaking the computer. This is not a huge deal because this computer is music only and I am using Jriver's Gizmo for control.

What I did not expect is that a little hum goes a long way in degrading SQ. My system sounds better than ever :)
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Comments

  • tonybtonyb Posts: 27,202
    edited October 2016
    That's why there are so many products out there to get rid of signal noise. Have you tried using a better HDMI cable ? Try a cheater plug on the TV ?
  • gcegce Posts: 2,035
    Also try leaving the HDMI cable hooked to your computer. Disconnect the cable coming into your house that goes to your cable box or TV and see if the hum goes away.

    If the hum goes away there's a fix for that.
  • machonemachone Posts: 693
    I have not tried a better HDMI. I believe the current one is Blue Jeans. I did try the cheater plug on several components.

    I will try disconnecting the cable going to the cable box and see what happens.
    Thanks
  • ParadoxexParadoxex Posts: 196
    My understanding is that you should always start with the coax cable, as that's the primary source of hum. It was for my system when I first set it up. I was literally doubting my investment before I figured out the issue. 60hz hum out of an SVS PC-13 = not a good problem to have.
  • pitdogg2pitdogg2 Posts: 6,565
    Paradoxex wrote: »
    60hz hum out of an SVS PC-13 = not a good problem to have.
    Yea that gets old fast lol .
  • gmcmangmcman Posts: 779
    I had a slight hum with my cable box plugged into my Panamax power conditioner. Tried different power cords on the preamp, amp, triple checked everything.

    Once I removed the cable box power cord from the Panamax and used the wall outlet, all was good. Not sure exactly why but that was the cause.
  • machonemachone Posts: 693
    gce wrote: »
    Also try leaving the HDMI cable hooked to your computer. Disconnect the cable coming into your house that goes to your cable box or TV and see if the hum goes away.

    If the hum goes away there's a fix for that.

    I found that the source of the hum is the cable tv.
    So what is the fix for this?
    Thanks
  • gcegce Posts: 2,035
    Put one of these between the cable coming into your home and your cable box. There are a few different brands but this one should do the trick.

    https://www.amazon.com/Viewsonics-VSIS-EU-Cable-Ground-Isolator/dp/B0017I3K9M
  • machonemachone Posts: 693
    Thanks gce
  • tonybtonyb Posts: 27,202
    machone wrote: »
    gce wrote: »
    Also try leaving the HDMI cable hooked to your computer. Disconnect the cable coming into your house that goes to your cable box or TV and see if the hum goes away.

    If the hum goes away there's a fix for that.

    I found that the source of the hum is the cable tv.
    So what is the fix for this?
    Thanks

    A decent power conditioner.

    Usually there is a grounding stake right where the cable enters the house. You can try cleaning that up some at the contact points.
  • machonemachone Posts: 693
    Yes.
    I need to look at the grounding rods first.
  • machonemachone Posts: 693
    The cable ground wire connector was loose on the main ground wire. I tightened it and it helped but did not eliminate it entirely.
  • maandjojomaandjojo Posts: 290
    I had a nasty hum, I googled it and found a solution that worked for me. Be sure that all your electronics are plugged into the same wall outlet. You can pigtail power strips but the last one would go to the wall out let. Immediately did the trick.

    Joe
  • tonybtonyb Posts: 27,202
    machone wrote: »
    The cable ground wire connector was loose on the main ground wire. I tightened it and it helped but did not eliminate it entirely.

    Just tightening it up won't do the trick. You would need to take it apart and go over it with some fine sand paper to remove the oxidation on the stake and any connecting parts. That may or may not solve the problem completely.

    Use a power conditioner and run the cable through it. Make sure your using quality cables in your system and not the Walmart stuff or red and white cables that came with any of the gear.

    Ground loop hum is basically too many grounds in one spot, if you can, split whats powered onto 2 different outlets. You can also buy a cheater plug for 2 bucks at any hardware store and use that on various pieces until the hum goes away. A cheater plug removes the ground by turning a 3 prong power cord into a 2 prong. I would try it first on the receiver.
  • machonemachone Posts: 693
    Thanks Tony. I'll clean up the connection. I am using a cheater plug on my turntable as a temp fix.
  • Msabot1Msabot1 Posts: 1,723
    Machone...remember,you can't cover up a stink by using something that smells nice....Forget the quick fixes and gadgets..track down the source of the noise and eliminate it....
  • steveinazsteveinaz Posts: 17,657
    edited January 12
    Cable TV/Satellite induced hum usually cannot be "fixed" in the traditional sense. It's a difference in ground potential between your home AC and the cable system; however it can be worked around, reduced, and even eliminated depending on your source. I got around my DirecTV hum by using fiber opt (toslink) out to my DAC. Fiber completely eliminates the galvonic connection. I tried the whole clean-up the ground wire, tighten connection, make sure everything is powered by the same outlet, etc, etc...the hum remained. Toslink fixed it. TV audio now is outstanding. If you only have dig coax out on your Sat/Cable Box, spend $19 and get a coax to toslink converter from Monoprice.

    Also, sometimes 2-pronged AC equipment (typical on some BluRay/DVD players) can conflict with 3-pronged (passing the ground) equipment, and produce hum. These issues can be even harder to cure.
  • RamZetRamZet Posts: 776
    steveinaz wrote: »
    Cable TV/Satellite induced hum usually cannot be "fixed" in the traditional sense. It's a difference in ground potential between your home AC and the cable system; however it can be worked around, reduced, and even eliminated depending on your source. I got around my DirecTV hum by using fiber opt (toslink) out to my DAC. Fiber completely eliminates the galvonic connection. I tried the whole clean-up the ground wire, tighten connection, make sure everything is powered by the same outlet, etc, etc...the hum remained. Toslink fixed it. TV audio now is outstanding. If you only have dig coax out on your Sat/Cable Box, spend $19 and get a coax to toslink converter from Monoprice.

    Also, sometimes 2-pronged AC equipment (typical on some BluRay/DVD players) can conflict with 3-pronged (passing the ground) equipment, and produce hum. These issues can be even harder to cure.

    Ground the main cable feed coming into the house.
    Do it within 4 feet of entry.

    https://www.amazon.com/gp/aw/d/B00CLFGH40/ref=mp_s_a_1_6?ie=UTF8&qid=1484257756&sr=8-6&pi=AC_SX236_SY340_QL65&keywords=coax+ground&dpPl=1&dpID=51ufJjGsFWL&ref=plSrch

    No ground?
    Use a cold water pipe.
    https://www.amazon.com/gp/aw/d/B00JIZ303W/ref=mp_s_a_1_3?ie=UTF8&qid=1484257878&sr=8-3&pi=AC_SX236_SY340_QL65&keywords=cold+water+pipe+ground&dpPl=1&dpID=514r-8RdM-L&ref=plSrch

    Connect with solid core grounding cable (the green stuff).
  • machonemachone Posts: 693
    I put the isolator on the cable and it eliminated that hum source. There is still some hum in the phono circuit but only at 12 o'clock or higher. I did move the power cable for the turntable from the power strip to the preamp closer to the turntable ground wire.
  • machonemachone Posts: 693
    I found a source of mechanical hum.
    After turning everything in the garage off there was still mechanical hum. It's the garage door opener! It must have a noisy transformer. I might put a switch in the circuit to disconnect its power.
  • machonemachone Posts: 693
    I fixed the garage door opener circuit. I replaced the duplex outlet with a switched outlet. During listening sessions I can turn it off with a broom handle

    vmlcu6pbvpea.jpg
  • machonemachone Posts: 693
    OK, so I have changed all of the AC circuits to my system and still have one source of hum and it's a humdinger.

    During this investigation I isolated the Quantum Byte's power supply (Mojo v5) using a cheater plug. This had no affect on the hum.

    If you look at my signature you can see the path the signal takes to the preamp. Without the USB from the Quantum Byte (computer) to the Marantz plugged in it is dead quiet. Plug in the USB and there is hum, not a lot but it's there. There is also a HDMI connection between the Quantum Byte and the TV (used as a monitor during Jriver setup, etc). If I disconnect the HDMI the hum disappears.

    This make sense until I decided to start unplugging all of the other cables that go to the TV. I mean all of them including the the AC cord. With the TV completely disconnected floating in air I get hum when I connect the HDMI cable between the TV and the Quantum Byte.

    Where's the loop?

    It's all academic because I rarely use the TV as monitor and I can unplug the HDMI when not need but W-T-F.
  • tonybtonyb Posts: 27,202
    Maybe a bad cable in there ? Try the cheater plug on the Marantz ?
  • gmcmangmcman Posts: 779
    Do you have a cable coax plugged in anywhere? If so, try disconnecting the RG-6 from the receiver, you may also need to unplug any other RG-6 TV cables elsewhere in your home.
  • machonemachone Posts: 693
    Anything is possible. The Marantz does not have a third pin.
    I have an isolation t-former on the RG-6 TV cable in this room but not the whole house.
  • gmcmangmcman Posts: 779
    I would disconnect any RG-6 cable in your home to troubleshoot your issue.
  • pitdogg2pitdogg2 Posts: 6,565
    On Cable ground problems. IF it is a cable company and not Direct or Dish I have been able to re-terminate the F-connector and NOT use the braided shield or mylar under the F connector. This removes the ground at the source. SteveinAZ has a solid plan there by converting to optical. I had to do something exactly like that on an old receiver that only had one connector of each for digital. My coax became a optical so both could be used on the receiver. Up until 3months ago I still had it but tossed it out with other legacy items we no longer seem to use anymore.
  • machonemachone Posts: 693
    pitdogg2 wrote: »
    On Cable ground problems. IF it is a cable company and not Direct or Dish I have been able to re-terminate the F-connector and NOT use the braided shield or mylar under the F connector. This removes the ground at the source. SteveinAZ has a solid plan there by converting to optical. I had to do something exactly like that on an old receiver that only had one connector of each for digital. My coax became a optical so both could be used on the receiver. Up until 3months ago I still had it but tossed it out with other legacy items we no longer seem to use anymore.

    You reterminated were the cable enters the house?
  • pitdogg2pitdogg2 Posts: 6,565
    edited June 2
    end that goes to TV or Receiver. Personally I was told by more than one installer in the know that going through surge protectors they can drop the signal by as much as 3db and a drop of 1db can have a very negative affect. I use dish and was having signal problems it turned out that my furman surge protector had affected the signal by almost 2db. I could not do what I'm suggesting here because the ground shield is used as a return loop for the 18v going from the LNB to the Dish receiver. On standard Comcast type it is something that usually can be done to lift the ground at the end point Receiver,TV or surge protector. Signal should still flow through the conductor.

    If you have extra coax Rg6 laying around make an end 12"-16" long use a coax to coax connector so you can try it without doing the main cable. usually you cut and strip the cable fold the mylar and braided shield back over the cable jacket and compress your end on. The folded braided wire and mylar make your ground. Keeping that trimmed under the jacket you will no longer have that as ground.
  • maandjojomaandjojo Posts: 290
    I eliminated a hum I had by making sure I had all power sources connected through the same outlet. If it means using more than one multi outlet surge protector is fine as long as they are piggybacked.

    Joe
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